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Tassignon, Hugo. "Solutions to non-stationary problems in wavelet space." Thesis, De Montfort University, 1997. http://hdl.handle.net/2086/13259.
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Johansson, Tomas. "Reconstruction of a stationary flow from boundary data." Licentiate thesis, Linköpings universitet, Kommunikations- och transportsystem, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-140141.
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We study a Cauchy problem arising in uid mechanics, involving the socalled stationary generalized Stokes system, where one should recover the ow from boundary measurements. The problem is ill-posed in the sense that the solution does not depend continuously on data. Two iterative procedures for solving this problem are proposed and investigated. These methods are regularizing and in each iteration one solves a series of well-posed problems obtained by changing the boundary conditions. The advantage with this approach, is that these methods place few restrictions on the domain and on the coe_cients of the problem. Also the structure of the equation is preserved. Well-posedness of the problems used in these procedures is demonstrated, i.e., that the problems have a unique solution that depends continuously on data. Since we have numerical applications in mind, we demonstrate well-posedness for the case when boundary data is square integrable. We give convergence proofs for both of these methods.
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Barr, Ronald I. "Planning and urban design strategies for addressing stationary noise related problems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/MQ63488.pdf.
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Le, Roux Christiaan. "Mixed variational problems associated with stationary viscous incompressible free boundary flows." Master's thesis, University of Cape Town, 1991. http://hdl.handle.net/11427/15965.
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Bibliography: pages 93-97.A strategy that is often used in the study of capillary free boundary (FB) problems for viscous incompressible flows is the following: (1) Ignore one of the boundary conditions at the FB and prove that for every chosen position of the FB the resultant problem, here called the auxiliary problem (AP), is well posed. (2) Establish regularity results for the solution of the AP. (3) Using (2) and the remaining boundary condition, determine the position of the FB. We study the existence and uniqueness of the weak solution(s) to the AP, i.e., step (1), under minimal regularity constraints on the data and domain. The analysis is carried out for stationary two-dimensional flows, governed by either the Stokes or Navier-Stokes equations, in the context of four standard examples. A Green's formula is derived which allows the AP to be formulated as a mixed variational problem in which the pressure and normal stress appear as Lagrange multipliers. Existence and uniqueness results are obtained by using the Ladyzhenskaya-Babuska-Brezzi theory for mixed problems. By analogy with step (3), the dependence of the normal stress on the position of the FB is investigated.
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Lin, Tianyu. "Some Stationary and Evolution Problems Governed by Various Notions of Monotone Operators." Master's thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/32783.
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The purpose of this work is to explore some notions of monotonicity for operators between Banach spaces and the applications to the study of boundary value problems (BVPs) and initial boundary value problems (IBVPs) for partial differential equations (PDEs), with the possibility in the end to examine new problems and provide some solutions. Variational approach will be used to reformulate these problems into stationary equations (in the case of BVPs) and evolution equations (in the case of IBVPs), where the underlined operators constructed as realizations of those problems in appropriate function spaces. This is known as weak formulation, which allows us to find weak solutions of the problems in a larger functions space rather than classical solutions that are sufficiently smooth. The theory of monotone and pseudomonotone operators will be applied to find existence theorems for stationary equations and evolution equations. In addition, the existence theorem for evolution equations with locally monotone operator will also be presented as a generalisation of the one with monotone operators. Another type of monotonicity so-called strict p-quasimonotonicity, which is defined in term of Young measures. This type of weaker, integrated version of monotonicity is directly applied in the study of elliptic and parabolic system of PDEs, the difficulty arises from dealing with this monotonicity is overcome by the theory of Young measures. The application of these monotonicity in the study of variational inequality will also be discussed. In particular, there is a new setting for strict p-quasimonotonicity in a particular type of elliptic variational inequalities, the proof of the new existence theorem will also be presented. Some open problems on the application of strict p-quasimonotonicity in the study of parabolic variational inequalities will also be discussed. Finally, we mention the theory of monotone and pseudomonotone operators in the study of second order evolution equations. A new setting of the local monotonicity in the second order evolution equations will be presented as well as the new existence theorem.
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Colville, Kevin. "An analysis of frictional effects in non-stationary contact problems for metal forming simulations." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33435.
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The finite element method (FEM) is widely used for the simulation of metal forming processes and has been successfully used in contact problems which arise in processes such as deep-drawing, punching, extrusion and rolling. All these processes involve friction between the contact surfaces: the sheet-metal workpiece and the toolpieces. The model of friction is thus an important part of any simulation of metal forming processes. Most FEM codes use a friction model that assumes that the contact surface is a plane. Attempts to address this problem have focused on the convective description of deformation, which has the advantage of being naturally extended to numerical methods like the FEM at the expense of additional computation and numerical complexity. The convective description is used in this work, which focuses on the numerical implementation of the objective measure. The effects of the rotation of the material contact point is taken into account by including objective time derivatives of the slipping (tangential) direction function. The objective rate of the direction function includes the surface spin induced by the rigid motion of a contact point sliding over the tool surface, and the material spin occurring during the elastic-plastic deformation of the blank. This is introduced by adapting the incremental relations of the friction slip. This thesis presents the results of numerical experiment to determine the influence that the rotation and convection of contact points has on the frictional stresses and slipping energy. Four different friction models are implemented within the finite element program ABAQUS and applied to simulations of standardmetal forming benchmark processes: the square-cup and s-rail deep drawing benchmarks of the Numisheet conferences, for which several experimental and numerical results are available to compare with the solution of a finite element simulation. The results for each metal-forming simulation are calculated for different friction models, and are compared and a choice made as to which is the “best” friction model for the process. Further, the reverse problem of determining the values of friction parameters by comparison of simulation and experimental results is performed for these benchmark problems. As there is yet no ideal friction model for all processes that are modelled, finding the most appropriate friction model by numerical means is proposed to improve the quality of a simulation.
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Fiscella, A. "VARIATIONAL PROBLEMS INVOLVING NON-LOCAL ELLIPTIC OPERATORS." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/245334.
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My thesis deals with nonlinear elliptic problems involving a non-local integrodifferential operator of fractional type. Our main results concern the existence of weak solutions for these problems and they are obtained using variational and topological methods.
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Klovienė, Neringa. "Non-stationary Poiseuille type solutions for the second grade fluid flow problem in cylindrical domains." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130124_081843-47698.
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In the dissertation one of the Rivlin-Erikson differential type fluids model – the second grade fluids flow problem is considered. The problem is studied in three different unbounded domains: • the two-dimensional channel, • the three-dimensional axially symmetric pipe, • the three-dimensional pipe with an arbitrary cross section. For the two-dimensional channel and the three-dimensional axially symmetric pipe we assume that the initial data and the external force have only the last component and are independent of the coordinate x_n: u_0(x,t)=(0, …, u_{n0}(x’,t)), f(x,t)=(0, …, f_n(x’,t)). We look for an unidirectional (having just the last component) solution u(x,t) =(0, …, u_n(x’,t)), which satisfies the flux condition. Such solution we call Poiseuille type solution. In the first two cases the existence of a unique unidirectional Poiseuille type solution is proved and the relation between the flux of the velocity field and the pressure drop (the gradient of the pressure) is found. The analogous results were obtained for the time periodic problem in the two-dimensional channel. It is shown that in the three-dimensional pipe with an arbitrary cross section the unidirectional solution does not exists even if data are unidirectional. However, for sufficiently small data in this case exists a unique solution having all three components u(x’,t)=( u_1, u_2, u_3). To analyze the problem we use Galerkin method with the special bases.Disertacijoje nagrinėjamas vienas iš Rivlin-Eriksono diferencialinio tipo skysčių matematinių modelių – antrojo laipsnio skysčių tekėjimo uždavinys. Problema analizuojama su papildomai užduota srauto sąlyga trijose skirtingose srityse: • begalinėje juostoje, • begaliniame sukimosi cilindre, • begaliniame vamzdyje su bet kokiu skerspjūviu. Tariama, kad pradinio greičio ir išorės jėgų vektoriai nepriklauso nuo paskutinės koordinatės ir yra išreikšti pavidalu u_0(x,t)=(0, …, u_{n0}(x’,t)), f(x,t)=(0, …, f_n(x’,t)). Ieškoma antrojo laipsnio skysčių tekėjimo uždavinio Puazeilio tipo u(x,t) =(0, …, u_n(x’,t)) sprendinio. Begalinėje dvimatėje juostoje ir begaliniame trimačiame sukimosi cilindre įrodytas kryptinio Puazeilio tipo sprendinio egzistavimas ir rastas sąryšis tarp srauto ir slėgio gradiento. Analogiški rezultatai gauti pradiniam ir kraštiniam antrojo laipsnio skysčių tekėjimo uždaviniui periodinėje pagal laiką begalinėje dvimatėje juostoje. Darbe parodyta, kad begaliniame trimačiame vamzdyje, su bet kokiu skerspjūviu, kryptinis (priklausantis tik nuo paskutinės komponentės) Puazeilio tipo sprendinys neegzistuoja net jei pradiniai duomenys yra kryptiniai. Nagrinėjamas bendresnis atvejis, kai Puazeilio tipo sprendinys priklauso nuo visų trijų komponenčių u(x’,t)=( u_1, u_2, u_3). Disertacijoje įrodyta, kad esant mažiems pradiniams duomenims egzistuoja vienintelis uždavinio sprendinys. Sprendžiant buvo naudojamas Galiorkino aproksimacijų metodas ir specialios bazės.
