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Eyring, Nicholas J. "Development and Validation of an Automated Directivity Acquisition System Used in the Acquisition, Processing, and Presentation of the Acoustic Far-Field Directivity of Musical Instruments in an Anechoic Space." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4004.
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A high spatial resolution acoustic directivity acquisition system (ADAS) has been developed to acquire anechoic measurements of the far field radiation of musical instruments that are either remote controlled or played by musicians. Building upon work performed by the BYU Acoustic Research Group in the characterization of loudspeaker directivity, one can rotate a musical instrument with sequential azimuthal angle increments under a fixed semicircular array of microphones while recording repeated notes or sequences of notes. This results in highly detailed and instructive directivity data presented in the form of high-resolution balloon plots. The directivity data and corresponding balloon plots may be shown to vary as functions of time or frequency. This thesis outlines the development of a prototype ADAS and its application to different sources including loudspeakers, a concert grand piano, trombone, flute, and violin. The development of a method of compensating for variations in the played amplitude at subsequent measurement positions using a near-field reference microphone and Frequency Response Functions (FRF) is presented along with the results of its experimental validation. This validation involves a loudspeaker, with known directivity, to simulate a live musician. It radiates both idealized signals and anechoic recordings of musical instruments with random variations in amplitude. The concept of coherence balloon maps and surface averaged coherence are introduced as tools to establish directivity confidence. The method of creating composite directivities for musical instruments is also introduced. A composite directivity comes from combining the directivities of all played partials to approximate what the equivalent directivity from a musical instrument would be if full spectral excitation could be used. The composite directivities are derived from an iterative averaging process that uses coherence as an inclusion criterion. Sample directivity results and discussions of experimental considerations of the piano, trombone, flute, and violin are presented. The research conducted is preliminary and will be further developed by future students to expand and refine the methods presented here.
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Johnston, Ann. "Markov Bases for Noncommutative Harmonic Analysis of Partially Ranked Data." Scholarship @ Claremont, 2011. http://scholarship.claremont.edu/hmc_theses/4.
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Given the result $v_0$ of a survey and a nested collection of summary statistics that could be used to describe that result, it is natural to ask which of these summary statistics best describe $v_0$. In 1998 Diaconis and Sturmfels presented an approach for determining the conditional significance of a higher order statistic, after sampling a space conditioned on the value of a lower order statistic. Their approach involves the computation of a Markov basis, followed by the use of a Markov process with stationary hypergeometric distribution to generate a sample.This technique for data analysis has become an accepted tool of algebraic statistics, particularly for the study of fully ranked data. In this thesis, we explore the extension of this technique for data analysis to the study of partially ranked data, focusing on data from surveys in which participants are asked to identify their top $k$ choices of $n$ items. Before we move on to our own data analysis, though, we present a thorough discussion of the Diaconis–Sturmfels algorithm and its use in data analysis. In this discussion, we attempt to collect together all of the background on Markov bases, Markov proceses, Gröbner bases, implicitization theory, and elimination theory, that is necessary for a full understanding of this approach to data analysis.
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Manna, Utpal. "Harmonic and stochastic analysis aspects of the fluid dynamics equations." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1414120661&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Akman, Murat. "On the Dimension of a Certain Measure Arising from a Quasilinear Elliptic Partial Differential Equation." UKnowledge, 2014. http://uknowledge.uky.edu/math_etds/12.
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We study the Hausdorff dimension of a certain Borel measure associated to a positive weak solution of a certain quasilinear elliptic partial differential equation in a simply connected domain in the plane. We also assume that the solution vanishes on the boundary of the domain. Then it is shown that the Hausdorff dimension of this measure is less than one, equal to one, greater than one depending on the homogeneity of the certain function. This work generalizes the work of Makarov when the partial differential equation is the usual Laplace's equation and the work of Lewis and his coauthors when it is the p-Laplace's equation.
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Wiswall, Wendy Jeanne. "Partial vowel harmonies as evidence for a Height Node." Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185697.
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In this dissertation I examine partial vowel assimilations, where more than one but less than all vowel features pattern together in a phonological rule. The result of this dissertation research is the 'Height Node Geometry'. The particular innovation this geometry makes is to group the height features ( (high) and (low)) under a separate Height Node, as opposed to having the height features report to the Dorsal Node or the Place Node. Motivation for the Height Node Geometry comes from analyses of several phonological processes. First, removing the height features from under the Dorsal Node and the Place Node facilitates a more natural explanation for reduplication in the Petit Diboum dialect of Fe?fe?-Bamileke. Second, placing the height features above the Place Node but still directly or indirectly under the Supralaryngeal Node provides an account for Tunica partial translaryngeal harmony. Finally, vowel harmony in Ewe involves spreading of (+high) and (+low) in the same environment, arguing for a simpler rule of node spread; hence, I propose that the height features stem from a separate Height Node, instead of directly to the Supralaryngeal Node.
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Branding, Volker. "The evolution equations for Dirac-harmonic Maps." Phd thesis, Universität Potsdam, 2012. http://opus.kobv.de/ubp/volltexte/2013/6420/.
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This thesis investigates the gradient flow of Dirac-harmonic maps. Dirac-harmonic maps are critical points of an energy functional that is motivated from supersymmetric field theories. The critical points of this energy functional couple the equation for harmonic maps with spinor fields. At present, many analytical properties of Dirac-harmonic maps are known, but a general existence result is still missing.
In this thesis the existence question is studied using the evolution equations for a regularized version of Dirac-harmonic maps. Since the energy functional for Dirac-harmonic maps is unbounded from below the method of the gradient flow cannot be applied directly. Thus, we first of all consider a regularization prescription for Dirac-harmonic maps and then study the gradient flow.
Chapter 1 gives some background material on harmonic maps/harmonic spinors and summarizes the current known results about Dirac-harmonic maps. Chapter 2 introduces the notion of Dirac-harmonic maps in detail and presents a regularization prescription for Dirac-harmonic maps. In Chapter 3 the evolution equations for regularized Dirac-harmonic maps are introduced. In addition, the evolution of certain energies is discussed. Moreover, the existence of a short-time solution to the evolution equations is established.
Chapter 4 analyzes the evolution equations in the case that the domain manifold is a closed curve. Here, the existence of a smooth long-time solution is proven. Moreover, for the regularization being large enough, it is shown that the evolution equations converge to a regularized Dirac-harmonic map. Finally, it is discussed in which sense the regularization can be removed.
In Chapter 5 the evolution equations are studied when the domain manifold is a closed Riemmannian spin surface. For the regularization being large enough, the existence of a global weak solution, which is smooth away from finitely many singularities is proven. It is shown that the evolution equations converge weakly to a regularized Dirac-harmonic map. In addition, it is discussed if the regularization can be removed in this case.Die vorliegende Dissertation untersucht den Gradientenfluss von Dirac-harmonischen Abbildungen. Dirac-harmonische Abbildungen sind kritische Punkte eines Energiefunktionals, welches aus supersymmetrischen Feldtheorien motiviert ist. Die kritischen Punkte dieses Energiefunktionals koppeln die Gleichung für harmonische Abbildungen mit Spinorfeldern. Viele analytische Eigenschaften von Dirac-harmonischen Abbildungen sind bereits bekannt, ein allgemeines Existenzresultat wurde aber noch nicht erzielt. Diese Dissertation untersucht das Existenzproblem, indem der Gradientenfluss von einer regularisierten Version Dirac-harmonischer Abbildungen untersucht wird. Die Methode des Gradientenflusses kann nicht direkt angewendet werden, da das Energiefunktional für Dirac-harmonische Abbildungen nach unten unbeschränkt ist. Daher wird zunächst eine Regularisierungsvorschrift für Dirac-harmonische Abbildungen eingeführt und dann der Gradientenfluss betrachtet. Kapitel 1 stellt für die Arbeit wichtige Resultate über harmonische Abbildungen/harmonische Spinoren zusammen. Außerdem werden die zur Zeit bekannten Resultate über Dirac-harmonische Abbildungen zusammengefasst. In Kapitel 2 werden Dirac-harmonische Abbildungen im Detail eingeführt, außerdem wird eine Regularisierungsvorschrift präsentiert. Kapitel 3 führt die Evolutionsgleichungen für regularisierte Dirac-harmonische Abbildungen ein. Zusätzlich wird die Evolution von verschiedenen Energien diskutiert. Schließlich wird die Existenz einer Kurzzeitlösung bewiesen. In Kapitel 4 werden die Evolutionsgleichungen für den Fall analysiert, dass die Ursprungsmannigfaltigkeit eine geschlossene Kurve ist. Die Existenz einer Langzeitlösung der Evolutionsgleichungen wird bewiesen. Es wird außerdem gezeigt, dass die Evolutionsgleichungen konvergieren, falls die Regularisierung groß genug gewählt wurde. Schließlich wird diskutiert, ob die Regularisierung wieder entfernt werden kann. Kapitel 5 schlussendlich untersucht die Evolutionsgleichungen für den Fall, dass die Ursprungsmannigfaltigkeit eine geschlossene Riemannsche Spin Fläche ist. Es wird die Existenz einer global schwachen Lösung bewiesen, welche bis auf endlich viele Singularitäten glatt ist. Die Lösung konvergiert im schwachen Sinne gegen eine regularisierte Dirac-harmonische Abbildung. Auch hier wird schließlich untersucht, ob die Regularisierung wieder entfernt werden kann.
