Tesi sul tema "Convergence order"
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Van, der Walt Jan Harm. "Order convergence on Archimedean vector lattices and applications". Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-02062006-130754.
Testo completoLiang, Jingwei. "Convergence rates of first-order operator splitting methods". Caen, 2016. http://www.theses.fr/2016CAEN2024.
Testo completoThis manuscript is concerned with convergence analysis of first-order operator splitting methods that are ubiquitous in modern non-smooth optimization. It consists of three main theoretical advances on this class of methods, namely global convergence rates, novel operator splitting schemes and local linear convergence. First, we propose global (sub-linear) and local (linear) convergence rates for the inexact \KM iteration built from non-expansive operators, and its application to a variety of monotone splitting schemes. Then we design two novel multi-step inertial operator splitting algorithms, both in the convex and non-convex settings, and establish their global convergence. Finally, building on the key concept of partial smoothness, we present a unified and sharp local linear convergence analysis for the class of first-order proximal splitting methods for optimization. We show that for all these algorithms, under appropriate non-degeneracy conditions, the iterates generated by each of these methods will (i) identify the involved partial smooth manifolds in finite time, and then (ii) will enter a local linear convergence regime. The linear convergence rates are characterized precisely based on the structure of the optimization problem, that of the proximal splitting scheme, and the geometry of the identified active manifolds. Our theoretical findings are systematically illustrated on applications arising from inverse problems, signal/image processing and machine learning
Wang, Yuan. "Convergence and Boundedness of Probability-One Homotopies for Model Order Reduction". Diss., Virginia Tech, 1997. http://hdl.handle.net/10919/30716.
Testo completoPh. D.
Davies, Peredur Glyn Cwyfan. "Identifying word-order convergence in the speech of Welsh-English bilinguals". Thesis, Bangor University, 2010. https://research.bangor.ac.uk/portal/en/theses/identifying-wordorder-convergence-in-the-speech-of-welshenglish-bilinguals(200be10a-4e1f-4b0f-ae56-f707bfce8556).html.
Testo completoCouchman, Benjamin Luke Streatfield. "On the convergence of higher-order finite element methods to weak solutions". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115685.
Testo completoCataloged from PDF version of thesis.
Includes bibliographical references (pages 77-79).
The ability to handle discontinuities appropriately is essential when solving nonlinear hyperbolic partial differential equations (PDEs). Discrete solutions to the PDE must converge to weak solutions in order for the discontinuity propagation speed to be correct. As shown by the Lax-Wendroff theorem, one method to guarantee that convergence, if it occurs, will be to a weak solution is to use a discretely conservative scheme. However, discrete conservation is not a strict requirement for convergence to a weak solution. This suggests a hierarchy of discretizations, where discretely conservative schemes are a subset of the larger class of methods that converge to the weak solution. We show here that a range of finite element methods converge to the weak solution without using discrete conservation arguments. The effect of using quadrature rules to approximate integrals is also considered. In addition, we show that solutions using non-conservation working variables also converge to weak solutions.
by Benjamin Luke Streatfield Couchman.
S.M.
Ghadimi, Euhanna. "Accelerating Convergence of Large-scale Optimization Algorithms". Doctoral thesis, KTH, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-162377.
Testo completoQC 20150327
Kim, Taejong. "Mesh independent convergence of modified inexact Newton methods for second order nonlinear problems". Texas A&M University, 2003. http://hdl.handle.net/1969.1/3870.
Testo completoButch, Nicholas Patrick. "The search for quantum criticality near the convergence of hidden order and ferromagnetism". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3307110.
Testo completoTitle from first page of PDF file (viewed July 3, 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 139-149).
Bürger, Steven, e Bernd Hofmann. "About a deficit in low order convergence rates on the example of autoconvolution". Universitätsbibliothek Chemnitz, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-130630.
Testo completoAgbebaku, Dennis Ferdinand. "Solution of conservation laws via convergence space completion". Diss., University of Pretoria, 2011. http://hdl.handle.net/2263/27791.
Testo completoDissertation (MSc)--University of Pretoria, 2011.
Mathematics and Applied Mathematics
Unrestricted
Hasse, Gunther Willy. "Convergence from chaos to order in capital projects using chaos attractors – an explorative study". Thesis, University of Pretoria, 2020. http://hdl.handle.net/2263/73060.
Testo completoThesis (PhD)--University of Pretoria, 2020.
Graduate School of Technology Management (GSTM)
PhD
Unrestricted
Khirirat, Sarit. "Randomized first-order methods for convex optimization : Improved convergence rate bounds and experimental evaluations". Thesis, KTH, Reglerteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214697.
Testo completoStorskaliga optimeringsproblem uppkommer i många moderna tillämpningar,från maskininlärning till distribuerad styrning. Traditionella optimeringsalgoritmerhar svårt att hantera dessa storskaliga beräkningar. Nyligen har ett antalrandomiserade gradient-baserade optimeringsmetoder föreslagits för optimeringöver stora datamängder, men det är i dagsläget inte känt hur man på bästasätt väljer algoritmparametrar för dem och vilka garantier man kan ge på deraskonvergensegenskaper.I detta examensarbete härleder vi konvergensresultat för era randomiseradegradient-baserade optimeringsalgoritmer, för konvexa och starkt konvexafunktioner samt med och utan konvexa bivillkor. Vi har implementerat dessaalgoritmer i MATLAB och utvärderat dem på klassificeringsproblem. Våra numeriskaexperiment validerar våra teoretiska resultat och visar hur skalning,normalisering och konditionering påverkar den praktiska prestandan hos randomiseradegradientmetoder.
Barré, Mathieu. "Worst-case analysis of efficient first-order methods". Electronic Thesis or Diss., Université Paris sciences et lettres, 2021. http://www.theses.fr/2021UPSLE064.
