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Tesi sul tema "Finite model theory"
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1
Bello, Aguirre Ricardo Isaac. "Model theory of finite and pseudofinite rings." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/15771/.
Testo completoAbstract (sommario):
The model theory of finite and pseudofinite fields as well as the model theory of finite and pseudofinite groups have been and are thoroughly studied. A close relation has been found between algebraic and model theoretic properties of pseudofinite fields and psedudofinite groups. In this thesis we present results contributing to the beginning of the study of model theory of finite and pseudofinite rings. In particular we classify the theory of ultraproducts of finite residue rings in the context of generalised stability theory. We give sufficient and necessary conditions for the theory of such ultraproducts to be NIP, simple, NTP2 but not simple nor NIP, or TP2 . Further, we show that for any fixed positive l in N the class of finite residue rings {Zp=p^l Zp : p in P} forms an l-dimensional asymptotic class. We discuss related classes of finite residue rings in the context of R-multidimensional asymptotic classes. Finally we present a classification of simple and semisimple (in the algebraic sense) pseudofinite rings, we study NTP2 classes of J-semisimple rings and we discuss NIP classes of finite rings and ultraproducts of these NIP classes.
2
Block, Max. "Undecidability of finite satisfiability and characterization of NP in finite model theory." Thesis, Uppsala universitet, Algebra och geometri, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-254570.
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3
Gate, James Simon. "Applications of finite model theory : optimisation problems, hybrid modal logics and games." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/7015/.
Testo completoAbstract (sommario):
There exists an interesting relationships between two seemingly distinct fields: logic from the field of Model Theory, which deals with the truth of statements about discrete structures; and Computational Complexity, which deals with the classification of problems by how much of a particular computer resource is required in order to compute a solution. This relationship is known as Descriptive Complexity and it is the primary application of the tools from Model Theory when they are restricted to the finite; this restriction is commonly called Finite Model Theory. In this thesis, we investigate the extension of the results of Descriptive Complexity from classes of decision problems to classes of optimisation problems. When dealing with decision problems the natural mapping from true and false in logic to yes and no instances of a problem is used but when dealing with optimisation problems, other features of a logic need to be used. We investigate what these features are and provide results in the form of logical frameworks that can be used for describing optimisation problems in particular classes, building on the existing research into this area. Another application of Finite Model Theory that this thesis investigates is the relative expressiveness of various fragments of an extension of modal logic called hybrid modal logic. This is achieved through taking the Ehrenfeucht-Fraïssé game from Model Theory and modifying it so that it can be applied to hybrid modal logic. Then, by developing winning strategies for the players in the game, results are obtained that show strict hierarchies of expressiveness for fragments of hybrid modal logic that are generated by varying the quantifier depth and the number of proposition and nominal symbols available.
4
Ryten, Mark Jonathan. "Model theory of finite difference fields and simple groups." Thesis, University of Leeds, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441226.
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5
Hayashi, Masahito. "Asymptotic estimation theory for a finite dimensional pure state model." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181932.
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6
Morgan, Samuel Alexander. "A gapless theory of Bose-Einstein condensation in dilute gases at finite temperature." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302178.
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7
Lin, Dong. "Model-based cluster analysis using Bayesian techniques." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2008. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
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8
Bhattacharyya, Anirban. "Application of effective field theory to density functional theory for finite systems." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1124116299.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xv, 210 p.; also includes graphics (some col.). Includes bibliographical references (p. 205-210). Available online via OhioLINK's ETD Center
9
Manikas, Vasileios. "A Bayesian Finite Mixture Model for Network-Telecommunication Data." Thesis, Stockholms universitet, Statistiska institutionen, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-146039.
Testo completoAbstract (sommario):
A data modeling procedure called Mixture model, is introduced beneficial to the characteristics of our data. Mixture models have been proved flexible and easy to use, a situation which can be confirmed from the majority of papers and books which have been published the last twenty years. The models are estimated using a Bayesian inference through an efficient Markov Chain Monte Carlo (MCMC) algorithm, known as Gibbs Sampling. The focus of the paper is on models for network-telecommunication lab data (not time dependent data) and on the valid predictions we can accomplish. We categorize our variables (based on their distribution) in three cases, a mixture of Normal distributions with known allocation, a mixture of Negative Binomial Distributions with known allocations and a mixture of Normal distributions with unknown allocation.
10
Groenewald, Hendrikus Wilhelm. "A non-commutative walecka model as an effective theory for interacting nucleons of finite size." Thesis, Stellenbosch : Stellenbosch University, 2012. http://hdl.handle.net/10019.1/20255.
Testo completoAbstract (sommario):
Thesis (MSc)--Stellenbosch University, 2012.<br>ENGLISH ABSTRACT: The nite size of nucleons should play an important role in the description of high density nuclear
matter as found in astro-physical objects. Yet we see that the Walecka model, which is generally
used to describe these systems, treats the nucleons as point particles. Here we argue that a
non-commutative version of the Walecka model may be a consistent and appropriate framework
to describe nite nucleon size e ects. In this framework the length scale introduced through
the non-commutative parameter plays the role of the nite nucleon size. To investigate the
consequences of this description, the equations of motion and energy-momentum tensor for the
non-commutative Walecka model are derived. We also derived an expression for the total energy
of the system, as a function of the non-commutative parameter, in a spatially non-uniform matter
approximation. The non-commutative parameter, as a variable dependent on the dynamics of
the system, remains to be solved self-consistently.<br>AFRIKAANSE OPSOMMING: Die eindige grootte van nukleone moet 'n belangrike rol speel in die beskrywing van ho e-digtheid
kern materie soos gevind in astro- siese voorwerpe. Tog sien ons dat die Walecka model, wat in
die algemeen gebruik word om hierdie stelsels te beskryf, die nukleone as punt deeltjies hanteer.