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Brown, John. "A SPACE BASED PARTICLE DAMPER DEMONSTRATOR." DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/501.
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The structure and payload of a CubeSat flight experiment that investigates the performance of particle dampers in a micro-gravity environment was designed, built, and tested, and will provide on orbit data for model validation and improved performance predictions for space applications of particle damping.
A 3-D solid model of the integrated CubeSat structure and payload was created satisfying all constraints from CubeSat and the System Dynamics Department at Northrop Grumman Aerospace Systems. The model was verified using commercially available Finite Element Analysis software (FEA), and a prototype structure part was fabricated. The prototype was tested and verified the FEA. A complete subassembly ready for flight was manufactured as an engineering unit and tested to space qualification loads of both launch vibration and thermal vacuum. Two additional units were contracted out for manufactured to serve as the flight unit and backup, and are currently ready for launch.
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Yang, Danyu. "Partial sum process of orthogonal series as rough process." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:f48d69b9-29ba-420b-a6b5-55deba847b15.
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In this thesis, we investigate the pathwise regularity of partial sum process of general orthogonal series, and prove that the partial sum process is a geometric 2-rough process under the same condition as in Menshov-Rademacher Theorem. For Fourier series, the condition can be improved, and an equivalent condition on the limit function is identified.
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Wiswall, Wendy J. "Tunica Partial Vowel Harmony as Support for a Height Node." Department of Linguistics, University of Arizona (Tucson, AZ), 1991. http://hdl.handle.net/10150/227242.
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Bergeron, Mario. "Coherent state path integral for the harmonic oscillator and a spin particle in a constant magnetic field." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/27391.
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The definition and formulas for the harmonic oscillator coherent states and spin coherent states are reviewed in detail. The path integral formalism is also reviewed with its relation and the partition function of a sytem is also reviewed. The harmonic oscillator coherent state path integral is evaluated exactly at the discrete level, and its relation with various regularizations is established. The use of harmonic oscillator coherent states and spin coherent states for the computation of the path integral for a particle of spin s put in a magnetic field is caried out in several ways, and a careful analysis of infinitesimal terms (in 1/N where TV is the number of time slices) is done explicitly. The theory of the magnetic monopole and its relation with the spin system are explained, and the equivalence of these two system is established up to infinitesimal order by the introduction of an exterior interaction to the monopole. This gives a new representation of a coherent state path integral in terms of a more familiar Feynman path integral. The coefficient of the topological term in the spin system appears explicitly without ambiguity, as being 2s.Science, Faculty of
Physics and Astronomy, Department of
Graduate
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McDermott, Matthew. "Fast Algorithms for Analyzing Partially Ranked Data." Scholarship @ Claremont, 2014. http://scholarship.claremont.edu/hmc_theses/58.
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Imagine your local creamery administers a survey asking their patrons to choose their five favorite ice cream flavors. Any data collected by this survey would be an example of partially ranked data, as the set of all possible flavors is only ranked into subsets of the chosen flavors and the non-chosen flavors. If the creamery asks you to help analyze this data, what approaches could you take? One approach is to use the natural symmetries of the underlying data space to decompose any data set into smaller parts that can be more easily understood. In this work, I describe how to use permutation representations of the symmetric group to create and study efficient algorithms that yield such decompositions.
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Fernandes, Ricardo Augusto Souza. "Localização e identificação de consumidores com alta contribuição para a distorção harmônica de tensão em sistemas de distribuição." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-08092011-160635/.
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Esta tese consiste em apresentar um método para localização e identificação de consumidores com alta contribuição para a distorção harmônica de tensão medida em subestações de sistemas de distribuição de energia elétrica. Cabe comentar que a etapa de localização visa obter uma lista das possíveis posições onde possa estar alocado o consumidor que possua cargas não lineares com grande consumo de potências harmônicas. Partindo-se desta lista, realiza-se a etapa de identificação, em que são estimadas as amplitudes de cada harmônica na posição selecionada. Por fim, um algoritmo para ajuste/sintonia do método de localização é empregado com o intuito de se realizar uma possível correção com relação à posição do consumidor. Desta forma, por meio de estudos de caso (simulados), os resultados obtidos procuram validar a metodologia proposta.This thesis provides a method for location and identification of consumers with larger contribution to harmonic distortion of voltage in power distribution substations. It is worth to mention that the stage of consumers location must furnish a list of possible positions where there may be consumers, who have nonlinear loads with high consumption of harmonic power. From this list, the identification stage is performed in order to estimate the amplitude of each harmonic from the location selected. Finally, a method for improve the location algorithm is employed in order to refine the consumer position. Therefore, by means of simulated case studies, the results obtained for these stages seek to validate the methodology proposed.
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Barker, Tobias. "Uniqueness results for viscous incompressible fluids." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:db1b3bb9-a764-406d-a186-5482827d64e8.
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First, we provide new classes of initial data, that grant short time uniqueness of the associated weak Leray-Hopf solutions of the three dimensional Navier-Stokes equations. The main novelty here is the establishment of certain continuity properties near the initial time, for weak Leray-Hopf solutions with initial data in supercritical Besov spaces. The techniques used here build upon related ideas of Calderón. Secondly, we prove local regularity up to the at part of the boundary, for certain classes of solutions to the Navier-Stokes equations, provided that the velocity field belongs to L∞(-1; 0; L3, β(B(1) ⋂ ℝ3 +)) with 3 ≤ β < ∞. What enables us to build upon the work of Escauriaza, Seregin and Šverák [27] and Seregin [100] is the establishment of new scale-invariant estimates, new estimates for the pressure near the boundary and a convenient new ϵ-regularity criterion. Third, we show that if a weak Leray-Hopf solution in ℝ3 +×]0,∞[ has a finite blow-up time T, then necessarily limt↑T||v(·, t)||L3,β(ℝ3 +) = ∞ with 3 < β < ∞. The proof hinges on a rescaling procedure from Seregin's work [106], a new stability result for singular points on the boundary, suitable a priori estimates and a Liouville type theorem for parabolic operators developed by Escauriaza, Seregin and Šverák [27]. Finally, we investigate a notion of global-in-time solutions to the Navier- Stokes equations in ℝ3, with solenoidal initial data in the critical Besov space ?-1/44,∞(ℝ3), which has certain continuity properties with respect to weak* convergence of the initial data. Such properties are motivated by the strategy used by Seregin [106] to show that if a weak Leray-Hopf solution in ℝ3×]0,∞[ has a finite blow-up time T, then necessarily limt↑T ||v(·, t)||L3(ℝ3) = ∞. We prove new decomposition results for Besov spaces, which are key in the conception and existence theory of such solutions.
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Edin, Hans. "Partial Discharges Studied with Variable Frequency of the Applied Voltage." Doctoral thesis, KTH, Elektrotekniska system, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3207.