Testo completoMany modern applications rely on solving optimization problems (e.g., computational biology, mechanics, finance), establishing optimization methods as crucial tools in many scientific fields. Providing guarantees on the (hopefully good) behaviors of these methods is therefore of significant interest. A standard way of analyzing optimization algorithms consists in worst-case reasoning. That is, providing guarantees on the behavior of an algorithm (e.g. its convergence speed), that are independent of the function on which the algorithm is applied and true for every function in a particular class. This thesis aims at providing worst-case analyses of a few efficient first-order optimization methods. We start by the study of Anderson acceleration methods, for which we provide new explicit worst-case bounds guaranteeing precisely when acceleration occurs. We obtained these guarantees by providing upper bounds on a variation of the classical Chebyshev optimization problem on polynomials, that we believe of independent interest. Then, we extend the Performance Estimation Problem (PEP) framework, that was originally designed for principled analyses of fixed-step algorithms, to study first-order methods with adaptive parameters. This is illustrated in particular through the worst-case analyses of the canonical gradient method with Polyak step sizes that use gradient norms and function values information, and of an accelerated version of it. The approach is also presented on other standard adaptive algorithms. Finally, the last contribution of this thesis is to further develop the PEP methodology for analyzing first-order methods relying on inexact proximal computations. Using this framework, we produce algorithms with optimized worst-case guarantees and provide (numerical and analytical) worst-case bounds for some standard algorithms in the literature
Hao, Zhaopeng. "High-order numerical methods for integral fractional Laplacian: algorithm and analysis". Digital WPI, 2020. https://digitalcommons.wpi.edu/etd-dissertations/612.
Testo completoAmeismeier, Tobias [Verfasser], e Helmut [Akademischer Betreuer] Abels. "Thin Vibrating Rods: Γ-Convergence, Large Time Existence and First Order Asymptotics / Tobias Ameismeier ; Betreuer: Helmut Abels". Regensburg : Universitätsbibliothek Regensburg, 2021. http://d-nb.info/1236401433/34.
Testo completoNyamayaro, Takura T. A. "On the design and implementation of a hybrid numerical method for singularly perturbed two-point boundary value problems". University of the Western Cape, 2014. http://hdl.handle.net/11394/4326.
Testo completoWith the development of technology seen in the last few decades, numerous solvers have been developed to provide adequate solutions to the problems that model different aspects of science and engineering. Quite often, these solvers are tailor-made for specific classes of problems. Therefore, more of such must be developed to accompany the growing need for mathematical models that help in the understanding of the contemporary world. This thesis treats two point boundary value singularly perturbed problems. The solution to this type of problem undergoes steep changes in narrow regions (called boundary or internal layer regions) thus rendering the classical numerical procedures inappropriate. To this end, robust numerical methods such as finite difference methods, in particular fitted mesh and fitted operator methods have extensively been used. While the former consists of transforming the continuous problem into a discrete one on a non-uniform mesh, the latter involves a special discretisation of the problem on a uniform mesh and are known to be more accurate. Both classes of methods are suitably designed to accommodate the rapid change(s) in the solution. Quite often, finite difference methods on piece-wise uniform meshes (of Shishkin-type) are adopted. However, methods based on such non-uniform meshes, though layer-resolving, are not easily extendable to higher dimensions. This work aims at investigating the possibility of capitalising on the advantages of both fitted mesh and fitted operator methods. Theoretical results are confirmed by extensive numerical simulations.
Zhao, Qingrong. "Reduced-Order Robust Adaptive Controller Design and Convergence Analysis for Uncertain SISO Linear Systems with Noisy Output Measurements". University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1194564628.
Testo completoBRITO, MARGARIDA. "Encadrement presque sur des statistiques d'ordre". Paris 6, 1987. http://www.theses.fr/1987PA066284.
Testo completoMunyakazi, Justin Bazimaziki. "Higher Order Numerical Methods for Singular Perturbation Problems". Thesis, Online Access, 2009. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_6335_1277251056.pdf.
Testo completoValois, Isabela da Silva. "PATHS OF CONVERGENCE OF AGRICULTURAL INCOME IN BRAZIL - AN ANALYSIS FROM MARKOV PROCESS OF FIRST ORDER FOR THE PERIOD 1996 TO 2009". Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8110.
Testo completoThe Brazilian agricultural sector has made in the period of stabilization after the Real Plan (1996-2009) a satisfactory economic dynamics, in which the level of agricultural products began an upward trend and virtually uninterrupted growth. This performance suggests that state economies are undergoing a process of catching up, which in the long run there would be a tendency for poorer economies achieve the same level of economic growth (in terms of per capita agricultural GDP) of the richest economies, setting a process of convergence to steady state. Accordingly, this paper seeks to analyze the convergence of per capita agricultural income between the states of Brazil, making sure that the dynamics of the agricultural sector had contributed to the reduction of inequalities existing interstate. To this end, it was used the first-order Markov process. The results indicate the occurrence of movements backward economies to levels of income per capita agricultural lower, indicating that the economies under review showed a trend of impoverishment, despite the global economic growth presented by the sector over the period. Among the factors that led these economies to tread a path of impoverishment, one can cite the emphasis of public policy to export crops, not covered by all the federating units of the country, which would result in the strengthening of the state economies have developed, expense of which are under development; beyond the migration of manpower for the agricultural production centers in more developed agricultural, causing the "Red Queen Effect," in which the growth of agricultural GDP does not translate into growth of income per capita in the field. However, the focus of this study is to identify the occurrence of convergence / divergence, no inferences about the causes that led to the initiation of such a movement, since these factors make room for new studies that seek to investigate them, in order to provide tools for the formulation of agricultural policies aimed at minimizing or even reversal of the causes that lead to poverty in the countryside.