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Gillard, Frédéric. "Conception et réalisation d’un micro-spectromètre dans l’infrarouge." Thesis, Paris 11, 2012. http://www.theses.fr/2012PA112043/document.
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Pour répondre au besoin de miniaturisation des spectromètres de terrain travaillant dans l’infrarouge, l’ONERA a développé un nouveau concept baptisé MICROSPOC. Ce dispositif est un détecteur infrarouge auquel a été intégré un interféromètre à deux ondes, constituant un spectromètre statique par transformée de Fourier. Ce plan focal infrarouge modifié, qui fusionne la fonction interférométrique et la fonction de détection, associé à une optique de tête simplifiée, permet d’envisager la réalisation d’instruments très compacts. L’objectif de cette thèse est de concevoir un spectromètre infrarouge miniature basé sur le dispositif MICROSPOC. Dans un premier temps, un travail théorique a été mené, dans l’objectif de dimensionner un système optique très compact. Notre choix s’étant orienté vers un système optique de collection (le détecteur voit une source étendue à distance finie), l’étude de l’acceptance angulaire de MICROSPOC dans ces conditions d’éclairement est indispensable afin de prévoir le contraste et la forme des franges d’interférence. Les résultats montreront la grande acceptance angulaire de MICROSPOC.Dans un second temps, un démonstrateur basé sur un composant MICROSPOC et sur le système optique simplifié a été réalisé. Ce démonstrateur a été caractérisé en laboratoire puis utilisé sur le terrain lors d’une campagne de mesures. Ces différentes exploitations ont montré la robustesse de l’instrument malgré l’obtention d’interférogrammes présentant divers défauts.Dans un troisième temps, une chaîne de traitement a été développée afin d’estimer un spectre à partir d’un interférogramme obtenu à l’aide du démonstrateur. Du fait des caractéristiques intrinsèques de MICROSPOC, la transformée de Fourier n’est pas la meilleure solution pour estimer un spectre. Nous l’avons montré en nous intéressant aux effets des disparités de longueur d’onde de coupure du détecteur sur l’estimation d’un spectre. Nous nous sommes alors tournés vers une approche consistant à utiliser la caractérisation spectrale de l’instrument pour inverser la mesure. Cette approche donne des résultats satisfaisants.Enfin, le but principal de cette thèse a été élargi par la conception et la réalisation de différents démonstrateurs combinant une fonction d’imagerie à une fonction de spectrométrie. Les premières pistes pour la conception d’un spectromètre qui tient dans la main ont été donnéesIn order to satisfy the need for handheld infrared spectrometers, the ONERA developed a new concept called MICROSPOC. This device is an infrared focal plane array with a built-in two-wave wedge-like interferometer and forms a static Fourier-transform spectrometer. This modified focal plane array, which merges the detection function and the interferometric function, in association with a simplified optical system, allows to consider the realisation of a much compact instrument. The goal of this thesis is to design and to realize a miniaturized infrared spectrometer based on the MICROSPOC concept.Firstly, a theoritical work has been led in order to design a compact optical system. Since we have chosen a collection optical system (the focal plane array sees an extended source placed at a finite distance), the study of MICROSPOC angular acceptance in these lightening conditions is needed in order to predict the contrast and the shape of interference fringes. The huge angular acceptance of MICROSPOC will be established with the results of this study.Secondly, a demonstrator based on MICROSPOC device and on the simplified optical system has been realized. This demonstrator has been caracterized in the laboratory and used in real conditions of a measurement campaign. These different exploitations have shown the robustness of the instrument despite some defaults on acquired interferograms.Then, a processing chain has been developed in order to estimate a spectrum from an interferogram acquired with our demonstrator. Considering the MICROSPOC’s own characteristics, the Fourier-transform is not the best way to estimate a spectrum. We have come to this conclusion by studying the effects of cut-off wavelenghts disparities of the detector on the spectrum estimation. At this point we have considered an approach that consists of using the spectral characterization of the instrument in order to inverse the measure. This approach gives satisfying results.Finaly, the main goal has been widened with the design and the realisation of other instruments that combine a spectrometric function and a imaging function. The first elements for the design of a handheld spectrometer have been given
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Menoni, Jose Antonio. "Formulação e implementação da versão direta do metodo dos elementos de contorno para tratamento de problemas acusticos estacionarios bidimensionais diretos e inversos." [s.n.], 2004. http://repositorio.unicamp.br/jspui/handle/REPOSIP/263958.
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Orientador: Euclides de Mesquita NetoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica
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Resumo: Este trabalho trata da formulação e da implementação da versão direta do Método dos Elementos de Contorno (MEC) para tratamento de problemas acústicos bidimensionais estacionários regidos pelo operador diferencial de Helrnholtz. São abordados tanto problemas internos, associados a domínios limitados, quanto problemas externos, associados a domínios ilimitados. A tese ainda aborda a solução de problemas diretos e inversos. A transformação da equação de Helrnholtz em Equação Integral de Contorno, bem como a síntese de sua Solução Fundamental é recuperada de forma detalhada no texto. Para o caso de problemas internos duas técnicas são estudadas para recuperação de grandezas modais de cavidades acústicas. A primeira é baseada na pesquisa direta das raÍzes do polinômio característico e a segunda é baseada na informação obtida a partir de Funções de Resposta em Freqüência sintetizadas pelo MEC. Os problemas da radiação e espalhamento acústico são formulados, implementados e validados. O trabalho apresenta ainda a solução de problemas inversos, no qual as variáveis acústicas em um contorno geométrico conhecido são determinadas a partir de medições em uma superficie fechada e que envolve o corpo radiante. Duas técnicas são utilizadas no processo inverso, a Decomposição em Valores Singulares e a técnica de regularização de Tikhonov. Discute-se a precisão e eficiência destas técnicas em função dos parâmetros que são variáveis presentes nestas técnicas
Abstract: The present Thesis reports a formulation and an implementation of the direct version of the Boundary Element Method (BEM) to model direct and indirect bidimensional stationary acoustic problems governed by the Helrnholz differential operator. Both internal and external problems, associated, respectively to bounded and unbounded domains, are treated in the analysis. The transformation of the Helmholtz differential equation into an equivalent Boundary Integral Equation (BIE) and the synthesis of its Fundamental Solution is recovered in detail. For internal problem two techniques are employed to obtain modal quantities of acoustic cavities. The fIrs is the direct search method of the characteristic polynomial roots. The second strategy is based on numerical Frequency Response Functions, synthesized by the BEM. Radiation and scatter problems are formulated, implemented and validated within the realm of the Boundary Element Method. The present work still addresses the solution of an inverse problem. The inverse problem consists of determining the acoustic variables on the boundary of a radiating or scattering body of known geometry, based on the acoustic fIelds measured over a c10sed surface which embodies the analized body. Two technique to solve the inversion problem are discussed. The fIrst is the Single Value Decomposition strategy and the other is the Tikhonov regularization strategy. The accuracy of this techniques are discussed as functions of the internal parameters which are intrinsic to those strategies
Doutorado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Kuhl, Christian [Verfasser]. "Stationäre Lösungen des N-Wirbel-Problems der Fluiddynamik / Christian Kuhl." Gießen : Universitätsbibliothek, 2014. http://d-nb.info/1068541024/34.
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Kawagoe, Daisuke. "Regularity of solutions to the stationary transport equation with the incoming boundary data." Kyoto University, 2018. http://hdl.handle.net/2433/232413.
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Surowiec, Thomas Michael. "Explicit stationarity conditions and solution characterization for equilibrium problems with equilibrium constraints." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2010. http://dx.doi.org/10.18452/16087.
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Die vorliegende Arbeit beschaeftigt sich mit Gleichgewichtsproblemen unter Gleichgewichtsrestriktionen, sogenannten EPECs (Englisch: Equilibrium Problems with Equilibrium Constraints). Konkret handelt es sich um gekoppelte Zwei-Ebenen-Optimierungsprobleme, bei denen Nash- Gleichgewichte fuer die Entscheidungen der oberen Ebene gesucht sind. Ein Ziel der Arbeit besteht in der Formulierung dualer Stationaritaetsbedingungen zu solchen Problemen. Als Anwendung wird ein oligopolistisches Wettbewerbsmodell fuer Strommaerkte betrachtet. Zur Gewinnung qualitativer Hypothesen ueber die Struktur der betrachteten Modelle (z.B. Inaktivitaet bestimmter Marktteilnehmer) aber auch fuer moegliche numerische Zugaenge ist es wesentlich, EPEC-Loesungen explizit bezueglich der Eingangsdaten des Problems zu formulieren. Der Weg dorthin erfordert eine Strukturanalyse der involvierten Optimierungsprobleme (constraint qualifications, Regularitaet), die Herleitung von Stabilitaetsresultaten bestimmter mengenwertiger Abbildungen und die Nutzung von Transformationsformeln fuer die sogenannte Ko-Ableitung. Weitere Schwerpunkte befassen sich mit der Beziehung zwischen verschiedenen dualen Stationaritaetstypen (S- und M-Stationaritaet) sowie mit stochastischen Erweiterungen der betrachteten Problemklasse, sogenannten SEPECs.This thesis is concerned with equilibrium problems with equilibrium constraints or EPECs. Concretely, we consider models composed by coupling together two-level optimization problems, the upper-level solutions to which are non-cooperative (Nash-Cournot) equilibria. One of the main goals of the thesis involves the formulation of dual stationarity conditions to EPECs. A model of oligopolistic competition for electricity markets is considered as an application. In order to profit from qualitative hypotheses concerning the structure of the considered models, e.g., inactivity of certain market participants at equilibrium, as well as to provide conditions useful for numerical procedures, the ablilty to formulate EPEC solutions in relation to the input data of the problem is of considerable importance. The way to do this requires a structural analysis of the involved optimization problems, e.g., constraints qualifications, regularity; the derivation of stability results for certain multivalued mappings, and the usage of transformation formulae for so-called coderivatives. Further important topics address the relationship between various dual stationarity types, e.g., S- and M-stationarity, as well as the extension of the considered problem classes to a stochastic setting, i.e., stochastic EPECs or SEPECs.