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This thesis concerns partial discharge (PD) diagnostics withvariable frequency of applied voltage in the frequency range 1mHz - 400 Hz. The exploration of a new type of spectroscopythat combines partial discharge analysis and dielectricresponse is demonstrated. A question addressed is if and howthe PD activity varies with the frequency of the appliedvoltage. The nature of an existing frequency dependence couldbe useful in the classification of different defects and tojudge the degree of progressive ageing. A Variable-Frequency Phase Resolved Partial DischargeAnalysis (VF-PRPDA) technique is developed for the appliedvoltage frequency range 1 mHz - 400 Hz. The VF-PRPDA techniqueis combined with a system for high voltage dielectricspectroscopy that allows simultaneous measurements. TheVF-PRPDA technique is used for studying the frequencydependence of PD. The PD activity is for example measured byintegrated measures like total charge per cycle and totalnumber of discharges per cycle. Statistical measures like mean,standard deviation, skewness, kurtosis etc. are applied tomeasure the frequency dependence of the phasedistributions. High voltage dielectric spectroscopy is supplemented withharmonic analysis for studying non-linear dielectric responsecurrents. The VF-PRPDA technique is demonstrated on defined objectslike point-plane gaps and artificial voids, but also on aninsulated stator bar and a paper insulated cable. Surfacedischarges on insulating surfaces are studied in an environmentwith a controlled relative humidity and temperature. Theadsorption of moisture on the insulating surface alters thesurface conductivity of the surface and the frequencydependence of the PD activity. The influence of temperature upon the PD activity is studiedfor a oil paper insulated cable. The results of the measurements show that the partialdischarge activity in general is frequency dependent over thefrequency range 1 mHz - 400 Hz. The reasons behind thefrequency dependence are linked to surface- and bulk-conducting mechanisms, frequency dependent field distributionsand statistical effects of the supply of start electrons. An algorithm is developed that relates the phase resolved PDcurrent measured with the PRPDA technique to the non-linearcurrent measured with dielectric spectroscopy. The algorithm isexperimentally verified by simultaneous measurements of PRPDAand dielectric spectroscopy on defined objects. The resultsexplain the contribution of PD to the apparent capacitance andloss. Moreover, the harmonics of the fundamental currentcomponent yield information about, for example, polaritydependent discharge sources. Keywords:diagnostic methods, partial discharges, phaseresolved, variable frequency, dielectric spectroscopy,dielectric response, harmonics, insulationQC 20100527
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Gibson, Andrew Robert. "Harnessing the non-linear coupling of odd harmonics for control of charged particle dynamics in radio-frequency plasmas." Thesis, Queen's University Belfast, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680121.
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Over the past number of years multiple frequency capacitively coupled plasmas have achieved widespread usage in plasma based nano-fabrication. However,the control of charged particle dynamics in such discharges is often limited by poor understanding of the non-linear coupling between the frequencies used. This is particularly true for plasmas produced in molecular gases. such as oxygen. where long-lived reactive neutral species can significantly affect the dynamics of charged particles. As these gases are used frequently in industry. it is crucial to achieve better understanding of their characteristics under multiple frequency excitation. In order to understand the dynamics of non-linear frequency coupling. this work proposes a novel dual frequency excitation scheme utilizing odd harmonics. The odd harmonic approach has been studied systematically utilizing both numerical simulations and experiments in plasmas produced in molecular oxygen gas. Through these Investigations it has been demonstrated that the frequencies used and the ratio to which they contribute to the resultant voltage waveform have significant influence over the final plasma parameters. This occurs through electron heating and ionization mode transitions which are non~linearly dependent upon the frequency contributions to the overall voltage waveform. A specific scheme for controlling the ion bombardment energy and ion flux to the substrate in Industrial plasma applications. using frequencies of 13.56 MHz and 40.68 MHz has been proposed. It has been predicted. through numerical simulations. and confirmed through experimental measurements. that the proposed scheme offers enhanced control of plasma properties over a wide parameter range. Furthermore. a critical benchmark study has been performed by undertaking a quantitative comparison between the results of state-of-the-art numerical simulations and experimental data. This has identified areas where further improvement in the understanding and modelling of oxygen plasmas is required in order to utilize numerical simulations in a truly quantitative manner for process design and control.
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Gorman, Timothy Thomas. "Attosecond Probing of Electron Dynamics in Atoms and Molecules using Tunable Mid-Infrared Drivers." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu15428283538078.
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Hopper, Christopher Peter. "On the regularity of holonomically constrained minimisers in the calculus of variations." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d8bde7a2-7dae-44d2-919d-48b9f2543789.
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This thesis concerns the regularity of holonomic minimisers of variational integrals in the context of direct methods in the calculus of variations. Specifically, we consider Sobolev mappings from a bounded domain into a connected compact Riemannian manifold without boundary, to which such mappings are said to be holonomically constrained. For a general class of strictly quasiconvex integral functionals, we give a direct proof of local C1,α-Hölder continuity, for some 0 < α < 1, of holonomic minimisers off a relatively closed 'singular set' of Lebesgue measure zero. Crucially, the proof constructs comparison maps using the universal covering of the target manifold, the lifting of Sobolev mappings to the covering space and the connectedness of the covering space. A certain tangential A-harmonic approximation lemma obtained directly using a Lipschitz approximation argument is also given. In the context of holonomic minimisers of regular variational integrals, we also provide bounds on the Hausdorff dimension of the singular set by generalising a variational difference quotient method to the holonomically constrained case with critical growth. The results are analogous to energy-minimising harmonic maps into compact manifolds, however in this case the proof does not use a monotonicity formula. We discuss several applications to variational problems in condensed matter physics, in particular those concerning the superfluidity of liquid helium-3 and nematic liquid crystals. In these problems, the class of mappings are constrained to an orbit of 'broken symmetries' or 'manifold of internal states', which correspond to a sub-group of residual symmetries.
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Harper, Sharleen Anne. "Mathematical models for dispersal of aerosol droplets in an agricultural setting : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Mathematics at Massey University, Albany, New Zealand." Massey University, 2008. http://hdl.handle.net/10179/814.
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Agrichemical spray drift is an issue of concern for the orcharding industry. Shelterbelts surrounding orchard blocks can significantly reduce spray drift by intercepting droplets from the airflow. At present, there is little information available with which to predict drift deposits downwind, particularly in the case of a fully-sheltered orchard block. In this thesis, we develop a simple mathematical model for the transport of airborne drifting spray droplets, including the effects of droplet evaporation and interception by a shelterbelt. The object is for the model to capture the major features of the droplet transport, yet be simple enough to determine an analytic solution, so that the deposit on the ground may be easily calculated and the effect of parameter variations observed. We model the droplet transport using an advection-dispersion equation, with a trapping term added to represent the shelterbelt. In order to proceed analytically, we discretise the shelterbelt by dividing it into a three-dimensional array of blocks, with the trapping in each block concentrated to the point at its centre. First, we consider the more straightforward case where the droplets do not evaporate; solutions are presented in one, two and three dimensions, along with explicit expressions for the total amount trapped and the deposit on the ground. With evaporation, the model is more difficult to solve analytically, and the solutions obtained are nestled in integral equations which are evaluated numerically. In both cases, examples are presented to show the deposition profile on the ground downwind of the shelterbelt, and the corresponding reduction in deposit from the same scenario without the shelterbelt.
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Eslick, John. "A Dynamical Study of the Evolution of Pressure Waves Propagating through a Semi-Infinite Region of Homogeneous Gas Combustion Subject to a Time-Harmonic Signal at the Boundary." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/1367.
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In this dissertation, the evolution of a pressure wave driven by a harmonic signal on the boundary during gas combustion is studied. The problem is modeled by a nonlinear, hyperbolic partial differential equation. Steady-state behavior is investigated using the perturbation method to ensure that enough time has passed for any transient effects to have dissipated. The zeroth, first and second-order perturbation solutions are obtained and their moduli are plotted against frequency. It is seen that the first and second-order corrections have unique maxima that shift to the right as the frequency decreases and to the left as the frequency increases. Dispersion relations are determined and their limiting behavior investigated in the low and high frequency regimes. It is seen that for low frequencies, the medium assumes a diffusive-like nature. However, for high frequencies the medium behaves similarly to one exhibiting relaxation. The phase speed is determined and its limiting behavior examined. For low frequencies, the phase speed is approximately equal to sqrt[ω/(n+1)] and for high frequencies, it behaves as 1/(n+1), where n is the mode number. Additionally, a maximum allowable value of the perturbation parameter, ε = 0.8, is determined that ensures boundedness of the solution. The location of the peak of the first-order correction, xmax, as a function of frequency is determined and is seen to approach the limiting value of 0.828/sqrt(ω) as the frequency tends to zero and the constant value of 2 ln 2 as the frequency tends to infinity. Analytic expressions are obtained for the approximate general perturbation solution in the low and high-frequency regimes and are plotted together with the perturbation solution in the corresponding frequency regimes, where the agreement is seen to be excellent. Finally, the solution obtained from the perturbation method is compared with the long-time solution obtained by the finite-difference scheme; again, ensuring that the transient effects have dissipated. Since the finite-difference scheme requires a right boundary, its location is chosen so that the wave dissipates in amplitude enough so that any reflections from the boundary will be negligible. The perturbation solution and the finite-difference solution are found to be in excellent agreement. Thus, the validity of the perturbation method is established.
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Frost, david L. Mr, and Frank Hagelberg. "Isotropic Oscillator Under a Magnetic and Spatially Varying Electric Field." Digital Commons @ East Tennessee State University, 2014. https://dc.etsu.edu/honors/415.