Ons redeneer dus dat 'n nie-kommutatiewe weergawe van die Walecka model 'n konsistente en
gepaste raamwerk is om die e ekte van eindige nukleon grootte te beskryf. In hierdie raamwerk
speel die lengte-skaal wat ingevoer word deur die nie-kommutatiewe parameter die rol van eindige
grootte vir nukleone. Om die gevolge van hierdie beskrywing te ondersoek, word die vergelykings
van beweging en die energie-momentum tensor afgelei vir die nie-kommutatiewe Walecka model.
Ons het ook 'n uitdrukking vir die totale energie van die stelsel, as 'n funksie van die niekommutatiewe
parameter, afgelei in 'n ruimtelik nie-uniforme materie benadering. Die niekommutatiewe
parameter, as 'n veranderlike afhanklik van die dinamika van die stelsel, bly
steeds om self-konsistent opgelos te word.
11
Wang, Yang. "Use of finite random graphs to model packet radio networks." Ohio : Ohio University, 1990. http://www.ohiolink.edu/etd/view.cgi?ohiou1183474696.
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12
Korzec, Tomasz. "Precise determination of universal finite volume observables in the Gross-Neveu model." Doctoral thesis, [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985491590.
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13
MIRJALILI, Mojtaba. "Numerical Analysis of a Large-Scale Levee on Soft Soil Deposits Using Two-Phase Finite Deformation Theory." 京都大学 (Kyoto University), 2010. http://hdl.handle.net/2433/126785.
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14
Miguel, Escudero López José. "Traffic-induced vibrations on a two span composite railway bridge : Comparison of theory and measurements." Thesis, KTH, Bro- och stålbyggnad, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36360.
Testo completoAbstract (sommario):
The economic and technologic development experienced by the society in the last decades has caused the demand of a new type of faster and more comfortable transport. This type of demand has been covered by the air transport, the road transport and the railway transport. This situation where the society demands an improvement in her quality of life is the best situation for the birth of the high speed trains. Different studies carried out in the transport field have demonstrated that for distances between four hundred and one thousand of kilometres, the high speed trains provide a lower travelling times than the rest of the transports. These types of high speed trains have increased the axle loads and the average speeds, thus generally a dynamic analysis is required by the ERRI in all the railway bridges when the train speed is higher than 200 Km/h. Besides, when the train speed is going to be higher than 200 Km/h, the vibrations induced in the bridge can reduce the service life of the vehicles and structure, and generally, this fact leads to become the dynamic effect in the principal factor to take into account in order to design the structure. Therefore, an important knowledge in railway bridges dynamic is required to not to oversize the structures with the consequent economic cost. The purpose of this thesis is to study the possibility of accurately predicting the dynamic response of an existing railway bridge, subjected to the high speed train Gröna Tåget, implementing a simplified 2D finite element model with the aid of the program Abaqus. The bridge chosen is the Lögdeälv Bridge, a two spans composite bridge, located along the Bothnia Line (the new Swedish high-speed line), between the localities of Nordmaling and Rundvik. The measured eigenfrequencies due to bending modes of vibration are used for updating the model and then, these frequencies and the accelerations measured are used to compare and validate the different 2D updated models. The parameters used to update the models are; the damping coefficient of the structure, the mass and the stiffness of the bridge, and the supports stiffness. Finally it is concluded that the best model is achieved when the rotational support stiffness is modified in the two extremes supporters of the bridge.
15
Mascarenhas, Helena. "Convolution type operators on cones and asymptotic spectral theory." Doctoral thesis, [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=970638809.
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16
Ahlman, Ove. "To infinity and back : Logical limit laws and almost sure theories." Licentiate thesis, Uppsala universitet, Algebra och geometri, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-223166.
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17
Sheikh, Nadeem A. "Comparison of constitutive relationships based on kinetic theory of granular gas for three dimensional vibrofluidized beds." Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/7881.