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Princ, Vojtěch. "Management parkování." Master's thesis, Vysoká škola ekonomická v Praze, 2008. http://www.nusl.cz/ntk/nusl-76939.
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The objective of this thesis is to design the appropriate parking management for downtown of Jindrichuv Hradec. The theoretical part is focused on the traffic problem and its negative effects on environment of cities in relation to increase in private car transport in recent years. In the next chapter, parking management and its specific strategies are described as instruments solving problems with urban transport including its static and dynamic part. Practical part includes description of current traffic conditions and accessibility of the town centre of Jindrichuv Hradec. The description results from information obtained by personal mapping of location and measuring of parking occupancy. The proposed solution of certain parking policies that result in more efficient use of parking resources with minimized traffic impacts on historical centre of town follows.
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Kaulakytė, Kristina. "Nonhomogeneous boundary value problem for the stationary Navier-Stokes system in domains with noncompact boundaries." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2013~D_20130124_081640-17274.
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In the thesis there is studied nonhomogenous boundary value problem for the stationary Navier-Stokes system in domains which may have two types of outlets to infinity: paraboloidal and layer type. The boundary is multiply connected. It consists of connected noncompact components, forming the outer boundary, and connected compact components, forming the inner boundary. We suppose that the fluxes over the components of the inner boundary are sufficiently small, while we do not impose any restrictions on fluxes over the infinite components of the outer boundary. We prove that the formulated problem admits at least one weak solution which, depending on the geometry of the domain, may have either finite or infinite Dirichlet integral.Disertacijoje nagrinėjama stacionari Navjė-Stokso sistema su nehomogenine kraštine sąlyga srityse su išėjimais į begalybę. Bendru atveju išėjimai į begalybę gali būti tiek paraboloidiniai, tiek sluoksnio tipo. Srities kraštą sudaro baigtinis skaičius nekompaktiškų jungių komponenčių, kurios suformuoja išorininį kraštą, ir baigtinis skaičius kompaktiškų jungių komponenčių, kurios suformuoja vidinį srities kraštą. Darydami prielaidą, kad srautai per vidinio krašto komponentes yra pakankamai maži, o srautų dydžiui per išorinio krašto komponentes nedarant jokių apribojimų, įrodome suformuluoto uždavinio bent vieno sprendinio egzistavimą. Priklausomai nuo srities geometrijos, uždavinio sprendinys gali turėti tiek baigtinį, tiek begalinį Dirichlė integralą.
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May, Ute [Verfasser]. "Asymptotic estimates to a free boundary problem for the stationary Navier-Stokes equations / Ute May." Aachen : Hochschulbibliothek der Rheinisch-Westfälischen Technischen Hochschule Aachen, 2014. http://d-nb.info/1049821572/34.
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Steneberg, Steffen C. [Verfasser]. "Lineare Modelle für stationäre und transiente Cycle-Shop Scheduling-Probleme / Steffen C. Steneberg." München : Verlag Dr. Hut, 2013. http://d-nb.info/1042878501/34.
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Clausen, Hartmut [Verfasser], and Lothar [Akademischer Betreuer] Streitferdt. "Ambulant oder stationär - die ökonomische Vorteilhaftigkeit der Angebotsformen in der Pflege / Hartmut Clausen. Betreuer: Lothar Streitferdt." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2013. http://d-nb.info/1031756655/34.
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Copros, Guillaume. "Stationnarité forte sur des graphes discrets ou quantiques." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30088/document.
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Dans cette thèse, on s'intéresse à la notion de temps fort de stationnarité et à celle, étroitement liée, de dual de stationnarité forte. Ces outils permettent d'étu- dier la convergence de processus ergodiques, en déterminant un instant aléatoire où l'équilibre est atteint. Les espaces d'état des processus considérés ici sont des graphes continus ou discrets. Dans la première partie, on considère le cas discret, et on dégage une condition nécessaire et suffisante à l'existence, pour n'importe quelle loi initiale, d'un temps fort de stationnarité fini. Pour cela, on construit explicitement un dual de station- narité forte, à valeurs dans l'ensemble des parties connexes du graphe, qui évolue à chaque étape en ajoutant ou en enlevant des points de sa frontière. Lorsque cette opération sépare l'ensemble dual en plusieurs parties, afin de ne pas le déconnecter, une de ces parties est choisie au hasard, avec une probabilité proportionnelle à son poids par la mesure invariante. On s'intéresse également au comportement général d'un processus dual, et on donne quelques exemples différents de celui construit précédemment. Dans la deuxième partie, on traite le cas continu, et le processus étudié est alors une diffusion. On caractérise notamment sa mesure invariante, et on explicite un générateur infinitésimal qui devrait être celui d'un processus dual. Néanmoins, ce cas s'avère plus compliqué que le cas discret. Le processus dual n'est donc construit que pour un mouvement brownien sur un graphe particulier, comme l'unique so- lution d'un problème de martingale. Des pistes sont présentées pour traiter des diffusions sur des graphes plus généraux, notamment en utilisant la convergence d'une suite de processus de saut tels que ceux présentés dans la première partieIn this thesis, we are interested in the notion of strong stationary time, and in that, strongly connected, of strong stationary dual. These tools allow to study the convergence of ergodic processes, by determining a random time when the equilibrium is reached. The state space of the considered processes are discrete or continuous graphs. In the first part, we consider the discrete case, and we explicit a necessary and sufficient condition to the existence, for any initial distribution, of a finite strong stationary time. To do so, we construct explicitly a strong stationary dual, with values in the set of connected subsets of the graph, which evolves at each step by adding or removing some points at its border. Whenever this operation separates the dual set in several parts, in order not to disconnect it, one of these parts is chosen randomly, with a probability proportionnal to its weight relative to the invariant distribution. We also study the general behaviour of any dual process,2 and we give some other examples. In the second part, we deal with the continuous case, and the studied process is then a diffuion. We caracterize its invariant distribution, and we explicit an infinitesimal generator, which is expected to be that of a dual process. Nevertheless, this case turns out to be a little more involved that the discrete one. The dual process is thus constructed only for a brownian motion on a particular graph, as the unique solution of a martingale problem. Some leads are given to solve the case of diffusions on more general graphs, especially by using the convergence of a sequence of jump processes such as those presented in the first part
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Brachna, Róbert. "Stanovení anizotropie tepelné vodivosti polymerních chladičů pro chlazení elektroniky." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2021. http://www.nusl.cz/ntk/nusl-445460.
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The master's thesis focuses on creating a numerical model of a polymeric heat sink with emphasis on its significant thermal conductivity anisotropy. This anisotropy is caused by highly thermally conductive graphite filler. Its final orientation is given by the melt flow inside the mould cavity during injection molding. The numerical model is created on the basis of a heat sink prototype subjected to experimental measurements, whose physical conditions are reliably replicated by the model. The determination of anisotropy is divided into two parts. The qualitative part is based on the fracture analysis of the heat sink prototype and determines the principal directions of the conductivity tensor in individual sections of the geometry. The computation of principal conductivities falls into the quantitative part, in which this task is formulated as an inverse heat conduction problem. The input data for the proposed task are experimentally obtained temperatures at different places of the geometry. The values of principal conductivities are optimized to minimize the difference between the measured and simulated temperatures.
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Nordmann, Erik Michael [Verfasser]. "Psychiatrische Familienpflege und stationäre Heimunterbringung für Jugendliche im Vergleich : eine Studie zu differentieller Indikationsstellung und Outcome von Jugendhilfemaßnahmen für psychisch auffällige Jugendliche / Erik Nordmann." Ulm : Universität Ulm. Medizinische Fakultät, 2011. http://d-nb.info/1018707107/34.
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Cálipo, Leonardo Gurgel. "Análise do problema de controle de estoques dinâmico para demanda não estacionária e lead-time positivo." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/3/3136/tde-22052015-155307/.