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We investigate the energy levels of a particle confined in the isotropic oscillator potential with a magnetic and spatially varying electric field. Here we are able to exactly solve the Schrodinger equation, using matrix methods, for the first excited states. To this end we find that the spatial gradient of the electric field acts as a magnetic field in certain circumstances. Here we present the changes in the energy levels as functions of the electric field, and other parameters.
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Wheeler, Jonathan Allen. "The Scaling of High Harmonics with Mid-Infrared Driving Fields and a Method for the Spatial Isolation of Individual Subfemtosecond Pulses." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1339165013.
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McGuire, John Andrew. "Femtosecond nonlinear spectroscopy at surfaces Second-harmonic probing of hole burning at the Si(111)7x7 surface and fourier-transform sum-frequency vibrational spectroscopy." Berkeley, Calif. : Oak Ridge, Tenn. : Lawrence Berkeley National Laboratory ; distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy, 2004. http://www.osti.gov/servlets/purl/836810-xRj01W/native/.
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Thesis (Ph.D.); Submitted to the University of California, Berkeley, CA (US); 24 Nov 2004.Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--56751" McGuire, John Andrew. USDOE Director. Office of Science. Office of Basic Energy Sciences. Materials Science and Engineering Division (US) 11/24/2004. Report is also available in paper and microfiche from NTIS.
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Le, Blanc Mario 1960. "Un trait fondamental de l'écriture harmonique de Franz Schubert : la division symétrique de l'octave en trois parties." Thesis, McGill University, 1985. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65952.
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DIAS, ARTUR F. "Metodo PsubN para calculos de blindagem em geometria de multiplacas." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10771.
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Made available in DSpace on 2014-10-09T12:43:49Z (GMT). No. of bitstreams: 0Made available in DSpace on 2014-10-09T14:10:01Z (GMT). No. of bitstreams: 1 06779.pdf: 6662459 bytes, checksum: 5a5ae589785a8bad523a922f578319f8 (MD5)
Tese (Doutoramento)
IPEN/T
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Iwai, Akinori. "Linear and Nonlinear Functions of Plasmas in Electromagnetic Metamaterials." Kyoto University, 2019. http://hdl.handle.net/2433/242471.
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Rocha, Kelvin Raymond. "A variational approach for viewpoint-based visibility maximization." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24816.
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Thesis (Ph.D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2008.Committee Chair: Allen R. Tannenbaum; Committee Member: Anthony J. Yezzi; Committee Member: Gregory Turk; Committee Member: Joel R. Jackson; Committee Member: Patricio A. Vela
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Burtea, Cosmin. "Méthodes d'analyse de Fourier en hydrodynamique : des mascarets aux fluides avec capillarité." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1047/document.
Full textAbstract:
Dans la première partie de cette thèse on étudie les systèmes abcd qui ont été dérivés par J.L. Bona, M. Chen et J.-C. Saut en 2002. Ces systèmes sont des modèles approximant le problème d'ondes hydrodynamiques dans le régime de Boussinesq, à savoir, des vagues de faible amplitude et de grande longueur d'onde. Dans les deux premiers chapitres on considère le problème d'existence en temps long à savoir la construction de solutions pour les systèmes abcd qui ont leur temps d'existence minoré par $1/varepsilon$ où $varepsilon$ est le rapport entre une amplitude typique du vague et la profondeur du canal. Dans un premier temps on considère des données initiales appartenant aux espaces de Sobolev qui sont inclus dans l'espace des fonctions continues qui s'annulent à l'infini. D'un point de vue physique cette situatuion correspond à des vagues sont localisées en espace. Le point clé est la construction d'une fonctionnelle non linéaire d'énergie qui contrôle certaines normes de Sobolev sur un intervalle de temps long. Pour y arriver, on travaille avec des équations localisées en fréquence. Cette approche nous permet d'obtenir des résultats d'existence en temps long en demandant moins de régularité sur les données initiales. Un deuxième avantage de notre méthode est que l'on peut traiter d'une manière unifiée presque tous les cas correspondant aux différentes valeurs des paramètres abcd. Dans le deuxième chapitre on montre des résultats d'existence en temps long pour le cas des données ayant un comportement non trivial à l'infini.Ce type des données est relevant pour l'étude de la propagation des mascarets. L'idée qui est à la base de ces résultats est de considérer un découpage convenable de la donnée initiale en hautes et basses fréquences. Dans le troisième chapitre on emploie des schémas de volumes finis afin de construire des solutions numériques. On utilise ensuite nos schémas pour étudier l'interaction d'ondes progressives.La deuxième partie de ce manuscrit est consacrée à l'étude des problèmes de régularité optimale pour le système de Navier-Stokes qui régi l'évolution d'un fluide incompressible, inhomogène et pour le système Navier-Stokes-Korteweg utilisé pour prendre en compte les effets de capillarité. Plus précisément, on montre que ces systèmes sont bien-posés dans leurs espaces critiques, à savoir, les espaces quiont la même invariance par changement d'échelle que les systèmes eux-mêmes. Pour pouvoir démontrer ce type de résultats on a besoin d'établir de nouvelles estimations pour un problème de type Stokes avec des coefficients variablesThe first part of the present thesis deals with the so -called abcd systems which were derived by J.L. Bona, M. Chen and J.-C. Saut back in 2002. These systems are approximation models for the waterwaves problem in the Boussinesq regime, that is, waves of small amplitude and long wavelength. In the first two chapters we address the long time existence problem which consists in constructing solutions for the Cauchy problem associated to the abcd systems and prove that the maximal time of existence is bounded from below by some physically relevant quantity. First, we consider the case of initial data belonging to some Sobolev spaces imbedded in the space of continuous functions which vanish at infinity. Physically, this corresponds to spatially localized waves. The key ingredient is to construct a nonlinear energy functional which controls appropriate Sobolev norms on the desired time scales. This is accomplished by working with spectrally localized equations. The two important features of our method is that we require lower regularity levels in order to develop a long time existence theory and we may treat in an uni ed manner most of the cases corresponding to the di erent values of the parameters. In the second chapter, we prove the long time existence results for the case of data thatdoes not necessarily vanish at in nity. This is especially useful if one has in mind bore propagation. One of the key ideas of the proof is to consider a well-adapted high-low frequency decomposition of the initial data. In the third chapter, we propose infinite volume schemes in order to construct numerical solutions. We use these schemes in order to study traveling waves interaction.The second part of this manuscript, is devoted to the study of optimal regularity issues for the incompressible inhomogeneous Navier-Stokes system and the Navier-Stokes-Korteweg system used in order to take in account capillarity effects. More precisely, we prove that these systems are well-posed in their truly critical spaces i.e. the spaces that have the same scale invariance as the system itself. Inorder to achieve this we derive new estimates for a Stoke-like problem with time independent variable coefficients
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Wen, Dan. "Estudo hidrodinâmico de correlações de partículas e fluxo coletivo em colisões de íons pesados relativísticos /." Guaratinguetá, 2019. http://hdl.handle.net/11449/190962.
Full textAbstract:
Orientador: Wei-Liang QianResumo: O sucesso da descrição hidrodinâmica das colisões de íons pesados relativísticos desempenha um papel vital para entender as propriedades da matéria QCD. A essência da evolução hidrodinâmica, em geral, foi atribuída à resposta dinâmica às condições iniciais flutuantes. Em particular, as características observadas nas correlações de duas partículas, referidas como ``cume'' e ``ombro'', mostraram ser reproduzidas com sucesso por simulações hidrodinâmicas com condições iniciais flutuantes evento a evento, mas não por condições iniciais médias. Posteriormente, leva ao entendimento atual, através de extensos estudos de análise hidrodinâmica/transporte baseada em eventos por eventos, que as correlações de duas partículas para o momento transversal inferior podem ser interpretadas principalmente em termos de harmônicos de fluxo $ v_n $. Notavelmente, o fluxo triangular, $ v_3 $, é atribuído principalmente à aparência da estrutura do ``ombro'' no lado externo da partícula acionadora. Além disso, entende-se que esses coeficientes harmônicos estão intimamente associados aos correspondentes $ \varepsilon_n $, as anisotropias da distribuição inicial de energia. No entanto, a linearidade entre $ v_n $ e $ \varepsilon_n $ se torna menos evidente para harmônicos maiores que $ n = 2 $. Isso sugere que as próprias flutuações de evento a evento carregam informações importantes, além da linearidade observada. Se alguém se restringe apenas à análise das relações/correlações médias de eventos entr... (Resumo completo, clicar acesso eletrônico abaixo)
Doutor
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Mailman, Matthew. "An Interpretive Approach to Two Wind Partitas of Franz Vincent Krommer: Partita in F, Op. 57 (1808) and Partita in E-flat, Op. 79 (1810), A Lecture Recital : Together with Three Recitals of Selected Works of Stravinsky, Hanson, Martin Mailman, Holst and Walton." Thesis, University of North Texas, 1995. https://digital.library.unt.edu/ark:/67531/metadc277888/.