Testo completoAbstract (sommario):
Granular materials exist in many forms in nature ranging from space debris to sand dunes and from breakfast cereals to pharmaceutical tablets. They can behave like a solid or a viscous fluid or a gas. The gas-like nature of granular materials in rapid flows allows the use of models based on kinetic theory thus revealing in depth complex physics and phenomena. However unlike conventional fluids here the energy balance requires additional dissipation terms as a consequence of inelasticity. The complexity of their interaction and diversity in application has led to numerous studies using experimental methods and numerical simulations in order to determine the most appropriate constitutive relationships for granular gases. With large dissipation the form of the constitutive relationship becomes particularly important, especially in the presence of non-equipartition and anisotropy. This thesis is focused on constitutive models of simple granular flows. A vibrated bed is often used as an idealisation of granular flows, providing a convenient approximation to the simplest type of flow: binary and instantaneous collisions with no rotations. Using finite element method (FE) based COMSOL modules we solve conservation of mass, momentum and energy resulting from granular kinetic theory in axi-symmetric form to generate time and spatial resolved solutions of packing fraction, velocity and granular temperature and compare the predictions to numerical simulation and experiment. At first we show the comparison for two closure sets, one based on a simple near elastic approach while the second based on revised Enskog theory for dense inelastic flows. The results for the second approach show good agreement with the results of previously validated near elastic models and experimental results. The observed differences between the two closure sets are small except for the observation of temperature upturn in a dilute region of the cell away from base. One cause of this is the presence of additional constitutive terms in the balance equations and are a consequence of inelasticity. The models also consider time varying effects at low frequency of excitation. These solutions show existence of wave-like effects in the cell with associated temperature upturn within the hydrodynamic applicability region. Presence of instantaneous cyclic rolling is also seen in both approaches. Evidence from MD simulations and experiments qualitatively support the findings of hydrodynamic models in phase resolved as well as time average behaviour. Subsequently, the frequency of vibration was varied to unlink the wave motion from the bulk temperature. Lack of agreement between experiment and the model predictions are shown to be due to lack of separation of time scale between the grain-base interaction and the base frequency. A sharp decrease of heat flux is measured showing that the energy input is frequency dependent. Analysis of the bulk behaviour shows that at high frequency, hard sphere based models are able to capture the steady state behaviour reasonably well. Further investigations that modulate the driving with a low frequency amplitude change revealed the dynamic nature of flow with the low frequency component. No significant influence of high frequency signal is noted except the reduction of base heat flux. Independent analysis of bulk behaviour for modulated wave excitation using MD simulations and hydrodynamic models showed wave motion in a pattern similar to non-modulated low frequency vibration. A one-dimensional inviscid model was used to determine the underlying scaling relationships for near elastic granular flows. A form of non-dimensionalisation predicts scaling behaviour for the granular flow. The predictions show good results for the dilute flows using hard sphere MD simulations. Results from MD simulations confirm dilute limit scaling of base temperature, packing fractions and heat flux coefficients. At higher inelasticity and loading condition the model fails to capture the real physics suggesting the need for a more accurate model. This simplified model does, however, set the basis for describing the main scalings for vibrofluidized granular beds, and in the future we anticipate that effects of further inelasticity and enhanced density could be incorporated.
18
Udoyen, Nsikan. "Information Modeling for Intent-based Retrieval of Parametric Finite Element Analysis Models." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14084.
Testo completoAbstract (sommario):
Adaptive reuse of parametric finite element analysis (FEA) models is a common form of reuse that involves integrating new information into an archived FEA model to apply it towards a new similar physical problem. Adaptive reuse of archived FEA models is often motivated by the need to assess the impact of minor improvements to component-based designs such as addition of new structural components, or the need to assess new failure modes that arise when a device is redesigned for new operating environments or loading conditions. Successful adaptive reuse of FEA models involves reference to supporting documents that capture the formulation of the model to determine what new information can be integrated and how. However, FEA models and supporting documents are not stored in formats that are semantically rich enough to support automated inference of their relevance to a modelers needs. The modelers inability to precisely describe information needs and execute queries based on such requirements results in inefficient queries and time spent manually assessing irrelevant models. The central research question in this research is thus how do we incorporate a modelers intent into automated retrieval of FEA models for adaptive reuse?
An automated retrieval method to support adaptive reuse of parametric FEA models has been developed in the research documented in this thesis. The method consists of a classification-based retrieval method based on ALE subsumption hierarchies that classify models using semantically rich description logic representations of physical problem structure and a reusability-based ranking method. Conceptual data models have been developed for the representations that support both retrieval and ranking of archived FEA models. The method is validated using representations of FEA models of several classes of electronic chip packages. Experimental results indicate that the properties of the representation methods support effective automation of retrieval functions for FEA models of component-based designs.
19
NAKANO, MASAKI, AKIRA ASAOKA, and TOSHIHIRO NODA. "SOIL-WATER COUPLED FINITE DEFORMATION ANALYSIS BASED ON A RATE-TYPE EQUATION OF MOTION INCORPORATING THE SYS CAM-CLAY MODEL." 地盤工学会, 2008. http://hdl.handle.net/2237/20062.
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20
Rossi, Marco, Thomas Wallmersperger, Jorge Alejandro Ramirez, and Paola Nardinocchi. "jz Thermodynamically consistent electro-chemo-mechanical model for polymer membranes." SPIE, 2018. https://tud.qucosa.de/id/qucosa%3A35160.
Testo completoAbstract (sommario):
Nafion membranes, are polymeric thin films widely employed in micro-batteries and fuel cells. These devices are expected to play a key role in the next generation energy systems for use in vehicles as a replacement to combustion engines. In fact, a minimum environmental impact is guaranteed by reduced carbon dioxide emissions. It is usually complicated to investigate the behavior of thin membranes through experiments. Therefore, numerical simulations are carried out in order to enable a better understanding of the phenomena and of the multi-field couplings occurring in polymeric membranes.