O setor agropecuÃrio brasileiro tem apresentado no perÃodo de pÃs estabilizaÃÃo do Plano Real (1996-2009) uma dinÃmica econÃmica satisfatÃria, em que o nÃvel de produto agropecuÃrio iniciou uma trajetÃria ascendente e praticamente ininterrupta de crescimento. Tal performance sugere que as economias estaduais estejam passando por um processo de catching up, em que no longo prazo existiria uma tendÃncia das economias mais pobres alcanÃarem o mesmo nÃvel de crescimento econÃmico (em termos de PIB per capita agropecuÃrio) das economias mais ricas, configurando um processo de convergÃncia no steady state. Eom efeito, este, trabalho busca analisar a convergÃncia da renda agropecuÃria per capita entre os estados do Brasil, verificando se a dinÃmica do setor agrÃcola teria contribuÃdo para a reduÃÃo das desigualdades interestaduais preexistentes. Para tal, fez-se uso do processo markoviano de primeira ordem. Os resultados apontaram a ocorrÃncia de movimentos de retrocesso das economias para nÃveis de renda per capita agropecuÃria inferiores, indicando que as economias em anÃlise apresentaram uma tendÃncia de empobrecimento, apesar do crescimento econÃmico global do setor ao longo do perÃodo. Dentre os fatores que levariam tais economias a trilharem uma trajetÃria de empobrecimento, pode-se citar a Ãnfase das polÃticas pÃblicas Ãs culturas de exportaÃÃo, nÃo contempladas por todas as unidades federativas do PaÃs, o que resultaria no fortalecimento das economias estaduais jà desenvolvidas, em detrimento das que se encontram em desenvolvimento; alÃm dos movimentos migratÃrios da mÃo-de-obra agropecuÃria para os centros produtores agrÃcolas mais desenvolvidos, causando o âEfeito Rainha Vermelhaâ, em que o crescimento do PIB agropecuÃrio nÃo se traduziria em crescimento das rendas per capita no campo. Contudo, o foco deste estudo consiste na identificaÃÃo da ocorrÃncia do processo de convergÃncia/divergÃncia, sem inferir sobre as causas que levariam ao desencadeamento de tal movimento, jà que tais fatores abrem espaÃo para novos estudos que busquem investigÃ-los, a fim de poder fornecer instrumentos de formulaÃÃo de polÃticas pÃblicas agropecuÃrias direcionadas à minimizaÃÃo ou mesmo reversÃo das causas que levam à pobreza no campo.
Riffaud, Sébastien. "Modèles réduits : convergence entre calcul et données pour la mécanique des fluides". Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0334.
Testo completoThe objective of this thesis is to significantly reduce the computational cost associated with numerical simulations governed by partial differential equations. For this purpose, we consider reduced-order models (ROMs), which typically consist of a training stage, in which high-fidelity solutions are collected to define a low-dimensional trial subspace, and a prediction stage, where this data-driven trial subspace is then exploited to achieve fast or real-time simulations. The first contribution of this thesis concerns the modeling of gas flows in both hydrodynamic and rarefied regimes. In this work, we develop a new reduced-order approximation of the Boltzmann-BGK equation, based on Proper Orthogonal Decomposition (POD) in the training stage and on the Galerkin method in the prediction stage. We investigate the simulation of unsteady flows containing shock waves, boundary layers and vortices in 1D and 2D. The results demonstrate the stability, accuracy and significant computational speedup factor delivered by the ROM with respect to the high-fidelity model. The second topic of this thesis deals with the optimal transport problem and its applications to model order reduction. In particular, we propose to use the optimal transport theory in order to analyze and enrich the training database containing the high-fidelity solution snapshots. Reproduction and prediction of unsteady flows, governed by the 1D Boltzmann-BGK equation, show the improvement of the accuracy and reliability of the ROM resulting from these two applications. Finally, the last contribution of this thesis concerns the development of a domain decomposition method based on the Discontinuous Galerkin method. In this approach, the ROM approximates the solution where a significant dimensionality reduction can be achieved while the high-fidelity model is employed elsewhere. The Discontinuous Galerkin method for the ROM offers a simple way to recover the global solution by linking local solutions through numerical fluxes at cell interfaces. The proposed method is evaluated for parametric problems governed by the quasi-1D and 2D Euler equations. The results demonstrate the accuracy of the proposed method and the significant reduction of the computational cost with respect to the high-fidelity model
Sanja, Lončar. "Negative Selection - An Absolute Measure of Arbitrary Algorithmic Order Execution". Phd thesis, Univerzitet u Novom Sadu, Prirodno-matematički fakultet u Novom Sadu, 2017. https://www.cris.uns.ac.rs/record.jsf?recordId=104861&source=NDLTD&language=en.