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O problema de controle de estoques com demanda não estacionária e lead-time positivo tem se tornado cada vez mais relevante em virtude da crescente tendência de redução do ciclo de vida dos produtos e internacionalização das cadeias de suprimentos. Embora haja uma solução exata para a minimização do custo esperado da política de estoques para este cenário, baseado no método de programação dinâmica, o custo computacional deste método ainda é considerado elevado. Este trabalho detalha e avalia através de simulação o método exato e duas aproximações para a minimização do custo esperado da política de estoques, em termos do desempenho em custo e eficiência computacional. Os resultados experimentais permitem a análise dos métodos disponíveis. Enquanto a abordagem heurística de Bollapragada e Morton, que utiliza o nivelamento da demanda não estacionária, perde desempenho de custo com o aumento do lead-time, a nova heurística proposta, que aproxima os parâmetros da política ótima por valores limitantes, produz resultados sucessivamente melhores com o aumento do lead-time.The inventory control problem with nonstationary demand and positive lead-time has become increasingly important due to the growing trend of reduction in product life cycle and internationalization of the supply chain. Although there is an exact solution to the minimization of the expected cost of inventory policy on this environment, through the method of dynamic programming, the computational cost of this method is still considered high. This work details and evaluates through simulation the exact method and two heuristic solutions for the minimization of expected cost of inventory policy, in terms of cost performance and computational efficiency. The experimental results allow the analysis of the available methods. While the Bollapragada and Morton heuristic approach, which levels the non-stationary demand, decreases the cost performance when lead-time is increased, the new heuristic proposed, that approximates the optimal policy parameters by limiting values, successively produces better results with increasing lead-times.
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Fleischmann, Carolin [Verfasser], Oorschot Birgitt [Gutachter] van, Peter [Gutachter] Kranke, and Carmen [Gutachter] Roch. "Eine Analyse der Verlegungen von der Palliativstation in die stationäre Hospizversorgung: Ist der Einsatz von Prognosescores hilfreich? / Carolin Fleischmann ; Gutachter: Birgitt van Oorschot, Peter Kranke, Carmen Roch." Würzburg : Universität Würzburg, 2021. http://d-nb.info/1225296005/34.
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Higaki, Mitsuo. "Analysis of the planar exterior Navier-Stokes problem with effects related to rotation of the obstacle." Kyoto University, 2019. http://hdl.handle.net/2433/236605.
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Latocha, Vladimir. "Deux problemes en transport des particules chargees intervenant dans la modelisation d'un propulseur ionique." Phd thesis, INSA de Toulouse, 2001. http://tel.archives-ouvertes.fr/tel-00002194.
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La modélisation des propulseurs ioniques de type SPT pose de nombreux problèmes dans le domaine du transport des particules chargées. Nous nous
intéressons à deux de ces problèmes, à savoir le transport des électrons et
le calcul du potentiel électrique.
Le transport des électrons résulte de l'influence conjuguée des champs
(électrique et magnétique) établis dans la cavité du propulseur et des
collisions des électrons (dans la cavité et avec la paroi limitant celle-ci).
Nous avons participé au développement d'un modèle SHE (Spherical Harmonics
Expansion) qui résulte d'une analyse asymptotique de l'équation de Boltzmann
munie de conditions de réflexion aux bords. Ce modèle permet d'approcher la
fonction de distribution en énergie des électrons en résolvant une
équation de diffusion dans un espace \{position, énergie\}. Plus précisément,
nous avons étendu une démarche existante au cas où les collisions en volume
(excitation, ionisation) et les collisions inélastiques à la paroi
(attachement et émission secondaire) sont prises en compte. Enfin, nous
avons écrit un code de résolution du modèle SHE, dont les résultats ont
été comparés avec ceux d'une méthode de Monte Carlo.
\vspace*{1mm}
Dans un deuxième temps, nous avons étudié le calcul du potentiel électrique.
La présence du champ magnétique impose d'écrire le courant d'électrons sous
la forme ${\cal J}=\sigma \nabla W$
où W est le potentiel électrique et le tenseur de conductivité $\sigma$
est fortement anisotrope compte tenu des grandeurs physiques en jeu dans
le SPT. Pour résoudre $\mbox{div }{\cal J}(x,y)=S(x,y)$,
nous avons implémenté une méthode de volumes finis
sur maillage cartésien permettant de résoudre ce problème elliptique
anisotrope, et nous avons vérifié qu'elle échouait lorsque le rapport
d'anisotropie devenait grand. Aussi nous avons développé une méthode de
paramétrisation, qui consiste à extrapoler la solution d'un problème
anisotrope à l'aide d'une suite de problèmes isotropes. Cette méthode a
donné des résultats encourageants pour de forts rapports d'anisotropie,
et devrait nous permettre d'atteindre des cas réels.
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Bösel, Maren [Verfasser], and Henning [Akademischer Betreuer] Schauenburg. "Integration von sozialarbeiterischen Interventionen in die stationäre psychosomatisch-psychotherapeutische Krankenhausbehandlung. Eine Erhebung sozialer Probleme und sozialtherapeutischer Beratungsfoki von Patienten in konfliktorientierten und strukturbezogenen Behandlungssettings / Maren Bösel ; Betreuer: Henning Schauenburg." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1211820718/34.
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Mourya, Rahul Kumar. "Contributions to image restoration : from numerical optimization strategies to blind deconvolution and shift-variant deblurring." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSES005/document.
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L’introduction de dégradations lors du processus de formation d’images est un phénomène inévitable: les images souffrent de flou et de la présence de bruit. Avec les progrès technologiques et les outils numériques, ces dégradations peuvent être compensées jusqu’à un certain point. Cependant, la qualité des images acquises est insuffisante pour de nombreuses applications. Cette thèse contribue au domaine de la restauration d’images. La thèse est divisée en cinq chapitres, chacun incluant une discussion détaillée sur différents aspects de la restauration d’images. La thèse commence par une présentation générale des systèmes d’imagerie et pointe les dégradations qui peuvent survenir ainsi que leurs origines. Dans certains cas, le flou peut être considéré stationnaire dans tout le champ de vue et est alors simplement modélisé par un produit de convolution. Néanmoins, dans de nombreux cas de figure, le flou est spatialement variable et sa modélisation est plus difficile, un compromis devant être réalisé entre la précision de modélisation et la complexité calculatoire. La première partie de la thèse présente une discussion détaillée sur la modélisation des flous spatialement variables et différentes approximations efficaces permettant de les simuler. Elle décrit ensuite un modèle de formation de l’image générique. Puis, la thèse montre que la restauration d’images peut s’interpréter comme un problème d’inférence bayésienne et ainsi être reformulé en un problème d’optimisation en grande dimension. La deuxième partie de la thèse considère alors la résolution de problèmes d’optimisation génériques, en grande dimension, tels que rencontrés dans de nombreux domaines applicatifs. Une nouvelle classe de méthodes d’optimisation est proposée pour la résolution des problèmes inverses en imagerie. Les algorithmes proposés sont aussi rapides que l’état de l’art (d’après plusieurs comparaisons expérimentales) tout en supprimant la difficulté du réglage de paramètres propres à l’algorithme d’optimisation, ce qui est particulièrement utile pour les utilisateurs. La troisième partie de la thèse traite du problème de la déconvolution aveugle (estimation conjointe d’un flou invariant et d’une image plus nette) et suggère différentes façons de contraindre ce problème d’estimation. Une méthode de déconvolution aveugle adaptée à la restauration d’images astronomiques est développée. Elle se base sur une décomposition de l’image en sources ponctuelles et sources étendues et alterne des étapes de restauration de l’image et d’estimation du flou. Les résultats obtenus en simulation suggèrent que la méthode peut être un bon point de départ pour le développement de traitements dédiés à l’astronomie. La dernière partie de la thèse étend les modèles de flous spatialement variables pour leur mise en oeuvre pratique. Une méthode d’estimation du flou est proposée dans une étape d’étalonnage. Elle est appliquée à un système expérimental, démontrant qu’il est possible d’imposer des contraintes de régularité et d’invariance lors de l’estimation du flou. L’inversion du flou estimé permet ensuite d’améliorer significativement la qualité des images. Les deux étapes d’estimation du flou et de restauration forment les deux briques indispensables pour mettre en oeuvre, à l’avenir, une méthode de restauration aveugle (c’est à dire, sans étalonnage préalable). La thèse se termine par une conclusion ouvrant des perspectives qui pourront être abordées lors de travaux futursDegradations of images during the acquisition process is inevitable; images suffer from blur and noise. With advances in technologies and computational tools, the degradations in the images can be avoided or corrected up to a significant level, however, the quality of acquired images is still not adequate for many applications. This calls for the development of more sophisticated digital image restoration tools. This thesis is a contribution to image restoration. The thesis is divided into five chapters, each including a detailed discussion on different aspects of image restoration. It starts with a generic overview of imaging systems, and points out the possible degradations occurring in images with their fundamental causes. In some cases the blur can be considered stationary throughout the field-of-view, and then it can be simply modeled as convolution. However, in many practical cases, the blur varies throughout the field-of-view, and thus modeling the blur is not simple considering the accuracy and the computational effort. The first part of this thesis presents a detailed discussion on modeling of shift-variant blur and its fast approximations, and then it describes a generic image formation model. Subsequently, the thesis shows how an image restoration problem, can be seen as a Bayesian inference problem, and then how it turns into a large-scale numerical optimization problem. Thus, the second part of the thesis considers a generic optimization problem that is applicable to many domains, and then proposes a class of new optimization algorithms for solving inverse problems in imaging. The proposed algorithms are as fast as the state-of-the-art algorithms (verified by several numerical experiments), but without any hassle of parameter tuning, which is a great relief for users. The third part of the thesis presents an in depth discussion on the shift-invariant blind image deblurring problem suggesting different ways to reduce the ill-posedness of the problem, and then proposes a blind image deblurring method using an image decomposition for restoration of astronomical images. The proposed method is based on an alternating estimation approach. The restoration results on synthetic astronomical scenes are promising, suggesting that the proposed method is a good candidate for astronomical applications after certain modifications and improvements. The last part of the thesis extends the ideas of the shift-variant blur model presented in the first part. This part gives a detailed description of a flexible approximation of shift-variant blur with its implementational aspects and computational cost. This part presents a shift-variant image deblurring method with some illustrations on synthetically blurred images, and then it shows how the characteristics of shift-variant blur due to optical aberrations can be exploited for PSF estimation methods. This part describes a PSF calibration method for a simple experimental camera suffering from optical aberration, and then shows results on shift-variant image deblurring of the images captured by the same experimental camera. The results are promising, and suggest that the two steps can be used to achieve shift-variant blind image deblurring, the long-term goal of this thesis. The thesis ends with the conclusions and suggestions for future works in continuation of the current work
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Abramowicz, Konrad. "Numerical analysis for random processes and fields and related design problems." Doctoral thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-46156.