A continuum-based, three-dimensional and electro-chemo-mechanical (ECM) model for a hydrated polymer membrane is presented. Different effects are taken into account: (i) mechanics, (ii) water uptake, (iii) ion transport, and (iv) electrostatics. The dissipation inequality drives the choice of the suitable constitutive equations of the multi-physics theory. In the mechanical field, an additive decomposition of the deformation gradient in (i) a distortion part, related to the ion motion, and (ii) an elastic part, is assumed. The multi-field model is numerically solved within the finite element framework. Time-dependent simulations are performed by using the commercial tool COMSOL Multiphysics. Furthermore, two closed form solutions are obtained by using (i) a one-dimensional reduced model and (ii) an approach based on the bar theory with an electro-chemical distortion field.
21
Eickmeyer, Kord. "Randomness in complexity theory and logics." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16364.
Testo completoAbstract (sommario):
Die vorliegende Dissertation besteht aus zwei Teilen, deren gemeinsames Thema in der Frage besteht, wie mächtig Zufall als Berechnungsressource ist. Im ersten Teil beschäftigen wir uns mit zufälligen Strukturen, die -- mit hoher Wahrscheinlichkeit -- Eigenschaften haben können, die von Computeralgorithmen genutzt werden können. In zwei konkreten Fällen geben wir bis dahin unbekannte deterministische Konstruktionen solcher Strukturen: Wir derandomisieren eine randomisierte Reduktion von Alekhnovich und Razborov, indem wir bestimmte unbalancierte bipartite Expandergraphen konstruieren, und wir geben eine Reduktion von einem Problem über bipartite Graphen auf das Problem, den minmax-Wert in Dreipersonenspielen zu berechnen. Im zweiten Teil untersuchen wir die Ausdrucksstärke verschiedener Logiken, wenn sie durch zufällige Relationssymbole angereichert werden. Unser Ziel ist es, Techniken aus der deskriptiven Komplexitätstheorie für die Untersuchung randomisierter Komplexitätsklassen nutzbar zu machen, und tatsächlich können wir zeigen, dass unsere randomisierten Logiken randomisierte Komlexitätsklassen einfangen, die in der Komplexitätstheorie untersucht werden. Unter Benutzung starker Ergebnisse über die Logik erster Stufe und die Berechnungsstärke von Schaltkreisen beschränkter Tiefe geben wir sowohl positive als auch negative Derandomisierungsergebnisse für unsere Logiken. Auf der negativen Seite zeigen wir, dass randomisierte erststufige Logik gegenüber normaler erststufiger Logik an Ausdrucksstärke gewinnt, sogar auf Strukturen mit einer eingebauten Additionsrelation. Außerdem ist sie nicht auf geordneten Strukturen in monadischer zweitstufiger Logik enthalten, und auch nicht in infinitärer Zähllogik auf beliebigen Strukturen. Auf der positiven Seite zeigen wir, dass randomisierte erststufige Logik auf Strukturen mit einem unären Vokabular derandomisiert werden kann und auf additiven Strukturen in monadischer Logik zweiter Stufe enthalten ist.<br>This thesis is comprised of two main parts whose common theme is the question of how powerful randomness as a computational resource is. In the first part we deal with random structures which possess -- with high probability -- properties than can be exploited by computer algorithms. We then give two new deterministic constructions for such structures: We derandomise a randomised reduction due to Alekhnovich and Razborov by constructing certain unbalanced bipartite expander graphs, and we give a reduction from a problem concerning bipartite graphs to the problem of computing the minmax-value in three-player games. In the second part we study the expressive power of various logics when they are enriched by random relation symbols. Our goal is to bridge techniques from descriptive complexity with the study of randomised complexity classes, and indeed we show that our randomised logics do capture complexity classes under study in complexity theory. Using strong results on the expressive power of first-order logic and the computational power of bounded-depth circuits, we give both positive and negative derandomisation results for our logics. On the negative side, we show that randomised first-order logic gains expressive power over standard first-order logic even on structures with a built-in addition relation. Furthermore, it is not contained in monadic second-order logic on ordered structures, nor in infinitary counting logic on arbitrary structures. On the positive side, we show that randomised first-order logic can be derandomised on structures with a unary vocabulary and is contained in monadic second-order logic on additive structures.
22
Vallejos, Augusto, Shammely Ayala, and Roman Arciniega. "Improved First Order Formulation for Buckling Analysis of Functionally Graded Beams." Institute of Electrical and Electronics Engineers Inc, 2020. http://hdl.handle.net/10757/656419.
Testo completoAbstract (sommario):
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado.<br>In this research, an improved first order formulation is presented to study the critical buckling load in functionally graded beams. The formulation has five independent variables in comparison with the Timoshenko theory that has three. The Trefftz criterion is utilized with incremental and fundamental states to define the stability analysis. Virtual work statements are derived for the finite element model where the field variables are interpolated by Lagrange polynomials. The numerical results are compared and verified with other formulations found in literature. Parametric studies are also carried out for buckling behavior due to different slenderness ratios, power-law indices and boundary conditions. Applications of the model to functionally graded materials show the validity of the present approach.
23
Grijalva, Sebastian. "Boundary effects in quantum spin chains and Finite Size Effects in the Toroidal Correlated Percolation model." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP093.