Testo completoAlgoritamsko trgovanje je automatizovani proces izvršavanja naloga na elektronskim berzama. Može se primeniti na širok spektar nansijskih instrumenata kojima se trguje na berzi i karakteriše ga značajna kontrola investitora nad izvršavanjem njegovih naloga, pri čemu se teži nalaženju pravog balansa izmedu troška i rizika u vezi sa izvršenjem naloga. S ozirom da se merenjem performasi izvršenja naloga određuje da li je postignuto najbolje izvršenje, u praksi postoji značajan broj različitih pokazatelja. Najčešće su to pokazatelji cena, neki od njih se određuju pre trgovanja (eng. Pre-trade), neki u toku trgovanja (eng. Intraday), a neki nakon trgovanja (eng. Post-trade). Dva najdominantnija pokazatelja cena su VWAP i Arrival Price koji je zajedno sa ostalim "pre-trade" pokazateljima cena poznat kao Implementation shortfall (IS).Pojam negative selekcije se uvodi kao "post-trade" mera performansi algoritama izvršenja, polazeći od pojma optimalnog naloga, koji predstavlja idealni nalog koji se mogao izvrsiti u datom vremenskom intervalu, pri ćemu se pod pojmom "idealni" podrazumeva nalog kojim se postiže najbolja cena u tržišnim uslovima koji su vladali u toku tog vremenskog intervala. Negativna selekcija se definiše kao razlika vektora optimalnog i izvršenog naloga, pri čemu su vektori naloga defisani kao količine akcija na odgovarajućim pozicijama cena knjige naloga. Ona je jednaka nuli kada je nalog optimalno izvršen; negativna, ako nalog nije (u potpunosti) izvršen, a pozitivna ako je nalog izvršen, ali po nepovoljnoj ceni.Uvođenje mere negativne selekcije zasnovano je na ideji da se ponudi nova, alternativna, mera performansi i da se u odnosu na nju nađe optimalna trajektorija i konstruiše optimalno izvršenje naloga.U prvom poglavlju teze dati su lista notacija kao i pregled definicija i teorema neophodnih za izlaganje materije. Poglavlja 2 i 3 bave se teorijskim pregledom pojmova i literature u vezi sa mikrostrukturom tržišta, pokazateljima trgovanja i algoritamskim trgovanjem. Originalni rezultati su predstavljeni u 4. i 5. poglavlju. Poglavlje 4 sadrži konstrukciju optimalnog naloga, definiciju i osobine negativne selekcije. Teorijski i praktični rezultati u vezi sa osobinama negativna selekcije dati su u [35]. Poglavlje 5 sadrži teorijske osnove stohastičke optimizacije, definiciju modela za optimalno izvršenje, kao i originalni rad u vezi sa metodom nemonotonog linijskog pretraživanja [31], dok 6. poglavlje sadrži empirijske rezultate.
Liu, Yating. "Optimal Quantization : Limit Theorem, Clustering and Simulation of the McKean-Vlasov Equation". Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS215.
Testo completoThis thesis contains two parts. The first part addresses two limit theorems related to optimal quantization. The first limit theorem is the characterization of the convergence in the Wasserstein distance of probability measures by the pointwise convergence of Lp-quantization error functions on Rd and on a separable Hilbert space. The second limit theorem is the convergence rate of the optimal quantizer and the clustering performance for a probability measure sequence (μn)n∈N∗ on Rd converging in the Wasserstein distance, especially when (μn)n∈N∗ are the empirical measures with finite second moment but possibly unbounded support. The second part of this manuscript is devoted to the approximation and the simulation of the McKean-Vlasov equation, including several quantization based schemes and a hybrid particle-quantization scheme. We first give a proof of the existence and uniqueness of a strong solution of the McKean- Vlasov equation dXt = b(t, Xt, μt)dt + σ(t, Xt, μt)dBt under the Lipschitz coefficient condition by using Feyel’s method (see Bouleau (1988)[Section 7]). Then, we establish the convergence rate of the “theoretical” Euler scheme and as an application, we establish functional convex order results for scaled McKean-Vlasov equations with an affine drift. In the last chapter, we prove the convergence rate of the particle method, several quantization based schemes and the hybrid scheme. Finally, we simulate two examples: the Burger’s equation (Bossy and Talay (1997)) in one dimensional setting and the Network of FitzHugh-Nagumo neurons (Baladron et al. (2012)) in dimension 3
Dejan, Ćebić. "Optimalni višekoračni metodi NJutnovog tipa za nalaženje višestrukih korena nelinearne jednačine sa poznatom celobrojnom višestrukošću". Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2018. https://www.cris.uns.ac.rs/record.jsf?recordId=105555&source=NDLTD&language=en.
Testo completoThis thesis deals with the problem of determing multiple roots of real nonlinear equations where the multiplicity is some integer known in advance. The convergence order and optimal properties of some well-known methods such as Liu-Zhou method and Zhou-Chen-Song method are theoretically analyzed and numerically tested. The dependence of optimal convergence order on multiplicity has been derived and explained. Further, two new efficient families of methods with optimal eighth convergence order have been constructed. Furthermore, some new families of two-step methods are considered to solve certain problems where the classical Newton-type methods fail.
Tain, Cyril. "Modelling of type II superconductors : implementation with FreeFEM". Electronic Thesis or Diss., Normandie, 2023. http://www.theses.fr/2023NORMIR40.
Testo completoIn this thesis we present four models for type II superconductors: the London model, the time dependent Ginzburg-Landau (TDGL) model, the steady state Ginzburg-Landau model and an Abelian-Higgs model. For the London model a problem with cylindrical symmetry was considered. A hydrodynamic formulation of the problem was established through the introduction of a stream function. Well-posedness of the problem was proved. The external magnetic field was computed for 2D and 3D domains. In 3D a boundary element method was implemented using a recent feature of FreeFem. For the TDGL model two codes based on two variational formulations were proposed and tested on classical benchmarks of the literature in 2D and 3D. In the steady state GL model a Sobolev gradient technique was used to find the equilibrium state. The results were compared with the ones given by the TDGL model. In the Abelian-Higgs model a 1D finite differences code written in Fortran was developed and tested with the construction of a manufactured system. The model was used to retrieve some of the properties of magnetization of superconductors
Davis, Clayton Paul. "Understanding and Improving Moment Method Scattering Solutions". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd620.pdf.
Testo completoVergnaud, Alban. "Améliorations de la précision et de la modélisation de la tension de surface au sein de la méthode SPH, et simulations de cas d'amerrissage d'urgence d'helicoptères". Thesis, Ecole centrale de Nantes, 2020. http://www.theses.fr/2020ECDN0033.