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In this thesis, we study numerical analysis for random processes and fields. We investigate the behavior of the approximation accuracy for specific linear methods based on a finite number of observations. Furthermore, we propose techniques for optimizing performance of the methods for particular classes of random functions. The thesis consists of an introductory survey of the subject and related theory and four papers (A-D). In paper A, we study a Hermite spline approximation of quadratic mean continuous and differentiable random processes with an isolated point singularity. We consider a piecewise polynomial approximation combining two different Hermite interpolation splines for the interval adjacent to the singularity point and for the remaining part. For locally stationary random processes, sequences of sampling designs eliminating asymptotically the effect of the singularity are constructed. In Paper B, we focus on approximation of quadratic mean continuous real-valued random fields by a multivariate piecewise linear interpolator based on a finite number of observations placed on a hyperrectangular grid. We extend the concept of local stationarity to random fields and for the fields from this class, we provide an exact asymptotics for the approximation accuracy. Some asymptotic optimization results are also provided. In Paper C, we investigate numerical approximation of integrals (quadrature) of random functions over the unit hypercube. We study the asymptotics of a stratified Monte Carlo quadrature based on a finite number of randomly chosen observations in strata generated by a hyperrectangular grid. For the locally stationary random fields (introduced in Paper B), we derive exact asymptotic results together with some optimization methods. Moreover, for a certain class of random functions with an isolated singularity, we construct a sequence of designs eliminating the effect of the singularity. In Paper D, we consider a Monte Carlo pricing method for arithmetic Asian options. An estimator is constructed using a piecewise constant approximation of an underlying asset price process. For a wide class of Lévy market models, we provide upper bounds for the discretization error and the variance of the estimator. We construct an algorithm for accurate simulations with controlled discretization and Monte Carlo errors, andobtain the estimates of the option price with a predetermined accuracy at a given confidence level. Additionally, for the Black-Scholes model, we optimize the performance of the estimator by using a suitable variance reduction technique.
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Yeung, Deryck. "Maximally smooth transition: the Gluskabi raccordation." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42756.
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The objective of this dissertation is to provide a framework for constructing a transitional behavior, connecting any two trajectories from a set with a particular characteristic, in such a way that the transition is as inconspicuous as possible. By this we mean that the connection is such that the characteristic behavior persists during the transition. These special classes include stationary solutions, limit cycles etc. We call this framework the Gluskabi raccordation. This problem is motivated from physical applications where it is often desired to steer a system from one stationary solution or periodic orbit to another in a ̒smooth̕ way. Examples include motion control in robotics, chemical process control and quasi-stationary processes in thermodynamics, etc. Before discussing the Gluskabi raccordations of periodic behaviors, we first study several periodic phenomena. Specifically, we study the self- propulsion of a number of legless, toy creatures based on differential friction under periodic excitations. This friction model is based on viscous friction which is predominant in a wet environment. We investigate the effects of periodic and optimal periodic control on locomotion. Subsequently, we consider a control problem of a stochastic system, under the basic constraint that the feedback control signal and the observations from the system cannot use the communication channel simultaneously. Hence, two modes of operation result: an observation mode and a control mode. We seek an optimal periodic regime in a statistical steady state by switching between the observation and the control mode. For this, the duty cycle and the optimal gains for the controller and observer in either mode are determined.
We then investigate the simplest special case of the Gluskabi raccordation, namely the quasi-stationary optimal control problem. This forces us to revisit the classical terminal controller. We analyze the performance index as the control horizon increases to infinity. This problem gives a good example where the limiting operation and integration do not commute. Such a misinterpretation can lead to an apparent paradox. We use symmetrical components (the parity operator) to shed light on the correct solution.
The main part of thesis is the Gluskabi raccordation problem. We first use several simple examples to introduce the general framework. We then consider the signal Gluskabi raccordation or the Gluskabi raccordation without a dynamical system. Specifically, we present the quasi-periodic raccordation where we seek the maximally ̒smooth̕ transitions between two periodic signals. We provide two methods, the direct and indirect method, to construct these transitions. Detailed algorithms for generating the raccordations based on the direct method are also provided. Next, we extend the signal Gluskabi raccordation to the dynamic case by considering the dynamical system as a hard constraint. The behavioral modeling of dynamical system pioneered by Willems provides the right language for this generalization. All algorithms of the signal Gluskabi raccordation are extended accordingly to produce these ̒smooth̕ transition behaviors.
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Vasseur, Baptiste. "Étude de problèmes différentiels elliptiques et paraboliques sur un graphe." Thesis, Littoral, 2014. http://www.theses.fr/2014DUNK0400/document.
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Après une présentation des notations usuelles de la théorie des graphes, on étudie l'ensemble des fonctions harmoniques sur les graphes, c'est à dire des fonctions dont le laplacien est nul. Ces fonctions forment un espace vectoriel et sur un graphe uniformément localement fini, on montre que cet espace vectoriel est soit de dimension un, soit de dimension infinie. Lorsque le graphe comporte une infinité de cycles, ce résultat tombe en défaut et on exhibe des exemples qui montrent qu'il existe un graphe sur lequel les harmoniques forment un espace vectoriel de dimension n, pour tout n. Un exemple de graphe périodique est également traité. Ensuite, toujours pour le laplacien, on étudie plus précisément sur les arbres uniformément localement finis les valeurs propres dont l'espace propre est de dimension infini. Dans ce cas, il est montré que l'espace propre contient un sous-espace isomorphe à l'ensemble des suites réelles bornées. Une inégalité concernant le spectre est donnée dans le cas spécial où les arêtes sont de longueur un. Des exemples montrent que ces inclusions sont optimales. Dans le chapitre suivant, on étudie le comportement asymptotique des valeurs propres pour des opérateurs elliptiques d'ordre 2 quelconques sous des conditions de Kirchhoff dynamiques. Après réécriture du problème sous la forme d'un opérateur de Sturm-Liouville, on écrit le problème de façon matricielle. Puis on trouve une équation caractéristique dont les zéros correspondent aux valeurs propres. On en déduit une formule pour l'asymptotique des valeurs propres. Dans le dernier chapitre, on étudie la stabilité de solutions stationnaires pour certains problèmes de réaction-diffusion où le terme de non linéarité est polynomialAfter a quick presentation of usual notations for the graph theory, we study the set of harmonic functions on graphs, that is, the functions whose laplacian is zero. These functions form a vectorial space. On a uniformly locally finite tree, we shaw that this space has dimension one or infinity. When the graph has an infinite number of cycles, this result change and we describe some examples showing that there exists a graph on which the harmonic functions form a vectorial space of dimension n, for all n. We also treat the case of a particular periodic graph. Then, we study more precisely the eigenvalues of infinite dimension. In this case, the eigenspace contains a subspace isomorphic to the set of bounded sequences. An inequality concerning the spectral is given when edges length is equal to one. Examples show that these inclusions are optimal. We also study the asymptotic behavior of eigenvalues for elliptic operators under dynamical Kirchhoff node conditions. We write the problem as a Sturm-Liouville operator and we transform it in a matrix problem. Then we find a characteristic equation whose zeroes correspond to eigenvalues. We deduce a formula for the asymptotic behavior. In the last chapter, we study the stability of stationary solutions for some reaction-diffusion problem whose the non-linear term is polynomial
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Ponomarenko, Andrej. "Lösungsmethoden für Variationsungleichungen." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2003. http://dx.doi.org/10.18452/14841.