Testo completoAbstract (sommario):
Cette thèse est divisée en deux parties : la première présente un modèle statistique en deux dimensions de percolation corrélée sur un réseau toroïdal. Nous présentons un protocole pour construire des surfaces corrélées à longue portée sur la base de surfaces gaussiennes fractionnaires, puis nous relions les ensembles de niveaux à une famille de modèles de percolation corrélés. Les clusters émergents sont ensuite étudiés numériquement, et nous testons leur symétrie conforme en vérifiant que les corrections de taille finie de connectivité à deux points suivent les prédictions de la théorie des champs conformes. Nous commentons également le comportement des fonctions à trois points et fournissons un code numérique pour reproduire les résultats. La deuxième partie de la thèse étudie la chaîne quantique XXZ intégrable de spin-1/2 avec des conditions aux bords ouvertes, pour un nombre pair et impair de sites. Dans régime antiferromagnétique, nous utilisons l'Ansatz de Bethe Algébrique pour déterminer les configurations possibles en termes des champs aux bords. On retrouve les conditions d'existence d'états fondamentaux quasi dégénérés séparés par un gap au reste du spectre. Nous calculons l'aimantation au bord à température nulle et constatons qu'elle dépend du champ sur le bord opposé même dans la limite de chaîne semi-infinie. Nous calculons enfin la fonction d'autocorrélation temporelle au bord et montrons que dans le cas de taille paire, elle est finie à la limite de temps long à cause de la quasi-dégénérescence<br>This thesis is divided in two parts: The first one presents a 2D statistical model of correlated percolation on a toroidal lattice. We present a protocol to construct long-range correlated surfaces based on fractional Gaussian surfaces and then we relate the level sets to a family of correlated percolation models. The emerging clusters are then numerically studied, and we test their conformal symmetry by verifying that their planar-limit finite-size corrections follow the predictions of Conformal Field Theory. We comment also the behavior of three-point functions and provide a numerical code to reproduce the results.The second part of the thesis studies the quantum integrable XXZ spin-1/2 chain with open boundary conditions for even and odd number of sites. We concentrate in the anti-ferromagnetic regime and use the Algebraic Bethe Ansatz to determine the configurations that arise in terms of the boundary fields. We find the conditions of existence of quasi-degenerate ground states separated by a gap to the rest of the spectrum. We calculate the boundary magnetization at zero temperature and find that it depends on the field at the opposite edge even in the semi-infinite chain limit. We finally calculate the time autocorrelation function at the boundary and show that in the even-size case it is finite for the long-time limit as a result of the quasi-degeneracy
24
Baroud, Rawad. "Development and implementation of numerical models for the study of multilayered plates." Thesis, Paris Est, 2016. http://www.theses.fr/2016PESC1084/document.
Testo completoAbstract (sommario):
L’utilisation des multicouches prend de plus en plus d’ampleur dans le domaine des sciences de l’ingénieur, tout d’abord dans l’industrie, et plus récemment de plus en plus en Génie Civil. Qu’il s’agisse de complexes mêlant des polymères, du bois ou du béton, des efforts importants sont nécessaires pour la modélisation fine de ce type de matériaux. En effet, des phénomènes induits par l’anisotropie et l’hétérogénéité sont associés à ces multi-matériaux : effets de bords, dilatations thermiques différentielles, délaminages/décollements ou non linéarités de type viscosité, endommagement, plasticité dans les couches ou aux interfaces. Parmi les modèles proposés dans la littérature, on trouve par exemple des modèles monocouche équivalente ou de type "Layerwise" (une cinématique par couche). Appartenant à cette deuxième catégorie, des modèles ont été développés depuis quelques années dans le laboratoire Navier et permettent une description suffisamment fine pour aborder les problématiques spécifiques citées plus haut tout en conservant un caractère opératoire certain. En introduisant des efforts d’interfaces comme des efforts généralisés du modèle, ces approches ont montré leur efficacité vis-à-vis de la représentation des détails au niveau inter- et intra-couches. Il est alors aisé de proposer des comportements et des critères d’interfaces et d’être efficace pour la modélisation du délaminage ou décollement, phénomène très présent dans les composites multicouches assemblés et collés. Par conséquent, un programme éléments finis MPFEAP a été développé dans le laboratoire Navier. Le modèle a également été introduit sous la forme d’un User Element dans ABAQUS, dans sa forme la plus simple (interfaces parfaites).Un nouveau model layerwise est proposé dans ce mémoire pour les plaques multicouches, appelé "Statically Compatible Layerwise Stresses with first-order membrane stress approximations per layer in thickness direction" SCLS1. Le modèle est conforme aux équations d’équilibre 3D ainsi qu’aux conditions aux limites de bord libre. En outre, une version raffinée du nouveau modèle est obtenu en introduisant plusieurs couches mathématiques par couche physique. Le nouveau modèle a été mis en œuvre dans une nouvelle version du code éléments finis MPFEAP.En parallèle, un programme d’éléments finis basé sur la théorie Bending-Gradient développée dans le laboratoire Navier est proposé ici. Le modèle est une nouvelle théorie de plaque épaisse chargée hors-plan où les inconnues statiques sont celles de la théorie Love-Kirchhoff, à laquelle six composantes sont ajoutées représentant le gradient du moment de flexion. La théorie Bending- Gradient est obtenue à partir de la théorie Generalized-Reissner: cette