Full textAbstract:
An interpretive approach to performing two works by Franz Krommer for wind ensemble. Including a short history of Harmoniemusik, with origins, development, and chronology of the instruments and repertoire, the roles of "better-known" composers of Harmoniemusik, and its importance in both general music history and history of the wind band. An account of known biographical detail concerning Franz Krommer, his life, his musical involvement and career in Europe, and his place in music history. An overview of his compositions for wind groups other than the Harmoniemusik, including his symphonic music and concertos. Detailed analyses of the two octet-partitas, Partita in F, Op. 57 and Partita in E-flat, Op. 79, with discussion of thematic, harmonic, melodic, articulation, and formal characteristics illustrated through score examples. Examination of issues for a conductor to consider when approaching a performance of these works such as instrumentation (modern vs. period instruments, selecting 16-foot instrument), taking (or not taking) repeats with respect to form, interpreting articulations, determining metronomic tempos, ensemble balance, and style based on wind music of the Classical period. Also, how this music can (and why it should) be used by wind conductors as both a teaching supplement and a compositional model for pieces from the Classical period. Conclusion includes a call for further research on Krommer and his works.
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Šedý, Michal. "Syntéza struktur s elektromagnetickým zádržným pásmem." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-218036.
Full textAbstract:
In microwave frequency band, the planar technology is mainly used to fabricate electronic circuits. Propagation of surface waves belongs to the significant problem of this technology. Surface waves can cause unwanted coupling among particular parts of the structure and can degrade its parameters. The problem can be solved using an electromagnetic band gap structure (EBG). These periodic structures are able to suppress surface waves in different frequency bands. This thesis is focused on the modeling of these structures in the program COMSOL Multiphysics.
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Daniel, Priscillia. "Etude des propriétés électriques de câbles isolés au polyéthylène réticulé en présence de cavités gazeuses et vieillis sous tensions DC ou DC avec harmoniques." Thesis, Université Grenoble Alpes (ComUE), 2019. http://www.theses.fr/2019GREAT114.
Full textAbstract:
Dans le but de favoriser l’intégration des énergies renouvelables, les réseaux de transport sous haute tension continue (HVDC) sont privilégiés. L’interface entre les réseaux AC et DC est assurée par des convertisseurs de puissance qui génèrent des harmoniques. Il est établi que, lors de la réticulation du polyéthylène (PER – XLPE), des microcavités apparaissent dans la matrice du polymère. L’objectif de la thèse est donc d’examiner l’impact éventuel des harmoniques en présence de microcavités. Suivant leur taille et les conditions de champ électrique, les microcavités piégées dans le XLPE peuvent être le siège de décharges partielles (DP). Deux types de câbles différents ont été vieillis : un câble moyenne tension AC (MVAC) comprenant des défauts de tailles millimétriques provoqués artificiellement et un minicâble avec un grade de XLPE pour HVDC. Les tronçons de câbles MVAC ont été soumis à des contraintes en tension DC sous des températures de 90 à 120°C. Les minicâbles ont subi des contraintes en tensions superposées DC+AC à 1800 Hz et à des températures de 70 et 90°C. Ces vieillissements ont été caractérisés par des mesures de DP, de courant et de spectroscopie diélectrique. En présence de cavités millimétriques, les vieillissements ont provoqué une baisse de la tension d’apparition des DP (TADP) et une augmentation de l’amplitude des DP. Pour les minicâbles, les valeurs TADP mesurées ont été attribuées, selon le modèle proposé, à des cavités de l’ordre de 10 µm de diamètre. Les courants de conduction ont augmenté et le seuil d’apparition des charges d’espace diminué en fonction des vieillissements subis. Enfin, les caractérisations de spectroscopie diélectrique ont montré des différences de la réponse spectrale entre des vieillissements thermiques et électrothermiques. Une simulation numérique a permis d’estimer les renforcements de champ électrique sous tension DC dans des cavités sphériques et délaminations. Ces facteurs sont plus élevés que ceux utilisés sous tension AC. L’implication des charges d’espace dans les phénomènes de DP dans les cavités est discutée sur la base de ces mesures et simulationsIn order to accommodate large scale renewable energy, electrical networks integrates more and more high-voltage direct current (HVDC) systems. Interface between AC and DC networks is ensured by power converters which also generate harmonics. It is known that during crosslinking process of polyethylene (XLPE), microcavities appear inside polymer matrix. This study aims to examine possible impact of these harmonics in presence of microcavities. Depending on their size and on the electrical field, partial discharges (PD) can occur in these microcavities. Two types of cables have been aged: a medium voltage AC (MVAC) cable with millimetric cavities induced artificially and a model cable with an HVDC XLPE grade. MVAC cable sections have been submitted to DC voltage under temperatures between 90 to 120°C. Model cables have been subjected to superimposed DC plus 1800 Hz AC voltages under temperatures from 70 to 90°C. Ageing have been characterized by PD, current and dielectric spectroscopy measurements. In presence of millimetric cavities, ageing have caused a decrease in PD inception voltage (PDIV) and an increase in PD magnitude. For model cable, PDIV values have been assigned, according to a proposed model, to cavities of about 10 µm in diameter. Conduction currents were increased and space charges threshold field decreased depending on ageing. Finally, dielectric spectroscopy characterisations have shown differences between thermal and electrothermal ageing. Electrical field enhancement factors under DC voltage have been estimated in various cavity geometries thanks to numerical simulations. These factors reveal to be higher than the ones used under AC voltage. Space charges involvement in PD phenomena inside cavities is discussed based on measurements and simulations
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Deguillard, Estelle. "Simulations de Dynamique Particulaire Dissipative pour le calcul de tension interfaciale dans des systèmes eau/tensioactif/huile." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112288/document.
Full textAbstract:
La tension interfaciale est une grandeur physico-chimique d'intérêt pour de nombreuses industries et notamment l'industrie pétrolière. Cette grandeur est l'un des paramètres qui permet d'optimiser le rendement d'un puits de pétrole. La difficulté liée à sa mesure dans les conditions réservoirs a amené à étudier les systèmes eau/tensioactif/huile par simulation moléculaire. Ce travail a permis de montrer que la Dynamique Particulaire Dissipative (DPD) était un outil adapté pour l’étude de systèmes eau/tensioactif/huile sous différents aspects, de la caractérisation de la structure des interfaces au calcul de la tension interfaciale. Cette thèse a permis la démonstration de l’influence non-négligeable de la variation des paramètres de la force harmonique, l’amplitude K et la distance d’équilibre r0 , sur le calcul de la tension interfaciale et sur la structure des interfaces à forte concentration en tensioactif. En effet, la structure des tensioactifs aux interfaces est le résultat d’une balance subtile entre les forces intra et inter moléculaire. L’étude d’une population modèle de tensioactifs non chargés a permis de montrer que la DPD reproduit bien l'évolution de la tension interfaciale en fonction de la concentration en tensioactif en solution et en fonction du coefficient de partage de tensioactifs modèles non chargés. Une méthodologie est proposée pour caractériser les systèmes contenant des interfaces et où la tension interfaciale est calculée.Des travaux prospectifs ont permis de montrer que la DPD permettait d'étudier des phénomènes liés à la tension interfaciale comme le mûrissement d'Ostwald dans les émulsions d'huile dans l'eau. Ces derniers travaux ouvrent la voie à l’étude d’autres systèmes d’intérêt pour le milieu pétrolier comme le décollement de gouttes de pétroles adsorbées sur des parois ou l’étude d’émulsions pétrolièresThe interfacial tension is a physical-chemical property that numerous industrial areas have an interest of especially the petroleum industry. This property is one of the many which helps to optimize production wells' rate of return. Measuring that property in reservoir's conditions (high pressure and temperature) is highly difficult and led to study water/surfactant/oil systems using molecular modeling. The difficulty to measure that specific physical-chemical property linked to the pressure and temperature conditions in the reservoirs led the scientists to study water/surfactant/oil systems using molecular modeling. This thesis establishes that the Dissipative Particle Dynamics (DPD) is able to study water/surfactant/oil systems. The study of the effect of the variation of the harmonic force's parameters, namely the force constant K and the equilibrium distance r0, demonstrated that their variation can heavily influence the interfacial tension computation. Actually, a subtle balance exists between the intra and inter-molecular interactions, which influences the local structure of the surfactants at the oil-water interface, modifies the interfacial tension and influences the interface stability. It was demonstrated that DPD reproduces the variation of interfacial tension with the bulk surfactant concentration and the effect of the variation of hydrophobicity of models of un-charged surfactants on interfacial tension by mean of their coefficient partition. We established a method to properly study systems containing interfaces where interfacial tension is computed. Prospective work showed that DPD was a good tool to study microscopic phenomenon which can be observed macroscopically like the Ostwald ripening in oil in water emulsions. This is a first step before studying others systems of interest for the petroleum industry such as oil/water emulsion or the adsorption of oil droplets on rock wall
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Vest, Ambroise. "Stabilisation rapide et observation en plusieurs instants de systèmes oscillants." Phd thesis, Université de Strasbourg, 2013. http://tel.archives-ouvertes.fr/tel-00864407.