Testo completoSmoothed Particle Hydrodynamics (SPH) is a Lagrangian and meshless numerical method, used in many branches of physics and engineering (astrophysics, solid mechanics, fluid mechanics, etc...). In fluid mechanics, this method is now used in many application fields (naval engineering, automotive engineering, aeronautic engineering, etc...), using its meshless and Lagrangian features to simulate free surface flows with complex shapes and with many interface reconnexions. However, the SPH method still suffers from a lack of precision due to its Lagrangian feature and the relative complexity of the SPH operators. The objective of this thesis is to propose several improvements to increase the precision of the SPH method. The first part of this work focuses on a particle shifting technique aiming at breaking the Lagrangian structures inherently observed in SPH and which usually leads to a deterioration of the simulations. In particular, thanks to a theoretical study on consistency and convergence properties, a new shifting law is proposed. Secondly, a new viscous operator for near-body areas is proposed, based on a surface formulation of the boundary conditions. The third part concerns higher orders of convergence in the SPH method, and in particular for the case of Riemann-SPH schemes. A new reconstruction method, based the WENO scheme (Weighted Essentially Non-Oscillatory) and MLS (Moving Least Squares) interpolations, is proposed for the left and right state reconstructions of the Riemann problems. Then, a new accurate and robust surface tension model for single-phase flows is proposed, allowing namely to impose the contact angles at the contact line. Finally, as part of the SARAH project (increased SAfety and Robust certification for ditching of Aircraft and Helicopters ; European Unions Horizon 2020 Research and Innovation Programme Grant No. 724139), the last topic of this thesis is dedicated to the establishment of a numerical model allowing the SPH simulations of emergency ditching cases of helicopters. This model is validated thanks to comparisons with experimental results conducted in the wave basin of Ecole Centrale Nantes
Durochat, Clément. "Méthode de type Galerkin discontinu en maillages multi-éléments (et non-conformes) pour la résolution numérique des équations de Maxwell instationnaires". Thesis, Nice, 2013. http://www.theses.fr/2013NICE4005.
Testo completoThis thesis is concerned with the study of a Discontinuous Galerkin Time-Domain method (DGTD), for the numerical resolution of the unsteady Maxwell equations on hybrid tetrahedral/hexahedral in 3D (triangular/quadrangular in 2D) and non-conforming meshes, denoted by DGTD-PpQk method. Like in several studies on various hybrid time domain methods (such as a combination of Finite Volume with Finite Difference methods, or Finite Element with Finite Difference, etc.), our general objective is to mesh objects with complex geometry by tetrahedra for high precision and mesh the surrounding space by square elements for simplicity and speed. In the discretization scheme of the DGTD method considered here, the electromagnetic field components are approximated by a high order nodal polynomial, using a centered approximation for the surface integrals. Time integration of the associated semi-discrete equations is achieved by a second or fourth order Leap-Frog scheme. After introducing the historical and physical context of Maxwell equations, we present the details of the DGTD-PpQk method. We prove the L2 stability of this method by establishing the conservation of a discrete analog of the electromagnetic energy and a sufficient CFL-like stability condition is exhibited. The theoritical convergence of the scheme is also studied, this leads to a-priori error estimate that takes into account the hybrid nature of the mesh. Afterward, we perform a complete numerical study in 2D (TMz waves), for several test problems, on hybrid and non-conforming meshes, and for homogeneous or heterogeneous media. We do the same for the 3D implementation, with more realistic simulations, for example the propagation in a heterogeneous human head model. We show the consistency between the mathematical and numerical results of this DGTD-PpQk method, and its contribution in terms of accuracy and CPU time
Kulkarni, Shashank D. "Development and validation of a Method of Moments approach for modeling planar antenna structures". Worcester, Mass. : Worcester Polytechnic Institute, 2007. http://www.wpi.edu/Pubs/ETD/Available/etd-042007-151741/.
Testo completoKeywords: patch antennas; volume integral equation (VIE); method of moments (MoM); low order basis functions; convergence. Includes bibliographical references (leaves 169-186 ).
Sayi, Mbani T. "High Accuracy Fitted Operator Methods for Solving Interior Layer Problems". University of the Western Cape, 2020. http://hdl.handle.net/11394/7320.
Testo completoFitted operator finite difference methods (FOFDMs) for singularly perturbed problems have been explored for the last three decades. The construction of these numerical schemes is based on introducing a fitting factor along with the diffusion coefficient or by using principles of the non-standard finite difference methods. The FOFDMs based on the latter idea, are easy to construct and they are extendible to solve partial differential equations (PDEs) and their systems. Noting this flexible feature of the FOFDMs, this thesis deals with extension of these methods to solve interior layer problems, something that was still outstanding. The idea is then extended to solve singularly perturbed time-dependent PDEs whose solutions possess interior layers. The second aspect of this work is to improve accuracy of these approximation methods via methods like Richardson extrapolation. Having met these three objectives, we then extended our approach to solve singularly perturbed two-point boundary value problems with variable diffusion coefficients and analogous time-dependent PDEs. Careful analyses followed by extensive numerical simulations supporting theoretical findings are presented where necessary.
Miller, Kenyon Russell. "Convergent neural algorithms for pattern matching using high-order relational descriptions". Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/8219.
Testo completoSaunders, Martin. "Measurement of low-order structure factors by Convergent Beam Electron Diffraction". Thesis, University of Bath, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.359247.
Testo completoKouao, Serge Guy. "Incidence des facteurs institutionnels dans l’évolution de la structure financière des entreprises : cas d’entreprises françaises cotées à la bourse de Paris". Thesis, Bordeaux 4, 2011. http://www.theses.fr/2011BOR40032/document.