dernière implique quinze degrés de liberté cinématiques, huit d’entre eux étant lié uniquement à la déformation de Poisson hors-plan, et donc l’idée principale de la théorie de plaque Bending-Gradient est de simplifier la théorie Generalized-Reissner en réglant ces huit d.o.f. à zéro et de négliger la contribution de la contrainte normale σ33 dans l’équation constitutive du modèle de plaque. Un programme éléments finis appelé BGFEAP a été développé pour la mise en œuvre de l’élément de Bending-Gradient. Un User Element dans Abaqus a été aussi développé pour la théorie Bending-Gradient<br>The use of multilayer is becoming increasingly important in the field of engineering, first in the industry, and more recently more and more in Civil Engineering. Whether complex blend of polymers, wood or concrete, significant efforts are required for accurate modeling of such materials. Indeed, phenomena induced anisotropy and heterogeneity are associated with these multi-material: edge effects, differential thermal expansion, delamination/detachment or nonlinearities viscosity type damage, plasticity in layers or interfaces. Among the models proposed in the literature, we found for example equivalent monolayer model or of "LayerWise" type (a kinematic per layer). Belonging to the second category, models have been developed in recent years in Navier allow a sufficiently detailed description to address specific issues mentioned above while maintaining a surgical nature. By introducing interface forces as generalized forces of the model, these approaches have demonstrated their effectiveness vis-à-vis the representation of details at inter- and intra-layers. It is then easy to offer behaviors and interfaces criteria and to be effective for modeling delamination or detachment, phenomenom very present in multilayered composites assembled and glued together. Therefore, a finite element program MPFEAP was developed in Navier laboratory. The model was also introduced as a User Element in ABAQUS, in its simplest form (perfect interfaces).A new layerwise model for multilayered plates is proposed in this dissertation, named Statically Compatible Layerwise Stresses with first-order membrane stress approximations per layer in thickness direction SCLS1. The model complies exactly with the 3D equilibrium equations and the free-edge boundary conditions. Also, a refined version of the new model is obtained by introducing several mathematical layers per physical layer. The new model has been implemented in a new version of the in-house finite element code MPFEAP.In parallel, a finite element program based on the Bending-Gradient theory which was developed in Navier laboratory, is proposed here. The model is a new plate theory for out-of-plane loaded thick plates where the static unknowns are those of the Love-Kirchhoff theory, to which six components are added representing the gradient of the bending moment. The Bending-Gradient theory is obtained from the Generalized-Reissner theory: the Generalized-Reissner theory involves fifteen kinematic degrees of freedom, eight of them being related only to out-of-plane Poisson’s distortion and thus, the main idea of the Bending-Gradient plate theory is to simplify the Generalized-Reissner theory by setting these eight d.o.f. to zero and to neglect the contribution of the normal stress σ33 in the plate model constitutive equation. A finite element program called BGFEAP has been developed for the implementation of the Bending-Gradient element. A User Element in Abaqus was also developed for the Bending-Gradient theory
25
Rastegar, Damoon. "Modification of Aeroelastic Model for Vertical Axes Wind Turbines." Thesis, Blekinge Tekniska Högskola, Sektionen för ingenjörsvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-3388.
Testo completoAbstract (sommario):
In wind turbines, flow pressure variations on the air-structure interface cause aerodynamic forces. Consequently the structure deforms and starts to move. The interaction between aerodynamic forces and structural deformations mainly concerns aeroelasticity. Since these two are coupled, they have to be considered simultaneously in cases which the deformations are not negligible in comparison to the other geometric dimensions. The purpose of this work is to improve the simulation model of a vertical axis wind turbine by modifying the structural model from undamped Euler-Bernoulli beam theory with lumped mass matrix to the more advanced Timoshenko beam theory with consistent mass matrix plus an additional damping term. The bending of the beam is then unified with longitudinal and torsional deformations based on a fixed shape cross-section assumption and the Saint-Venant torsion theory. The whole work has been carried out by implementing the finite element method using MATLAB code and implanting it in a previously developed package as a complement. Finally the results have been verified by qualitative comparisons with alternative simulations.
26
Mossberg, Eva. "Some numerical and analytical methods for equations of wave propagation and kinetic theory." Doctoral thesis, Karlstad : Fakulty of Technology and Science, Mathematics, Karlstads universitet, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-1848.
Testo completo
27
Kim, Kwangmoo. "Topics in the theory of inhomogeneous media composite superconductors and dielectrics /." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180537980.
Testo completo
28
Allexandre, Didier. "A Fast Numerical Method for Large-Scale Modeling of Cardiac Tissue and Linear Perturbation Theory for the Study and Control of Cardiac Spiral Wave Breakup." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1094046834.
Testo completo
29
Arruda, Alexandre Matos. "A infinitary system of the logic of least fixed-point." Universidade Federal do CearÃ, 2007. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=1325.