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Zusammenfassung Diese Arbeit ist ein Versuch, verschiedene klassische und neuere Methodender glatten bzw. nichtglatten Optimierung zu verallgemeinern und in ihrem Zusammenhang darzustellen. Als Hauptinstrument erweist sich dabei die sogenannte verallgemeinerte Kojima-Funktion. Neben reichlichen Beispielen setzen wir einen besonderen Akzent auf die Betrachtung von Variationsungleichungen, Komplementaritaetsaufgaben und der Standartaufgabeder mathematischen Programmierung. Unter natuerlichen Voraussetzungen an diese Probleme kann man u.a. Barriere-, Straf- und SQP-Typ-Methoden, die auf Newton-Verfahrenbasieren, aber auch Modelle, die sogenannte NCP-Funktionen benutzen, mittelsspezieller Stoerungen der Kojima-Funktion exakt modellieren. Daneben werdendurch explizite und natuerliche Wahl der Stoerungsparameter auch neue Methoden dieser Arten vorgeschlagen. Die Vorteile solcher Modellierungsind ueberzeugend vor allem wegen der direkt moeglichen (auf Stabilitaetseigenschaften der Kojima-Gleichung beruhendenden)Loesungsabschaetzungen und weil die entsprechenden Nullstellen ziemlich einfach als Loesungen bekannter Ersatzprobleme interpretiert werden koennen. Ein weiterer Aspekt der Arbeit besteht in der genaueren Untersuchungder "nichtglatten Faelle". Hier wird die Theorie von verschiedenen verallgemeinerten Ableitungen und dadurch entstehenden verallgemeinerten Newton-Verfahren, die im Buch "Nonsmooth Equations in Optimization" von B. Kummer und D. Klatte vorgeschlagen und untersucht wurde, intensiv benutzt. Entscheidend ist dabei, dass die benutzten verallgemeinerten Ableitungen auch praktisch angewandt werden koennen, da man sie exakt ausrechnen kann.This work attempts to generalize various classical and new methods of smooth or nonsmooth optimization and to show them in their interrelation. The main tool for doing this is the so-called generalized Kojima-function. In addition to numerous examples we specialy emphasize the consideration of variational inequalities, complementarity problems and the standard problem of mathematical programming. Under natural assumptions on these problems we can model e.g. barrier-, penalty-, and SQP-Type-methods basing on Newton methods, and also methods using the so-called NCP-function exactly by means of special perturbations of the Kojima-function. Furthermore, by the explicit and natural choice of the perturbation parameters new methods of these kinds are introduced. The benefit of such a modelling is obvious, first of all due to the direct solution estimation (basing on stability properties of the Kojima-equation) and because the corresponding zeros can easily be interpreted as solutions of known subproblems. A further aspect considered in this paper is the detailed investigation of "nonsmooth cases". The theory of various generalized derivatives and resulting generalized Newton methods, which is introduced and investigated in the book "Nonsmooth Equations in Optimization" of B. Kummer and D. Klatte, is intensely used here. The crucial point is the applicability of the used generalized derivatives in practice, since they can be calculated exactly.
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Karimou, Gazibo Mohamed. "Etudes mathématiques et numériques des problèmes paraboliques avec des conditions aux limites." Phd thesis, Université de Franche-Comté, 2013. http://tel.archives-ouvertes.fr/tel-00950759.
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Cette thèse est centrée autour de l'étude théorique et de l'analyse numérique des équations paraboliques non linéaires avec divers conditions aux limites. La première partie est consacrée aux équations paraboliques dégénérées mêlant des phénomènes non-linéaires de diffusion et de transport. Nous définissons des notions de solutions entropiques adaptées pour chacune des conditions aux limites (flux nul, Robin, Dirichlet). La difficulté principale dans l'étude de ces problèmes est due au manque de régularité du flux pariétal pour traiter les termes de bords. Ceci pose un problème pour la preuve d'unicité. Pour y remédier, nous tirons profit du fait que ces résultats de régularités sur le bord sont plus faciles à obtenir pour le problème stationnaire et particulièrement en dimension un d'espace. Ainsi par la méthode de comparaison "fort-faible" nous arrivons à déduire l'unicité avec le choix d'une fonction test non symétrique et en utilisant la théorie des semi-groupes non linéaires. L'existence de solution se démontre en deux étapes, combinant la méthode de régularisation parabolique et les approximations de Galerkin. Nous développons ensuite une approche directe en construisant des solutions approchées par un schéma de volumes finis implicite en temps. Dans les deux cas, on combine les estimations dans les espaces fonctionnels bien choisis avec des arguments de compacité faible ou forte et diverses astuces permettant de passer à la limite dans des termes non linéaires. Notamment, nous introduisons une nouvelle notion de solution appelée solution processus intégrale dont l'objectif, dans le cadre de notre étude, est de pallier à la difficulté de prouver la convergence vers une solution entropique d'un schéma volumes finis pour le problème de flux nul au bord. La deuxième partie de cette thèse traite d'un problème à frontière libre décrivant la propagation d'un front de combustion et l'évolution de la température dans un milieu hétérogène. Il s'agit d'un système d'équations couplées constitué de l'équation de la chaleur bidimensionnelle et d'une équation de type Hamilton-Jacobi. L'objectif de cette partie est de construire un schéma numérique pour ce problème en combinant des discrétisations du type éléments finis avec les différences finies. Ceci nous permet notamment de vérifier la convergence de la solution numérique vers une solution onde pour un temps long. Dans un premier temps, nous nous intéressons à l'étude d'un problème unidimensionnel. Très vite, nous nous heurtons à un problème de stabilité du schéma. Cela est dû au problème de prise en compte de la condition de Neumann au bord. Par une technique de changement d'inconnue et d'approximation nous remédions à ce problème. Ensuite, nous adaptons cette technique pour la résolution du problème bidimensionnel. A l'aide d'un changement de variables, nous obtenons un domaine fixe facile pour la discrétisation. La monotonie du schéma obtenu est prouvée sous une hypothèse supplémentaire de propagation monotone qui exige que la frontière libre se déplace dans les directions d'un cône prescrit à l'avance.
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Källberg, David. "Nonparametric Statistical Inference for Entropy-type Functionals." Doctoral thesis, Umeå universitet, Institutionen för matematik och matematisk statistik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-79976.
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In this thesis, we study statistical inference for entropy, divergence, and related functionals of one or two probability distributions. Asymptotic properties of particular nonparametric estimators of such functionals are investigated. We consider estimation from both independent and dependent observations. The thesis consists of an introductory survey of the subject and some related theory and four papers (A-D). In Paper A, we consider a general class of entropy-type functionals which includes, for example, integer order Rényi entropy and certain Bregman divergences. We propose U-statistic estimators of these functionals based on the coincident or epsilon-close vector observations in the corresponding independent and identically distributed samples. We prove some asymptotic properties of the estimators such as consistency and asymptotic normality. Applications of the obtained results related to entropy maximizing distributions, stochastic databases, and image matching are discussed. In Paper B, we provide some important generalizations of the results for continuous distributions in Paper A. The consistency of the estimators is obtained under weaker density assumptions. Moreover, we introduce a class of functionals of quadratic order, including both entropy and divergence, and prove normal limit results for the corresponding estimators which are valid even for densities of low smoothness. The asymptotic properties of a divergence-based two-sample test are also derived. In Paper C, we consider estimation of the quadratic Rényi entropy and some related functionals for the marginal distribution of a stationary m-dependent sequence. We investigate asymptotic properties of the U-statistic estimators for these functionals introduced in Papers A and B when they are based on a sample from such a sequence. We prove consistency, asymptotic normality, and Poisson convergence under mild assumptions for the stationary m-dependent sequence. Applications of the results to time-series databases and entropy-based testing for dependent samples are discussed. In Paper D, we further develop the approach for estimation of quadratic functionals with m-dependent observations introduced in Paper C. We consider quadratic functionals for one or two distributions. The consistency and rate of convergence of the corresponding U-statistic estimators are obtained under weak conditions on the stationary m-dependent sequences. Additionally, we propose estimators based on incomplete U-statistics and show their consistency properties under more general assumptions.
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Bouafia, Philippe. "Representation operators of metric and Euclidian charges." Phd thesis, Université Paris Sud - Paris XI, 2014. http://tel.archives-ouvertes.fr/tel-01015943.
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We study multiple valued functions with values in a Hilbert space. We introduce a possibledefinition of Sobolev spaces and the rightful notion of p energy. We prove the existence of pminimizers. Then we consider two-valued real functions of two variables which are stationarywith respect to both domain and range transformations. We prove their local Lipschitzcontinuity and use it to establish strong convergence in W1,2 to their unique blow-up at anypoint. We claim that the branch set of any such function consists of finitely many real analyticcurves meeting at nod points with equal angles. We also provide an example showing thatstationarity with respect to domain transformations only does not imply continuity.In a second part, we prove that there does not exist a uniformly continuous retractionfrom the space of continuous vector fields onto the subspace of vector fields whose divergencevanishes in the distributional sense. We then generalise this result using the concept of mcharges on any subset X _ Rn satisfying a mild geometric condition, there is no uniformlycontinuous representation operator for mcharges in X.
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Caubet, Fabien. "Détection d’un objet immergé dans un fluide." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3006/document.