Testo completoBased on the pecking order and trade-off theories, this research aims to test empirically the relationship between corporate capital structure and institution. Both concepts share common characteristics fostering their conceptual association through the target debt ratio specifically via corporate behavior of financial conservatism. This opens new possibilities for analysis of that relationship, in particular, by mobilizing the new institutionalism framework. A sample of 204 French companies listed on the Paris stock exchange, with complete data between 1999 and 2007, was used to undertake the empirical part of the study. The main results indicate that all the traditional determinants of capital structure, except the size, play an important role in the financing policy of these companies. The level of corruption and the French stock market liquidity (legal and financial institutional variables) do not influence the choice of debt level, but rather play a significant role in the choice of debt maturity. In addition, the financial structure of these companies converges slowly but surely toward its target level
Sciannandrone, Daniele. "Acceleration and higher order schemes of a characteristic solver for the solution of the neutron transport equation in 3D axial geometries". Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112171/document.
Testo completoThe topic of our research is the application of the Method of Long Characteristics (MOC) to solve the Neutron Transport Equation in three-dimensional axial geometries. The strength of the MOC is in its precision and versatility. As a drawback, it requires a large amount of computational resources. This problem is even more severe in three-dimensional geometries, for which unknowns reach the order of tens of billions for assembly-level calculations.The first part of the research has dealt with the development of optimized tracking and reconstruction techniques which take advantage of the regularities of three-dimensional axial geometries. These methods have allowed a strong reduction of the memory requirements and a reduction of the execution time of the MOC calculation.The convergence of the iterative scheme has been accelerated with a lower-order transport operator (DPN) which is used for the initialization of the solution and for solving the synthetic problem during MOC iterations.The algorithms for the construction and solution of the MOC and DPN operators have been accelerated by using shared-memory parallel paradigms which are more suitable for standard desktop working stations. An important part of this research has been devoted to the implementation of scheduling techniques to improve the parallel efficiency.The convergence of the angular quadrature formula for three-dimensional cases is also studied. Some of these formulas take advantage of the reduced computational costs of the treatment of planar directions and the vertical direction to speed up the algorithm.The verification of the MOC solver has been done by comparing results with continuous-in-energy Monte Carlo calculations. For this purpose a coupling of the 3D MOC solver with the Subgroup method is proposed to take into account the effects of cross sections resonances. The full calculation of a FBR assembly requires about 2 hours of execution time with differences of few PCM with respect to the reference results.We also propose a higher order scheme of the MOC solver based on an axial polynomial expansion of the unknown within each mesh. This method allows the reduction of the meshes (and unknowns) by keeping the same precision.All the methods developed in this thesis have been implemented in the APOLLO3 version of the neutron transport solver TDT
Hejazi, Hala Ahmad. "Finite volume methods for simulating anomalous transport". Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/81751/1/Hala%20Ahmad_Hejazi_Thesis.pdf.
Testo completoBernoussi, Benaissa. "Compacité et ordre convergence dans les espace des fonctions mesurables et de mesures". Perpignan, 1990. http://www.theses.fr/1990PERP0087.
Testo completoKratz, Marie. "Some contributions in probability and statistics of extremes". Habilitation à diriger des recherches, Université Panthéon-Sorbonne - Paris I, 2005. http://tel.archives-ouvertes.fr/tel-00239329.
Testo completoThiel, Alena. "Heterotemporal convergences : travelling significations of order and their adaptations in the claims-making strategies of Accra's Makola market traders". Thesis, University of Aberdeen, 2015. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=228600.
Testo completoSato, Fernando Massami. "Numerical experiments with stable versions of the Generalized Finite Element Method". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/18/18134/tde-16102017-101710/.
Testo completoO Método dos Elementos Finitos Generalizados (MEFG) é essencialmente baseado no método da partição da unidade, que explora o conceito de partição da unidade para compatibilizar um conjunto de funções escolhidas para localmente aproximar de forma eficiente a solução. Apesar de suas vantagens bem conhecidas, o método pode apresentar algumas desvantagens. Por exemplo, o aumento do espaço de aproximação por meio das funções de enriquecimento pode introduzir dependências lineares no sistema de equações resolvente, assim como o aparecimento de elementos de mistura. Para contornar as desvantagens apontadas acima, algumas versões aprimoradas do MEFG foram desenvolvidas. O MEFG Estável é uma primeira versão aqui considerada na qual as funções de enriquecimento do MEFG são modificadas. O MEFG Estável de ordem superior propõe uma modificação adicional para a geração das funções de forma atreladas ao espaço enriquecido. Esta pesquisa visa apresentar e testar numericamente essas novas versões do MEFG recentemente propostas. Além de destacar suas principais características, alguns aspectos sobre a integração numérica quando usado o MEFG Estável de ordem superior, em particular, são também abordados. Por exemplo, detalha-se uma regra de divisão da área do elemento quadrilateral, guiada pela própria definição de sua partição da unidade. Os exemplos escolhidos para os experimentos numéricos consistem em chapas com geometrias favoráveis para explorar as vantagens de cada método. Essencialmente, examinam-se funções singulares com boas propriedades de aproximar a solução nas vizinhanças de vértices de cantos, bem como funções polinomiais para aproximar soluções suaves. Ademais, uma comparação entre o MEF convencional e os métodos aqui descritos é feita levando-se em consideração o número de condição do sistema escalonado e as razões de convergência do erro relativo em deslocamento. Finalmente, os experimentos numéricos mostram que o MEFG Estável de ordem superior é a mais robusta e confiável entre as versões do MEFG testadas.
Paditz, Ludwig. "Über mittlere Abweichungen". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-112977.