Testo completoAbstract (sommario):
FundaÃÃo Cearense de Apoio ao Desenvolvimento Cientifico e TecnolÃgico<br>A noÃÃo de menor ponto-fixo de um operador à amplamente aplicada na ciÃncia da computaÃÃo como, por exemplo, no contexto das linguagens de consulta para bancos de dados relacionais. Algumas extensÃes da LÃgica de Primeira-Ordem (FOL)1 com operadores de ponto-fixo em estruturas finitas, como a lÃgica de menor ponto-fixo (LFP)2, foram propostas para lidar com problemas relacionados à expressividade de FOL. A LFP captura as classes de complexidade PTIME sobre a classe das estruturas finitas ordenadas. A caracterizaÃÃo descritiva de classes computacionais à uma abordagem central em Teoria do Modelos Finitos (FMT)3. O teorema de Trakhtenbrot, considerado o ponto de partida para FMT, estabelece que a validade sobre modelos finitos nÃo à recursivamente enumerÃvel, isto Ã, a completude falha sobre modelos finitos. Este resultado à baseado na hipÃtese de que qualquer sistema dedutivo à de natureza finita. Entretanto, nos podemos relaxar tal hipÃtese como foi feito no escopo da teoria da prova para aritmÃtica. A teoria da prova tem raÃzes no programa de Hilbert. ConseqÃÃncias teÃricas da noÃÃo de prova sÃo, por exemplo, relacionadas a teoremas de normalizaÃÃo, consistÃncia, decidibilidade, e resultados de complexidade. A teoria da prova para aritmÃtica tambÃm à motivada pelos teoremas de incompletude de GÃdel, cujo alvo foi fornecer um exemplo de um princÃpio matemÃtico verdadeiro e significativo que nÃo à derivÃvel na aritmÃtica de primeira-ordem. Um meio de apresentar esta prova à baseado na definiÃÃo de um sistema de prova com uma regra infinitÃria, a w-rule, que estabiliza a consistÃncia da aritmÃtica de primeira-ordem atravÃs de uma perspectiva de teoria da prova. Motivados por esta prova, iremos propor aqui um sistema infinitÃrio de prova para LFP que nos permitirà investigar propriedades em teoria da prova. Com tal sistema dedutivo infinito, pretendemos apresentar uma teoria da prova para uma lÃgica tradicionalmente definida no escopo de FMT. Permanece aberto um caminho alternativo de provar resultados jà obtidos com FMT e tambÃm novos resultados do ponto de vista da teoria da prova. AlÃm disso, iremos propor um procedimento de normalizaÃÃo com restriÃÃes para este sistema dedutivo, que pode ser usado em um provador de teoremas para computar consultas em banco de dados relacionais<br>The notion of the least fixed-point of an operator is widely applied in computer science
as, for instance, in the context of query languages for relational databases. Some extensions
of FOL with _xed-point operators on finite structures, as the least fixed-point logic
(LFP), were proposed to deal with problem problems related to the expressivity of FOL.
LFP captures the complexity class PTIME over the class of _nite ordered structures. The
descriptive characterization of computational classes is a central issue within _nite model
theory (FMT). Trakhtenbrot's theorem, considered the starting point of FMT, states that
validity over finite models is not recursively enumerable, that is, completeness fails over
finite models. This result is based on an underlying assumption that any deductive system
is of finite nature. However, we can relax such assumption as done in the scope of
proof theory for arithmetic. Proof theory has roots in the Hilbert's programme. Proof
theoretical consequences are, for instance, related to normalization theorems, consistency,
decidability, and complexity results. The proof theory for arithmetic is also motivated
by Godel incompleteness theorems. It aims to o_er an example of a true mathematically
meaningful principle not derivable in first-order arithmetic. One way of presenting this
proof is based on a definition of a proof system with an infinitary rule, the w-rule, that establishes
the consistency of first-order arithmetic through a proof-theoretical perspective.
Motivated by this proof, here we will propose an in_nitary proof system for LFP that
will allow us to investigate proof theoretical properties. With such in_nitary deductive
system, we aim to present a proof theory for a logic traditionally defined within the scope
of FMT. It opens up an alternative way of proving results already obtained within FMT
and also new results through a proof theoretical perspective. Moreover, we will propose a
normalization procedure with some restrictions on the rules, such this deductive system
can be used in a theorem prover to compute queries on relational databases.
30
Arruda, Alexandre Matos. "Um sistema infinitário para a lógica de menor ponto fixo." reponame:Repositório Institucional da UFC, 2007. http://www.repositorio.ufc.br/handle/riufc/16927.