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Cette thèse s’inscrit dans le domaine des mathématiques appelé optimisation de formes. Plus précisément, nous étudions ici un problème inverse de détection à l’aide du calcul de forme et de l’analyse asymptotique. L’objectif est de localiser un objet immergé dans un fluide visqueux, incompressible et stationnaire. Les questions principales qui ont motivé ce travail sont les suivantes :– peut-on détecter un objet immergé dans un fluide à partir d’une mesure effectuée à la surface ?– peut-on reconstruire numériquement cet objet, i.e. approcher sa position et sa forme, à partir de cette mesure ?– peut-on connaître le nombre d’objets présents dans le fluide en utilisant cette mesure ?Les résultats obtenus sont décrits dans les cinq chapitres de cette thèse :– le premier met en place un cadre mathématique pour démontrer l’existence des dérivées de forme d’ordre un et deux pour les problèmes de détection d’inclusions ;– le deuxième analyse le problème de détection à l’aide de l’optimisation géométrique de forme : un résultat d’identifiabilité est montré, le gradient de forme de plusieurs types de fonctionnelles de forme est caractérisé et l’instabilité de ce problème inverse est enfin démontrée ;– le chapitre 3 utilise nos résultats théoriques pour reconstruire numériquement des objets immergés dans un fluide à l’aide d’un algorithme de gradient de forme ;– le chapitre 4 analyse la localisation de petites inclusions dans un fluide à l’aide de l’optimisation topologique de forme : le gradient topologique d’une fonctionnelle de forme de Kohn-Vogelius est caractérisé ;– le dernier chapitre utilise cette dernière expression théorique pour déterminer numériquement le nombre et la localisation de petits obstacles immergés dans un fluide à l’aide d’un algorithme de gradient topologiqueThis dissertation takes place in the mathematic field called shape optimization. More precisely, we focus on a detecting inverse problem using shape calculus and asymptotic analysis. The aim is to localize an object immersed in a viscous, incompressible and stationary fluid. This work was motivated by the following main questions:– can we localize an obstacle immersed in a fluid from a boundary measurement?– can we reconstruct numerically this object, i.e. be close to its localization and its shape, from this measure?– can we know how many objects are included in the fluid using this measure?The results are described in the five chapters of the thesis:– the first one gives a mathematical framework in order to prove the existence of the shape derivatives oforder one and two in the frame of the detection of inclusions;– the second one analyzes the detection problem using geometric shape optimization: an identifiabilityresult is proved, the shape gradient of several shape functionals is characterized and the instability of thisinverse problem is proved;– the chapter 3 uses our theoretical results in order to reconstruct numerically some objets immersed in a fluid using a shape gradient algorithm;– the fourth chapter analyzes the detection of small inclusions in a fluid using the topological shape optimization : the topological gradient of a Kohn-Vogelius shape functional is characterized;– the last chapter uses this theoretical expression in order to determine numerically the number and the location of some small obstacles immersed in a fluid using a topological gradient algorithm
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Franceschi, Sandro. "Approche analytique pour le mouvement brownien réfléchi dans des cônes." Thesis, Tours, 2017. http://www.theses.fr/2017TOUR4046/document.
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Le mouvement Brownien réfléchi de manière oblique dans le quadrant, introduit par Harrison, Reiman, Varadhan et Williams dans les années 80, est un objet largement analysé dans la littérature probabiliste. Cette thèse, qui présente l’étude complète de la mesure invariante de ce processus dans tous les cônes du plan, a pour objectif plus global d’étendre au cadre continu une méthode analytique développée initialement pour les marches aléatoires dans le quart de plan par Fayolle, Iasnogorodski et Malyshev dans les années 70. Cette approche est basée sur des équations fonctionnelles, reliant des fonctions génératrices dans le cas discret et des transformées de Laplace dans le cas continu. Ces équations permettent de déterminer et de résoudre des problèmes frontière satisfaits par ces fonctions génératrices. Dans le cas récurrent, cela permet de calculer explicitement la mesure invariante du processus avec rebonds orthogonaux, dans le chapitre 2, et avec rebonds quelconques, dans le chapitre 3. Les transformées de Laplace des mesures invariantes sont prolongées analytiquement sur une surface de Riemann induite par le noyau de l’équation fonctionnelle. L’étude des singularités et l’application de méthodes du point col sur cette surface permettent de déterminer l’asymptotique complète de la mesure invariante selon toutes les directions dans le chapitre 4Obliquely reflected Brownian motion in the quadrant, introduced by Harrison, Reiman, Varadhan and Williams in the eighties, has been studied a lot in the probabilistic literature. This thesis, which presents the complete study of the invariant measure of this process in all the cones of the plan, has for overall aim to extend to the continuous framework an analytic method initially developped for random walks in the quarter plane by Fayolle, Iasnogorodski and Malyshev in the seventies. This approach is based on functional equations which link generating functions in the discrete case and Laplace transform in the continuous case. These equations allow to determine and to solve boundary value problems satisfied by these generating functions. In the recurrent case, it permits to compute explicitly the invariant measure of the process with orthogonal reflexions, in the chapter 2, and with any reflexions, in the chapter 3. The Laplace transform of the invariant measure is analytically extended to a Riemann surface induced by the kernel of the functional equation. The study of singularities and the use of saddle point methods on this surface allows to determine the full asymptotics of the invariant measure along every directions in the chapter 4
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Brenot, Dominique. "Transmission du son à l'intérieur d'une structure axisymétrique." Paris 6, 1986. http://www.theses.fr/1986PA066022.
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Problème de la transmission du son sur l'axe d'une structure élastique fermée à symétrie de révolution. Problème de Neumann, associé à la pression acoustique par la méthode de la phase stationnaire et problème de structure par une méthode d'éléments finis.
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Feng, Yuehong. "Stabilité de solutions régulières pour des systèmes d'Euler-Maxwell et de Navier-Stokes-Maxwell compressibles." Thesis, Clermont-Ferrand 2, 2014. http://www.theses.fr/2014CLF22484/document.
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Cette thèse est essentiellement composée de deux parties traitant des problèmes de Cauchy ou des problèmes périodiques. Dans la première partie, on étudie la stabilité de solutions régulières au voisinage d'états d'équilibre non constants pour un système d'Euler-Maxwell isentropique compressible bipolaire. Par des estimations d'énergie classiques et un argument de récurrence sur l'ordre des dérivées des solutions, on montre l'existence globale et l'unicité des solutions régulières du système lorsque les données initiales sont proches des états d'équilibre. On obtient aussi le comportement asymptotique des solutions quand le temps tend vers l'infini. Dans la deuxième partie, on considère la stabilité en temps long des solutions régulières de systèmes d'Euler-Maxwell et de Navier-Stokes-Maxwell compressibles dans le cas non isentropique lorsque les états d'équilibre sont constants. Grâce à des choix convenables de symétriseurs des systèmes et à des estimations d'énergie, on montre l'existence globale et l'unicité des solutions régulières des systèmes avec données initiales petites. De plus, par le principe de Duhamel et l'outil d'analyse de Fourier, on obtient des taux de décroissance des solutions quand le temps tend vers l'infiniThis thesis is essentially composed of two parts dealing with Cauchy problems and periodic problems. In the first part, we study the stability of smooth solutions near non constant equilibrium states for a two-fluid isentropic compressible Euler-Maxwell system.By classical energy estimates together with an induction argument on the order of the derivatives of solutions, we prove the existence and uniqueness of global solutions to the system when the given initial data are near the equilibrium states. We also obtain the asymptotic behavior of solutions when the time goes to infinity. In the second part, we consider the long time stability of the global smooth solutions for compressible Euler-Maxwell and Navier-Stokes-Maxwell systems in non isentropic case when the equilibrium solutions are constants. With the help of suitable choices of symmetrizers and energy estimates, we prove the existence and uniqueness of global solutions to the systems with given small initial data. Furthermore, using the Duhamel principle and the Fourier analysis tool, we obtain the decay rates of smooth solutions as the time goes to infinity
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SALDI, SARA. "Some nonlocal nonlinear problems in the stationary and evolutionary case." Doctoral thesis, 2017. http://hdl.handle.net/2158/1088217.
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Nel lavoro di tesi è stato affrontato lo studio di problemi non lineari e non locali, sia nel caso stazionario sia nel caso evolutivo. Nel primo capitolo abbiamo affrontato un problema agli autovalori con condizioni al bordo di Dirichlet omogenee, in un aperto limitato di R^n con frontiera Lipschitziana,
in cui è presente un operatore integro-differenziale non locale. Nel secondo capitolo abbiamo stabilito esistenza e molteplicità di soluzioni non negative e non banali di un problema di Kirchhoff stazionario agli autovalori per un generico operatore integro-differenziale non locale. Il modello preso in considerazione dipende da un parametro e presenta due nonlinearità superlineari, di cui una può essere critica o supercritica. Nel terzo capitolo ci siamo occupati di stabilità asintotica globale e locale per sistemi di tipo Kirchhoff con termini di smorzamento non lineare. Infine, nel quarto capitolo abbiamo studiato l'esistenza di soluzioni non negative e non banali di sistemi di tipo Schrodinger-Hardy, in cui figurano due p-Laplaciani frazionari differenti.
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Evangelista, David. "Stationary Mean-Field Games with Congestion." Diss., 2019. http://hdl.handle.net/10754/655679.
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Mean-field games (MFG) are models of large populations of rational agents who seek to optimize an objective function that takes into account their state variables and the distribution of the state variable of the remaining agents. MFG with congestion model problems where the agents’ motion is hampered in high-density regions.
First, we study radial solutions for first- and second-order stationary MFG with congestion on Rd. The radial case, which is one of the simplest non one-dimensional MFG, is relatively tractable. As we observe, the Fokker-Planck equation is integrable with respect to one of the unknowns. Consequently, we obtain a single equation substituting this solution into the Hamilton-Jacobi equation. For the first-order case, we derive explicit formulas; for the elliptic case, we study a variational formulation of the resulting equation. For the first case, we use our approach to compute numerical approximations to the solutions of the corresponding MFG systems.
Next, we consider second-order stationary MFG with congestion and prove the existence of stationary solutions. Because moving in congested areas is difficult, agents prefer to move in non-congested areas. As a consequence, the model becomes singular near the zero density. The existence of stationary solutions was previously obtained for MFG with quadratic Hamiltonians thanks to a very particular identity. Here, we develop robust estimates that give the existence of a solution for general subquadratic Hamiltonians.