Testo completoIn this paper we study necessary and sufficient conditions for the validity of limit theorems on moderate deviations. Usually x-zones for moderate deviations are called in the terminilogy by YU.V.LINNIK (1971) "very narrow" zones of integral normal attraction. Moreover we analyse the remainder term appearing in the asymptotic relations. Informations on the order of the rate of convergence are given. Earlier results by several authors are generalized. Finally some references are given
Bérard, Bergery Blandine. "Approximation du temps local et intégration par régularisation". Thesis, Nancy 1, 2007. http://www.theses.fr/2007NAN10058/document.
Testo completoThe setting of this work is the integration by regularization of Russo and Vallois. The first part studies schemes of approximation of the local time of continuous semimartingales. If X is a reversible diffusion, the convergence of a first schema of approximation to the local time of X is proven, in probability uniformly on the compact sets. From this first schema, two other schemas of approximation for the local time are found. One converges in the semi-martingale case, the other in the Brownian case. Moreover, in the Brownian case, we estimate the rate of convergence in L^2(Omega) and a result of almost sure convergence is proven. The second part study the forward integral and the generalized quadratic variation, which have been defined by convergence of families of integrals, in probability uniformly on the compacts sets. In the case of Hölder processes, the almost sure convergence is proven. Finally, the second order convergence is studied in many cases
Manou-Abi, Solym Mawaki. "Théorèmes limites et ordres stochastiques relatifs aux lois et processus stables". Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30025/document.
Testo completoThis PhD Thesis is composed of three independent parts about stable laws and processes. In the first part, we establish convergence theorems (invariance principle) to stable processes, for additive functionals of a discrete time Markov chain that are not assumed to be square-integrable. The method is based on the use of mixing coefficients for Markov chains. In the second part, we obtain some rates of convergence to stable laws in the generalized central limit theorem by means of the Zolotarev ideal probability metric. The last part of the thesis is devoted to the study of convex ordering or convex comparison inequalities between stochastic integrals driven by stable processes. The main idea of our results is based on the forward-backward stochastic calculus for the stable case
Champier, Sylvie. "Convergence de schémas numériques type Volumes finis pour la résolution d'équations hyperboliques". Saint-Etienne, 1992. http://www.theses.fr/1992STET4007.
Testo completoJeschke, Anja [Verfasser], e Jörn [Akademischer Betreuer] Behrens. "Second Order Convergent Discontinuous Galerkin Projection Method for Dispersive Shallow Water Flows / Anja Jeschke ; Betreuer: Jörn Behrens". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1172880662/34.
Testo completoJeschke, Anja Verfasser], e Jörn [Akademischer Betreuer] [Behrens. "Second Order Convergent Discontinuous Galerkin Projection Method for Dispersive Shallow Water Flows / Anja Jeschke ; Betreuer: Jörn Behrens". Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://nbn-resolving.de/urn:nbn:de:gbv:18-94463.
Testo completoMartucci, Francesco. "L' ordre économique et monétaire de la Communauté européenne". Paris 1, 2007. http://www.theses.fr/2007PA010310.
Testo completoDebroux, Noémie. "Mathematical modelling of image processing problems : theoretical studies and applications to joint registration and segmentation". Thesis, Normandie, 2018. http://www.theses.fr/2018NORMIR02/document.
Testo completoIn this thesis, we study and jointly address several important image processing problems including registration that aims at aligning images through a deformation, image segmentation whose goal consists in finding the edges delineating the objects inside an image, and image decomposition closely related to image denoising, and attempting to partition an image into a smoother version of it named cartoon and its complementary oscillatory part called texture, with both local and nonlocal variational approaches. The first proposed model addresses the topology-preserving segmentation-guided registration problem in a variational framework. A second joint segmentation and registration model is introduced, theoretically and numerically studied, then tested on various numerical simulations. The last model presented in this work tries to answer a more specific need expressed by the CEREMA (Centre of analysis and expertise on risks, environment, mobility and planning), namely automatic crack recovery detection on bituminous surface images. Due to the image complexity, a joint fine structure decomposition and segmentation model is proposed to deal with this problem. It is then theoretically and numerically justified and validated on the provided images
Berard, Bergery Blandine. "Approximation du temps local et intégration par régularisation". Phd thesis, Université Henri Poincaré - Nancy I, 2007. http://tel.archives-ouvertes.fr/tel-00181777.
Testo completoPaditz, Ludwig. "Über die Annäherung der Verteilungsfunktionen von Summen unabhängiger Zufallsgrößen gegen unbegrenzt teilbare Verteilungsfunktionen unter besonderer Beachtung der Verteilungsfunktion der standardisierten Normalverteilung". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2013. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-114206.
Testo completoWith the presented work new contributions to basic research in the field of limit theorems of probability theory are given. Limit theorems for sums of independent random variables taking on the most diverse lines of research in probability theory an important place in modern times and are no longer only of theoretical interest. In the work results are presented to newer problems on the summation theory of independent random variables, at first time in the fifties and sixties of the 20th Century appeared in the literature and have been studied in the past few years with great interest. International two main directions have emerged in the theory of limit theorems: Firstly, the questions on the convergence speed of a cumulative distribution function converges to a predetermined limit distribution function, and on the other hand the questions on an error estimate for the limit distribution function at a finite summation process. First indefinite divisible limit distribution functions are considered, then the normal distribution is specifically discussed as a limit distribution. As characteristic parameters both moments or one-sided moments or pseudo-moments are used. The error estimates are stated both in uniform as well as non-uniform residual bounds including a description of the occurring absolute constants. Both the method of characteristic functions as well as direct methods (convolution method) can be further expanded as proof methods. Now for the error estimate, 1965 given by Bikelis, was the first time to estimate the appearing absolute constant C with C = 114.667 numerically. Furthermore, in the work of so-called limit theorems for moderate deviations are studied. Here also remainder estimates are derived for the first time. In recent years to the proof of limit theorems the chosen way of the convolution of distribution functions proved to be groundbreaking and determined the development of both the theory of limit theorems for moderate and large deviations as well as the investigation into the nonuniform estimates in the central limit theorem significantly. The convolution method is in the present thesis, the main instrument of proof. Thus, it was possible to obtain a series of results and obtain new numerical results in particular by means of electronic data processing
ALMEIDA, NETO Miguel Santana de. "Os padrões ecomorfológicos apresentados pelas espécies da ordem Characiformes (actinopterygii) são relacionadas com suas adaptações ecológicas?" Universidade Federal Rural de Pernambuco, 2012. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5441.