Full textAbstract:
Ce travail est constitué de deux parties indépendantes traitant chacune d'un problème issu de la théorie du contrôle des équations aux dérivées partielles. La première partie est consacrée à l'étude d'un feedback explicite et déjà connu, s'appliquant à des systèmes linéaires, réversibles en temps et éventuellement munis d'un opérateur de contrôle non-borné. On justifie le caractère bien posé du problème en boucle fermée via la théorie des semi-groupes puis on étudie le taux de décroissance des solutions du système régulé. La seconde partie concerne un problème d'observation pour la corde vibrante : on détermine comment choisir des instants d'observation pour que la position de la corde à ces instants permette de retrouver les conditions initiales tout en préservant une certaine régularité. La méthode, qui repose sur des résultats d'approximation diophantienne, est ensuite étendue à d'autres systèmes. En utilisant une méthode de dualité on démontre aussi un résultat de contrôlabilité exacte.
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Blaclard, Guillaume. "Ultra-High Intense Laser on Dense Plasmas : from Periodic to Chaotic Dynamics." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS133.
Full textAbstract:
L'émergence des lasers ultra-brefs et ultra-intenses a permis le développement d'une nouvelle branche de la physique encore largement inexplorée : la physique UHI (pour Ultra-High Intensity). Lors de la réflexion d'un tel laser sur une cible solide, l'intensité au foyer I₀ peut atteindre des valeurs aussi importantes que 10¹⁸⁻²⁰ W.cm⁻², suffisamment pour ioniser complétement la matière. Le plasma ainsi formé se détend sur une longueur caractéristique Lg, nommée longueur de gradient. Quand Lg <<λ₀ (longueur d'onde du laser), le plasma dense se comporte comme un miroir de qualité optique capable de réfléchir spéculairement la lumière incidente : c'est un miroir plasma. Ce système physique remarquable peut être utilisé dans de multiples applications principalement comme source compacte de faisceaux de particules à hautes charges et hautes énergies ou de lumière intense, principalement ultraviolet ou X, grâce à un phénomène de génération d'harmoniques d'ordres élevés. Le bon contrôle de ces sources nécessite de clairement identifier les différents mécanismes de couplage entre lumière et matière en jeu lors de l'interaction. Dans ce manuscrit, cela est rendu possible grâce à de précises simulations de type Particle-In-Cell (PIC) réalisées avec le code WARP+PXR. Ce nouveau code emploie un solveur pseudo-spectral pour résoudre les équations de Maxwell. Celui-ci améliore grandement la précision des simulations et notamment des émissions harmoniques et électroniques, que les solveurs plus standards ne parviennent à décrire, même à hautes résolutions. Grâce à des simulations WARP+PXR, nous avons étudié l'influence de Lg sur les observables expérimentales que sont les émissions de lumière et de particules, quand un laser de puissance (I₀ = 10¹⁹ W.cm⁻²) se réfléchit sur un plasma dense. Notre étude révèle une claire transition entre un mécanisme périodique en temps et un processus chaotique quand l'interface devient plus lisse. Nous nous sommes principalement concentrés sur le deuxième mécanisme, appelé chauffage stochastique pour lequel des études en profondeur vont être menées en fonction de différents paramètres d'interaction. Dans ce régime, les électrons de la partie sous-dense du plasma subissent une dynamique chaotique dans l'onde stationnaire formée par la superposition des ondes incidente et réfléchie, ce qui leur permet d'absorber une importante part de l'énergie laser. La nature fondamentale de la dynamique en jeu est révélée grâce aux équations du mouvement au sein des deux ondes que l'on peut réduire en équations de pendules forcés (comme celui de Kapitza), systèmes bien connus comme chaotiques. Cette correspondance apporte une intuition physique profonde sur le comportement des électrons pour différentes configurations laser. Ceci nous permet in fine de prédire les principaux aspects du chauffage stochastiqueThe advent of high power femtosecond lasers has paved the way to a promising and still largely unexplored branch of physics called Ultra-High Intensity physics (UHI). Once such a laser is focused on a solid target, the laser intensity I₀ can reach values as large as 10¹⁸⁻²⁰ W.cm⁻², for which matter is fully ionized. The plasma thus formed expands towards vacuum on a spatial scale characterized by a quantity Lg called the density gradient scale length. When Lg << λ₀ (laser wavelength), the dense plasma therefore acts as an optical mirror that specularly reflects the incident light: it is a plasma mirror. This remarkable physical system can be used in many scientific applications as compact source of high-energy and high-charge particle beams (electrons, ions) or bright source of radiations ranging from extreme ultraviolet-rays to X-rays through high harmonic generation processes. In order to finely control these sources, it is required to properly identify the different coupling mechanisms between light and matter at play during the interaction. In this manuscript, this has been made possible by performing accurate Particle-In-Cell (PIC) simulations with the WARP+PXR code. This recently developed code advances Maxwell’s equations in Fourier space, which proves to correctly model harmonic/electron emissions that standard codes fail to accurate describe even at high resolution. Based on WARP+PXR PIC simulations, we investigate the influence of Lg on the experimentally observed emission of light and particles, when a high-power laser pulse (I₀ = 10¹⁹ W.cm⁻²) reflects off a dense plasma. Our study reveals an unambiguous transition from a temporally periodic mechanism to a chaotic process as the interface becomes smoother. In particular, the latter mechanism, named stochastic heating, is fully characterized as well as its domain of validity in terms of laser-plasma parameters. In this regime, electrons in the underdense part of the gradient are exposed to the standing wave formed in front of the overcritical part of the plasma by superposition of incidence and reflected beams. While evolving in the two waves, electrons behave chaotically and absorb an important fraction of the laser energy. The nature of the interaction is revealed by reducing the equations of motion of particles in two waves to physical systems, such Kapitza’s pendulum, well-known to exhibit chaos. That correspondence gives deep physical intuitions on how electrons behave in different laser configurations, which allows us to predict major features of stochastic heating
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Erdal, Ferhat. "Ultimate Load Capacity Of Optimally Designed Cellular Beams." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613007/index.pdf.
Full textAbstract:
Cellular beams became increasingly popular as an efficient structural form in
steel construction since their introduction. Their sophisticated design and
profiling process provides greater flexibility in beam proportioning for
strength, depth, size and location of circular holes. The purpose of
manufacturing these beams is to increase overall beam depth, the moment of
inertia and section modulus, which results in greater strength and rigidity.
Cellular beams are used as primary or secondary floor beams in order to
achieve long spans and service integration. They are also used as roof beams
beyond the range of portal-frame construction, and are the perfect solution for
curved roof applications, combining weight savings with a low-cost
manufacturing process.
The purpose of the current research is to study optimum design, ultimate load
capacity under applied load and finite element analysis of non-composite
cellular beams. The first part of the research program focuses on the optimum
design of steel cellular beams using one of the stochastic search methods called
&ldquoharmony search algorithm&rdquo
. The minimum weight is taken as the design objective while the design constraints are implemented from the Steel Construction Institute. Design constraints include the displacement limitations, overall beam flexural capacity, beam shear capacity, overall beam buckling strength, web post flexure and buckling, vierendeel bending of upper and lower tees and local buckling of compression flange. The design methods adopted in this publication are consistent with BS5950. In the second part of the research, which is the experimental work, twelve non-composite cellular beams are tested to determine the ultimate load carrying capacities of these beams under using a hydraulic plug to apply point load. The tested cellular beam specimens have been designed by using harmony search algorithm. Finally, finite element analysis program is used to perform elastic buckling analysis and predict critical loads of all steel cellular beams. Finite element analysis results are then compared with experimental test results for each tested cellular beam.
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Theeten, Marc. "Semi-microscopic and microscopic three-body models of nuclei and hypernuclei." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210268.