Additionally, we study first-order stationary MFG with congestion with quadratic or power-like Hamiltonians. Using explicit examples, we illustrate two key difficulties: the lack of classical solutions and the existence of areas with vanishing densities. Our
main contribution is a new variational formulation for MFG with congestion. With this formulation, we prove the existence and uniqueness of solutions. Finally, we devise a discretization that is combined with optimization algorithms to numerically solve various MFG with congestion.
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Liu, Xinwei, and Jie Sun. "Generalized Stationary Points and an Interior Point Method for MPEC." 2003. http://hdl.handle.net/1721.1/3701.
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Mathematical program with equilibrium constraints (MPEC)has extensive applications in practical areas such as traffic control, engineering design, and economic modeling. Some generalized stationary points of MPEC are studied to better describe the limiting points produced by interior point methods for MPEC.A primal-dual interior point method is then proposed, which solves a sequence of relaxed barrier problems derived from MPEC. Global convergence results are deduced without assuming strict complementarity or linear independence constraint qualification. Under very general assumptions, the algorithm can always find some point with strong or weak stationarity. In particular, it is shown that every limiting point of the generated sequence is a piece-wise stationary point of MPEC if the penalty parameter of the merit function is bounded. Otherwise, a certain point with weak stationarity can be obtained. Preliminary numerical results are satisfactory, which include a case analyzed by Leyffer for which the penalty interior point algorithm failed to find a stationary solution.Singapore-MIT Alliance (SMA)
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"On merit functions, error bounds, minimizing and stationary sequences for nonsmooth variational inequality problems." Thesis, 2005. http://library.cuhk.edu.hk/record=b6074106.
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First, we study the associated regularized gap functions and the D-gap functions and compute their Clarke-Rockafellar directional derivatives and the Clarke generalized gradients. Second, using these tools and extending the works of Fukushima and Pang (who studied the case when F is smooth), we present results on the relationship between minimizing sequences and stationary sequences of the D-gap functions, regardless the existence of solutions of (VIP). Finally, as another application, we show that, under the strongly monotonicity assumption, the regularized gap functions have fractional exponent error bounds, and thereby we provide an algorithm of Armijo type to solve the (VIP).In this thesis, we investigate a nonsmooth variational inequality problem (VIP) defined by a locally Lipschitz function F which is not necessarily differentiable or monotone on its domain which is a closed convex set in an Euclidean space.
Tan Lulin.
"December 2005."
Adviser: Kung Fu Ng.
Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6444.
Thesis (Ph.D.)--Chinese University of Hong Kong, 2005.
Includes bibliographical references (p. 79-84) and index.
Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.
Abstracts in English and Chinese.
School code: 1307.
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Traytak, S. D., and D. S. Grebenkov. "Semi-analytical solutions of boundary value problems for the stationary diffusion equation in three-dimensional canonical domains." 2017. https://ul.qucosa.de/id/qucosa%3A31603.
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We present the generalized method of separation of variables (GMSV) to solve boundary value problems for the stationary diffusion equation in three-dimensional canonical domains (e.g., parallelepipeds, cylinders, spheres, spheroids, ..., and also their combinations).
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TRONCI, EDOARDO MARIA. "How to escape nonconvex regions efficiently in large scale optimization problems." Doctoral thesis, 2022. http://hdl.handle.net/11573/1635338.
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Solving large scale optimization problems, such as neural networks training, can present many challenges. Among others, the proliferation of useless stationary points, that is points where the objective function value is quite far from that of a global minimum, can pose a serious drawback for the optimization algorithm used, which is attracted by them and therefore results inefficient. In this dissertation, we propose two algorithmic schemes along the following lines. First, extending the result proposed in [1] for shallow networks, that is networks with only one hidden layer, we propose a mathematical characterization of a class of such stationary points that arise in deep multilayer neural networks training, that is networks with more than one hidden layer. Availing such a description, we are able to define an incremental training approach that avoids getting stuck in the region of attraction of these undesirable stationary points. Then, exploiting the main properties of the nonmonotone truncated Newton’s method proposed in [2], we attempt to grasp the benefits of using second-order information by giving a preliminary numerical evidence of the potential of following directions of negative curvature during neural networks training in order to guarantee the skill of the optimization algorithm in escaping regions where the objective function is nonconvex.
References:
[1] Fukumizu, K., & Amari, S. I. (2000). Local minima and plateaus in hierarchical structures of multilayer perceptrons. Neural networks, 13(3), 317-327.
[2] Fasano, G., & Lucidi, S. (2009). A nonmonotone truncated Newton–Krylov method exploiting negative curvature directions, for large scale unconstrained optimization. Optimization Letters, 3(4), 521-535.
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Hsu, Yuan-Hsiung, and 徐遠雄. "Application of a Non-Orthogonal Collocated Finite-Volume Algorithm to Convective Heat Transfer Problems in Horizontal Stationary/Rotating Annuli." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/33085117484304160622.
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Anoop, K. P. "Truncated Data Problems In Helical Cone-Beam Tomography." Thesis, 2008. http://hdl.handle.net/2005/766.
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This report delves into two of the major truncated data problems in helical cone-beam tomography: Axial truncation and Lateral truncation. The problem of axial truncation, also classically known as the Long Object problem, was a major challenge in the development of helical scan tomography. Generalization of the Feldkamp method (FDK) for circular scan to the helical scan trajectory was known to give reasonable solutions to the problem. The FDK methods are approximate in nature and hence provide only approximate solution to the long object problem. Recently, many methods which provide exact solution to this problem have been developed the major breakthrough being the Katsevich’s algorithm which is exact, efficient and also requires lesser detector area compared to Feldkamp methods. The first part of the report deals with the implementation strategies for methods capable of handling axial truncation. Here, we specifically look at the exact and efficient Katsevich’s solution to long object problem and the class of approximate solutions provided by the generalized FDK formulae.
The later half of the report looks at the lateral truncation problem and suggests new methods to handle such truncation in helical scan CT. Simulation results for reconstruction with laterally truncated projection data, assuming it to be complete, gives severe artifacts which even penetrates into the field of view (FOV). A row-by-row data completion approach using Linear Prediction is introduced for helical scan truncated data. An extension/improvement of this technique known as Windowed Linear Prediction approach is introduced. Efficacy of both these techniques are shown using simulation with standard phantoms. Various image quality measures for the resulting reconstructed images are used to evaluate the performance of the proposed methods against an already existing technique.
Motivated by a study of the autocorrelation and partial autocorrelation functions of the projection data the use of a non-stationary linear model, the ARIMA model, is proposed for data completion. The new model is first validated in the 2D truncated data situation. Also a method of incorporating the parallel beam data consistency condition into this new method is considered. Performance evaluation of the new method with consistency condition shows that it can outperform the existing techniques. Simulation experiments show the efficacy of the ARIMA model for data completion in 2D as well as 3D truncated data scenario. The model is shown to work well for the laterally truncated helical cone-beam case.
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Ye, Ting-Gu, and 葉庭谷. "Application of Non-stationary Time Series Data to Environmental Engineering Problems - from Physically based Gambler''s ruin (GR) Model to Time-Frequency Analysis (TFA)." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/3n37x6.
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碩士國立臺灣大學
土木工程學研究所
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Part I: Water Quality Risk Analysis The Gambler’s ruin model has been employed to estimate the probability of reaching the designated sediment capacity such as the pre-established water quality standard or maximum sediment carrying capacity in reservoirs with different flow conditions. However, this theoretical model has a stationary probability assumption used to reduce mathematical complexity. In this study, we develop a non-stationary Gambler’s ruin model by using the Monte Carlo simulation method. Finally we use the daily water level data of the Xia Yun hydrologic station to predict the effective risk of reaching the maximum capacity of the water treatment plant in the Shihmen Reservoir in 2008. Compared with previous work, this non-stationary model could obtain more accurate probability, which can be proved using measured daily concentration data of the Shihmen Reservoir. Part II: Time Frequency Analysis Extreme events occur more and more frequently due to climate change. Recently the dengue fever is a pressing issue of southern Taiwan, and the dengue fever might have characteristic temporal scales that can be further identified. Some researchers hypothesized that the dengue fever events might have linkage with climate change. In this study we propose to use the time-frequency analysis to observe time series data of the dengue fever, and hydrologic and meteorological variables. In addition, we also compare and discuss the analysis results from three time-frequency methods, the Hilbert Huang transform (HHT), the Wavelet transform (WT) and the short time Fourier transform (SFFT). A more suitable time-frequency analysis method will be identified and selected to further analyze relevant time series data pertinent to the aforementioned issue. The most influential time scales of hydrologic and meteorological variables associated with dengue fever can be identified. Finally the linkage between hydrologic/meteorological factors and the number of dengue fever incidences can be established.
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GUI, SHAO-GIN, and 桂少卿. "A transfer-function approach to the stationary linear quadratic gaussian (LQG) control problem." Thesis, 1987. http://ndltd.ncl.edu.tw/handle/28223245423702112596.
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Reinl, Heidi [Verfasser]. "Stationäre Drogentherapie im Spiegel professioneller Arbeitskonzepte : eine sozialpädagogische Fallstudie / Heidi Reinl." 2008. http://d-nb.info/989062309/34.
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Tang, Lan 1980. "Random homogenization of p-Laplacian with obstacles on perforated domain and related topics." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3455.
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