Testo completoMade available in DSpace on 2016-08-23T12:27:18Z (GMT). No. of bitstreams: 1 Miguel Santana de Almeida Neto.pdf: 1157651 bytes, checksum: 9441b1beb74a542d2c1f48a97e3fcee5 (MD5) Previous issue date: 2012-12-05
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The morphological patterns shown in the species result from the interactions between their phenotype, genotype, and environment through adaptive and evolutionary processes. Thus, this study aims to evaluate the role of phylogeny and feeding in the morphological patterns of the species of Characiformes order, testing the hypothesis that the environmental pressure interferes in the morphological patterns presented by species causing morphological divergence or convergence between them. The site selected for this research was the pond Curralinho, an marginal pond of the Rio São Francisco, located in the state of Pernambuco. In this work we used the twelve species of the Order Characiformes more abundant in the ecosystem evaluated, which were captured in the period from March/2007 to February/2008 Through morphological data and diet analysis, we found that segregation of Characiformes in morphologically distinct groups, reflecting dietary differences. Therefore, morphologically similar species tending to occupy the same trophic guild. The piscivorous Acestrorhynchus britskii, Acestrorhynchus lacustris, Hoplias malabaricus, Serrasalmus brandtii and Pygocentrus piraya showed morphological characteristics that allowed ingest relatively large prey. However, we observed differences in the efficacy of swimming performance of these piscivorous, indicating that the piscivorous that eat whole fish exhibit greater agility swimming performance in order to capture your evasive preys that presented adaptations to avoid and escape the predators. The species Roeboides xenodon and Leporinus reinhardti also preferably used fish in their diets, however, the morphology of these species did not show any adjustments found in majority of the piscivorous. The less swimming speed was evidentiated among the members of the guilds insectivorous and omnivorous, that using food items with lower mobility than fish, like insects, or immobile, such as vegetables. This lower efficiency in swimming performance does not seem to characterize a disadvantage for these species. These appear to preferentially occupy the margin of the water body, which offers greater resource availability for these fish. The relationship between morphology and trophic ecology was confirmed by the Mantel test. This test indicated that the ecological structure of the taxocenosis evaluated probably been shaped by evolutionary adaptations for use of a given resource. These adaptations may be evident when we observe the processes of adaptive convergence and divergence.
Os padrões morfológicos apresentados pelas espécies resultam da interação entre seu fenótipo, genótipo e ambiente, através de processos adaptativos e evolutivos. Dessa forma, este trabalho objetiva avaliar o papel da filogenia e do hábito alimentar nos padrões morfológicos das espécies da Ordem Characiformes, testando a hipótese de que a pressão ambiental interfere nos padrões morfológicos apresentados pelas espécies a ponto de causar divergência ou convergência morfológica entre elas. O local selecionado para esta pesquisa foi a lagoa Curralinho, uma lagoa marginal do Rio São Francisco, localizada no estado de Pernambuco. Neste trabalho foram utilizadas as doze espécies da Ordem Characiformes mais abundantes no ecossistema avaliado, sendo elas capturadas no período de março/2007 a fevereiro/2008. Através de dados morfológicos e análise da dieta, verifica-se que a segregação dos Characiformes em grupos morfologicamente distintos, refletiu de um modo geral, suas diferenças alimentares, com as espécies morfologicamente semelhantes propendendo a ocupar uma mesma categoria trófica. Os piscívoros Acestrorhynchus britskii, Acestrorhynchus lacustres, Hoplias malabaricus, Pygocentrus piraya e Serrasalmus brandtii apresentaram características morfológicas que os permitiram ingerir presas relativamente maiores. No entanto entre esses piscívoros observam-se diferenças na eficiência natatória, indicando que os piscívoros que ingerem peixes inteiros apresentam uma maior agilidade natatória para capturar suas presas evasivas, que se deslocam e apresentam adaptações para fugir de seus predadores. As espécies Roeboides xenodon e Leporinus reinhardti, também utilizaram preferencialmente peixes em suas dietas, no entanto, a morfologia dessas espécies não apresentou as adaptações encontradas na maioria dos piscívoros. A menor velocidade de natação foi evidenciada entre os integrantes das categorias insetívora e onívora, que utilizam itens alimentares com menor mobilidade que os peixes, como os insetos, ou imóveis, como os vegetais. Esta menor eficiência natatória não parece caracterizar uma desvantagem para essas espécies, visto que essas parecem ocupar preferencialmente as margens do corpo d’água, que oferece uma maior disponibilidade de recursos para estes peixes. A relação entre morfologia e ecologia trófica, confirmada pelo teste de Mantel, indica que provavelmente a estruturação ecológica da taxocenose avaliada vem sendo conformada por adaptações evolutivas para utilização de um determinado recurso. Essas adaptações podem ser evidenciadas, quando se observam os processos de convergência e divergência adaptativas.