Full textAbstract:
De nombreux noyaux atomiques et hypernoyaux se modélisent comme des structures à trois corps. C'est le cas, par exemple, de noyaux à halo, comme 6He, ou de noyaux stables, comme 12C et 9Be. En effet, 6He se caractérise comme un système à trois corps, formé d'un coeur (une particule alpha) et de deux neutrons de valence faiblement liés. Le noyau de 12C peut s'étudier comme un système lié formé de trois particules alphas, tandis que 9Be peut être décrit comme la liaison de deux particules alphas et d'un neutron.
Dans les exemples précédents, les particules alphas sont des amas de nucléons. Elles possèdent donc une structure interne dont il faut tenir compte en raison du principe de Pauli.
Les modèles les plus réalistes pour décrire les structures à trois corps sont les modèles "microscopiques". Ces modèles prennent en compte explicitement tous les nucléons et respectent exactement le principe d'antisymétrisation de Pauli. Cependant, l'application de ces modèles est fortement limitée en pratique, car ils exigent de trop nombreux et trop longs calculs.
Par conséquent, pour simplifier considérablement les calculs et permettre l'étude des structures à trois corps, des modèles moins détaillés, de type "semi-microscopiques", sont également développés. Dans ces modèles, on représente les amas de nucléons comme de simples particules ponctuelles. Dans ce cas, la modélisation consiste à construire les potentiels effectifs entre les amas, puis à les employer dans les modèles à trois corps.
Dans ce travail, nous avons développé les modèles "semi-microscopiques à trois corps". Les potentiels effectifs entre amas sont directement déduits des forces entre nucléons (selon la RGM à 2 corps). Ces potentiels sont "non-locaux", et dépendent des énergies des amas qui interagissent. Ils permettent de simuler le principe de Pauli et les échanges de nucléons entre les amas. La dépendance en l'énergie se révèle être un inconvénient dans les modèles à trois corps. Les potentiels effectifs sont par conséquent transformés en de nouveaux potentiels (non-locaux) indépendants de l'énergie, bien adaptés aux modèles à trois corps. Les modèles "semi-microscopiques" sont beaucoup plus simples et plus rapides que les modèles "microscopiques". Ils fournissent les fonctions d'onde des états liés à trois corps des noyaux légers et hypernoyaux. Cela permet d'une part de comprendre les propriétés spectroscopiques nucléaires, et d'autre part, cela ouvre la voie pour de futurs modèles de réactions nucléaires impliquant les structures à trois corps.
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Several atomic nuclei and hypernuclei can be modelled as three-body structures: e.g. two-neutron halo nuclei, such as 6He, and other nuclei, such as 12C and 9Be.
Indeed 6He can be represented as a three-body system, made up of a core (an alpha particle) and two weakly bound valence neutrons. The 12C nucleus can be studied as a bound system formed by three alpha particles, while the 9Be nucleus can be described as the binding of two alpha particles and one neutron.
In these typical examples, the alpha particles are clusters of nucleons. They have an internal structure that must be taken into account because of the Pauli principle.
The most realistic models are the "microscopic models". In these models, all the nucleons are taken into account, and the Pauli antisymmetrisation principle is fully respected. However, the application of the "microscopic models" is limited in practice, because they require too many laborious calculations.
Therefore, in order to greatly simplify the calculations, "semi-microscopic models" are developed. In those models, the clusters of nucleons are treated as ("structureless") pointlike particles. The models then consist in determining the effective potentials between the clusters, and in using them in three-body models.
In the present work, we have developed "semi-microscopic models". The effective potentials between the clusters are directly obtained from the interactions between nucleons (according to the two-cluster RGM). These potentials are "nonlocal", and depend on the energy of the interacting clusters. The non-locality is a direct consequence of the Pauli principle and the exchanges of nucleons between the clusters. The energy-dependence of the potentials turns out to be a drawback in three-body models. Therefore, the effective potentials are transformed into energy-independent potentials, which can be used in three-body models. The "semi-microscopic models" are much simpler and faster than the "microscopic models". They provide the three-body bound-state wave functions (i.e. the spectroscopic properties and the structure) of light nuclei and hypernuclei. Such wave functions are also the basic ingredient that will be used in future reactions models.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
37
Ge, Yuxin. "Sur quelques équations aux dérivées partielles nonlinéaires provenant de la géométrie." Cachan, Ecole normale supérieure, 1997. http://www.theses.fr/1997DENS0029.
Full textAbstract:
Les résultats présentés dans cette thèse concernent l'existence de solutions de certaines équations aux dérivées partielles elliptiques issues de la géométrie. Nous montrons l'existence des surfaces à courbure moyenne constante et des applications harmoniques entre variétés à l'aide de la théorie de morse sur les variétés hilbertiennes. Nous construisons aussi des surfaces immergées à courbure de gauss prescrite.
38
Carter, Mark Dwain. "Nonlinear wave-particle interactions at cyclotron harmonic frequencies." 1985. http://catalog.hathitrust.org/api/volumes/oclc/13442289.html.
Full textAbstract:
Thesis (Ph. D.)--University of Wisconsin--Madison, 1985.Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 112-115).
39
Huang, Kuo-Chen, and 黃國真. "Optimization Design of Power Harmonic Filters Using Particle Swarm Algorithm." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/89721139808726952812.
Full textAbstract:
碩士淡江大學
電機工程學系碩士在職專班
94
This thesis uses Particle Swarm Algorithm to design a passive filter in order to find the turning point and the capacitor value enabling the generated electric harmonics within the limit set by Taiwan Power Company and to improve the harmonic problems of low voltage electric system. Nowadays, many fields take the concept of simulating biological wisdom for doing researches on most optimization problems, and Particle Swarm Optimization is one of the latest technologies. Particle Swarm Optimization is resulted from the observation of birds’ food-seeking behaviors; that is, each bird gets his food by his self-experiences and interactions among the group. Every particle having its own solution to the questions goes through self- recognition and group guide up to the best solution. In addition, this thesis considers the budget of construction and the improvement of power factors to meet the goal of low budget and high efficiency. Finally, for a system of low voltage distribution system, comparison of the results of the proposed method with those of the other method shows that the proposed method indeed suppresses the effects of harmonics better than the other method.
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Ginsberg, Jared Scott. "Symmetry Breaking and Harmonic Generation in Metasurfaces and 2-Dimensional Materials." Thesis, 2021. https://doi.org/10.7916/d8-3k1x-6z87.
Full textAbstract:
A strong argument can be made that physics is, at its core, the study of symmetries. Nonlinear optics is certainly no exception, with an enormous number of distinct processes each depending in its own way on the underlying symmetries of the physical system, the light, or of nature itself. Restricting ourselves to optical harmonic generation, we will explore three unique physical systems as well as three symmetries. In each case, the controlled breaking of that symmetry will lead to optical enhancements, novel nonlinearities, or deep physical insights.
Beginning with silicon metasurfaces, we will explore the effects of even and odd spatial symmetries in optical systems. The periodic breaking of this symmetry will lead us to the highly engineerable physics of bound states in the continuum. By studying the harmonic emission from an atomic gas in the volume surrounding the metasurface, we will come to understand that significant nonlinear optical enhancements can be engineered with any linewidth and at any wavelength.
In the context of the two-dimensional material hexagonal boron nitride, we will investigate and break crystal inversion symmetries. Using an intense laser tuned to the phonon resonance of hexagonal boron nitride, large amplitude anharmonic ionic motions will provide us a powerful degree of control over the internal symmetries of the system at an atomic level. Breaking this symmetry, we measure short-lived even-order nonlinearities that would otherwise be forbidden in equilibrium. Our observations for second- and third- harmonic generation are confirmed by time-dependent density functional theory. Those simulations further extend the understanding of this symmetry-breaking effect to even higher order processes.
Lastly, single-crystal graphene and graphite provide an ideal platform through which to explore time-reversal symmetry. Chiral photons, or optical beams with ellipticity and handedness, are well known to break time-reversal symmetry. While applying high-power, chiral light to graphene, the breaking of time-reversal lifts a degeneracy of the K and K’ valleys in the momentum space Brillouin zone. Lifting this degeneracy, we unveil underlying spatial symmetry properties of graphene in odd-order third- and fifth- harmonic generation which should otherwise be unobservable. We also show experimentally, for the first time, that valley polarization and population can be extracted using our technique.
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Carley, Holly Kathleen. "The strong-coupling limit for the ground state of a particle harmonic oscillator interaction /." 2004. http://wwwlib.umi.com/dissertations/fullcit/3144627.
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Mentrup, Detlef. "Isothermal quantum dynamics: Investigations for the harmonic oscillator." Doctoral thesis, 2003. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2003052613.
Full textAbstract:
Thermostated time evolutions are on a firm ground and widely used in classical molecular dynamics (MD) simulations. Hamilton´s equations of motion are supplemented by time-dependent pseudofriction terms that convert the microcanonical isoenergetic time evolution into a canonical isothermal time evolution, thus permitting the calculation of canonical ensemble averages by time averaging. However, similar methods for quantum MD schemes are still lacking. Given the rich dynamical behavior of ultracold trapped quantum gases depending on the value of the s-wave scattering length, it is timely to investigate how classical thermostating methods can be combined with powerful approximate quantum dynamics schemes to deal with interacting quantum systems at finite temperature. In this work, the popular method of Nose and Hoover to create canonically distributed positions and momenta in classical MD simulations is generalized to a genuine quantum system of infinite dimensionality. We show that for the quantum harmonic oscillator, the equations of motion in terms of coherent states may be modified in a Nose-Hoover manner to mimic the coupling of the system to a thermal bath and create a quantum canonical ensemble. The method is developed initially for a single particle and then generalized to the case of an arbitrary number of identical quantum particles, involving entangled distribution functions. The resulting isothermal equations of motion for bosons and fermions contain additional terms leading to Bose-attraction and Pauli-blocking, respectively. Questions of ergodicity are discussed for different coupling schemes. In the many-particle case, the superiority of the Nose-Hoover technique to a Langevin approach is demonstrated. In addition, the work contains an investigation of the Grilli-Tosatti thermostating method applied to the harmonic oscillator, and calculations for quantum wavefunctions moving with a time-invariant shape in a harmonic potential.
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Sitar, Scott. "Entire Solutions to Dirichlet Type Problems." Thesis, 2007. http://hdl.handle.net/10012/3147.
Full textAbstract:
In this thesis, we examined some Dirichlet type problems of
the form:
\begin{eqnarray*}
\triangle u & = & 0\ {\rm in\ } \mathbb{R}^n \\
u & = & f\ {\rm on\ } \psi = 0,
\end{eqnarray*}
and we were particularly interested in finding entire solutions
when entire data was prescribed. This is an extension of the work
of D. Siegel, M. Mouratidis, and M. Chamberland, who were interested
in finding polynomial solutions when polynomial data was prescribed.
In the cases where they found that polynomial solutions always existed
for any polynomial data, we tried to show that entire
solutions always existed given any entire data. For half space
problems we were successful, but when we compared this to the heat
equation, we found that we needed to impose restrictions on the type
of data allowed. For problems where data is prescribed on a pair of
intersecting lines in the plane, we found a surprising dependence
between the existence of an entire solution and the number
theoretic properties of the angle between the lines. We were
able to show that for numbers $\alpha$ with $\omega_1$ finite
according to Mahler's classification of transcendental numbers,
there will always be an entire solution given
entire data for the angle $2\alpha\pi$ between the lines.
We were also able to construct an uncountable, dense set of
angles of measure 0, much in the spirit of Liouville's number,
for which there will not always be an entire solution for all
entire data.
Finally, we investigated a problem where data is given
on the boundary of an infinite strip in the plane. We were unable to settle
this problem, but we were able to reduce it to other
{\it a priori} more tractable problems.
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Mombourquette, Ethan. "On Holder continuity of weak solutions to degenerate linear elliptic partial differential equations." 2013. http://hdl.handle.net/10222/35442.
Full textAbstract:
For degenerate elliptic partial differential equations, it is often desirable to show that a weak solution is smooth. The first and most difficult step in this process is establishing local Hölder continuity. Sufficient conditions for establishing continuity have already been documented in [FP], [SW1], and [MRW], and their necessity in [R]. However, the complexity of the equations discussed in those works makes it difficult to understand the core structure of the arguments employed. Here, we present a harmonic-analytic method for establishing Hölder continuity of weak solutions in context of a simple linear equation
div(Q?u) = f
in a homogeneous space structure in order to showcase the form of the argument. Ad- ditionally, we correct an oversight in the adaptation of the John-Nirenberg inequality presented in [SW1], restricting it to a much smaller class of balls.
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Bielen, Andrew Scott. "Spherical harmonics solutions to second order forms of the Boltzmann transport equation using particle transport code sceptre." 2008. http://etda.libraries.psu.edu/theses/approved/WorldWideIndex/ETD-2713/index.html.
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Grobler, Jonathan. "Hypernuclear bound states with two /\-Particles." Diss., 2009. http://hdl.handle.net/10500/3222.
Full textAbstract:
The double hypernuclear systems are studied within the context of the
hyperspherical approach. Possible bound states of these systems are sought
as zeros of the corresponding three-body Jost function in the complex energy
plane. Hypercentral potentials for the system are constructed from known
potentials in order to determine bound states of the system. Calculated
binding energies for double- hypernuclei having A = 4 − 20, are presented.Physics
M.Sc. (Physics)
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"GaN HEMT Modeling and Design for Millimeter and Sub-millimeter Wave Power Amplifiers through Monte Carlo Particle-based Device Simulations." Doctoral diss., 2011. http://hdl.handle.net/2286/R.I.14440.
Full textAbstract:
abstract: The drive towards device scaling and large output power in millimeter and sub-millimeter wave power amplifiers results in a highly non-linear, out-of-equilibrium charge transport regime. Particle-based Full Band Monte Carlo device simulators allow an accurate description of this carrier dynamics at the nanoscale. This work initially compares GaN high electron mobility transistors (HEMTs) based on the established Ga-face technology and the emerging N-face technology, through a modeling approach that allows a fair comparison, indicating that the N-face devices exhibit improved performance with respect to Ga-face ones due to the natural back-barrier confinement that mitigates short-channel-effects. An investigation is then carried out on the minimum aspect ratio (i.e. gate length to gate-to-channel-distance ratio) that limits short channel effects in ultra-scaled GaN and InP HEMTs, indicating that this value in GaN devices is 15 while in InP devices is 7.5. This difference is believed to be related to the different dielectric properties of the two materials, and the corresponding different electric field distributions. The dielectric effects of the passivation layer in millimeter-wave, high-power GaN HEMTs are also investigated, finding that the effective gate length is increased by fringing capacitances, enhanced by the dielectrics in regions adjacent to the gate for layers thicker than 5 nm, strongly affecting the frequency performance of deep sub-micron devices. Lastly, efficient Full Band Monte Carlo particle-based device simulations of the large-signal performance of mm-wave transistor power amplifiers with high-Q matching networks are reported for the first time. In particular, a CellularMonte Carlo (CMC) code is self-consistently coupled with a Harmonic Balance (HB) frequency domain circuit solver. Due to the iterative nature of the HB algorithm, this simulation approach is possible only due to the computational efficiency of the CMC, which uses pre-computed scattering tables. On the other hand, HB allows the direct simulation of the steady-state behavior of circuits with long transient time. This work provides an accurate and efficient tool for the device early-stage design, which allows a computerbased performance evaluation in lieu of the extremely time-consuming and expensive iterations of prototyping and experimental large-signal characterization.Dissertation/Thesis
Ph.D. Electrical Engineering 2011
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Chien, Shih-Hai, and 錢世海. "A Study on Calculating the Optimal Turn-on Angle of Multilevel Cascade Inverter with Particle Swarm Optimization to Reduce Total Harmonic Distortion and the Verification of Hardware-in-the-loop." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/31463317801239457041.
Full textAbstract:
碩士國立聯合大學
電機工程學系碩士班
102
The optimal switch conduction angle to solve the cascade multilevel inverter is regarded as the research subject in this study. The voltage on the power switches of a cascade multilevel inverter could be applied to high-power environments. Nevertheless, it is necessary to use the modulation strategy to have the output waveform approach sine waves, where the harmonic optimization staircase waveform strategy in step modulation could reduce the switching frequency. However, nonlinear equations need to be solved for calculating the optimal switch conduction angle. A rapid solving algorithm is required for the real-time application. To rapidly solve the optimal switch conduction angle for the harmonic optimization staircase waveform of a cascade multilevel inverter, a modified particle swarm optimization, which combines standard particle swarm optimization and complementary particle swarm optimization, is proposed in this study, where the objective function applies the sum of squares of KKT prerequisite for satisfying the harmonic optimization. The optimization is implemented with MATLAB and FPGA hardware-in-the-loop, and Simulink is used for constructing the cascade multilevel inverter model for the simulation and analysis efficacy. Since total harmonic distortion calculation and square root calculation are avoided in the objective function and the particle velocity update is improved, the proposed method appear faster speed of convergence than standard particle swarm optimization does.
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Schulz, Jochen. "Field reconstructions and range tests for acoustics and electromagnetics in homogeneous and layered media." Doctoral thesis, 2007. http://hdl.handle.net/11858/00-1735-0000-0006-B3A5-B.
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