Testo completoAbstract (sommario):
ARRUDA, Alexandre Matos. Um sistema infinitário para a lógica de menor ponto fixo. 2007. 91 f. : Dissertação (mestrado) - Universidade Federal do Ceará, Departamento de Computação, Fortaleza-CE, 2007.<br>Submitted by guaracy araujo (guaraa3355@gmail.com) on 2016-05-20T15:28:27Z
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Previous issue date: 2007<br>The notion of the least fixed-point of an operator is widely applied in computer science as, for instance, in the context of query languages for relational databases. Some extensions of FOL with _xed-point operators on finite structures, as the least fixed-point logic (LFP), were proposed to deal with problem problems related to the expressivity of FOL. LFP captures the complexity class PTIME over the class of _nite ordered structures. The descriptive characterization of computational classes is a central issue within _nite model theory (FMT). Trakhtenbrot's theorem, considered the starting point of FMT, states that validity over finite models is not recursively enumerable, that is, completeness fails over finite models. This result is based on an underlying assumption that any deductive system is of finite nature. However, we can relax such assumption as done in the scope of proof theory for arithmetic. Proof theory has roots in the Hilbert's programme. Proof theoretical consequences are, for instance, related to normalization theorems, consistency, decidability, and complexity results. The proof theory for arithmetic is also motivated by Godel incompleteness theorems. It aims to o_er an example of a true mathematically meaningful principle not derivable in first-order arithmetic. One way of presenting this proof is based on a definition of a proof system with an infinitary rule, the w-rule, that establishes the consistency of first-order arithmetic through a proof-theoretical perspective. Motivated by this proof, here we will propose an in_nitary proof system for LFP that will allow us to investigate proof theoretical properties. With such in_nitary deductive system, we aim to present a proof theory for a logic traditionally defined within the scope of FMT. It opens up an alternative way of proving results already obtained within FMT and also new results through a proof theoretical perspective. Moreover, we will propose a normalization procedure with some restrictions on the rules, such this deductive system can be used in a theorem prover to compute queries on relational databases.<br>A noção de menor ponto-fixo de um operador é amplamente aplicada na ciência da computação como, por exemplo, no contexto das linguagens de consulta para bancos de dados relacionais. Algumas extensões da Lógica de Primeira-Ordem (FOL)1 com operadores de ponto-fixo em estruturas finitas, como a lógica de menor ponto-fixo (LFP)2, foram propostas para lidar com problemas relacionados á expressividade de FOL. A LFP captura as classes de complexidade PTIME sobre a classe das estruturas finitas ordenadas. A caracterização descritiva de classes computacionais é uma abordagem central em Teoria do Modelos Finitos (FMT)3. O teorema de Trakhtenbrot, considerado o ponto de partida para FMT, estabelece que a validade sobre modelos finitos não é recursivamente enumerável, isto é, a completude falha sobre modelos finitos. Este resultado é baseado na hipótese de que qualquer sistema dedutivo é de natureza finita. Entretanto, nos podemos relaxar tal hipótese como foi feito no escopo da teoria da prova para aritmética. A teoria da prova tem raízes no programa de Hilbert. Conseqüências teóricas da noção de prova são, por exemplo, relacionadas a teoremas de normalização, consistência, decidibilidade, e resultados de complexidade. A teoria da prova para aritmética também é motivada pelos teoremas de incompletude de Gödel, cujo alvo foi fornecer um exemplo de um princípio matemático verdadeiro e significativo que não é derivável na aritmética de primeira-ordem. Um meio de apresentar esta prova é baseado na definição de um sistema de prova com uma regra infinitária, a w-rule, que estabiliza a consistência da aritmética de primeira-ordem através de uma perspectiva de teoria da prova. Motivados por esta prova, iremos propor aqui um sistema infinitário de prova para LFP que nos permitirá investigar propriedades em teoria da prova. Com tal sistema dedutivo infinito, pretendemos apresentar uma teoria da prova para uma lógica tradicionalmente definida no escopo de FMT. Permanece aberto um caminho alternativo de provar resultados já obtidos com FMT e também novos resultados do ponto de vista da teoria da prova. Além disso, iremos propor um procedimento de normalização com restrições para este sistema dedutivo, que pode ser usado em um provador de teoremas para computar consultas em banco de dados relacionais
31
Bejjani, Nadine. "Wave propagation in multilayered plates : the Bending-Gradient model and the asymptotic expansion method." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC1025.
Testo completoAbstract (sommario):
Cette thèse est consacrée à la modélisation de la propagation des ondes planes dans les plaques multicouches infinies, dans le cadre de l'élasticité linéaire. L’objet du travail est de trouver une approximation analytique ou semi-analytique des relations de dispersion des ondes lorsque le rapport de l'épaisseur de la plaque sur la longueur d'onde est petit. Ces relations de dispersion, liant la fréquence angulaire et le nombre d'onde, fournissent des informations clés sur les caractéristiques de propagation des différents modes. On propose dans cette thèse deux modélisations : le modèle du Bending-Gradient et la méthode des développements asymptotiques. La pertinence de ces méthodes est testée en comparant leurs prédictions à celles des théories de plaques bien connues, et à des résultats de référence obtenus par la méthode des éléments finis. Au préalable, dans la première partie de la thèse, une justification mathématique de la théorie du Bending-Gradient dans le cadre statique est réalisée à l’aide des méthodes variationnelles. Il s'agit d'abord d'identifier les espaces mathématiques dans lesquels les problèmes variationnels du Bending-Gradient sont bien posés. Puis, des théorèmes d'existence et d'unicité des solutions correspondantes sont ensuite formulés et prouvés. La deuxième partie est consacrée à la formulation des équations du mouvement du Bending-Gradient. Des simulations numériques sont effectuées pour plusieurs types d'empilements, permettant ainsi de tester la validité du modèle pour la modélisation de la propagation des ondes de flexion. La troisième partie est dédiée à l'analyse asymptotique des équations tridimensionnelles du mouvement, menée à bien grâce à la méthode des développements asymptotiques, le petit paramètre étant le rapport de l'épaisseur sur la longueur d'onde. En supposant que les champs tridimensionnels s'écrivent comme des séries en puissance du petit paramètre, on obtient une succession de problèmes à résoudre en cascade. La validité de cette méthode est évaluée par comparaison avec la méthode des éléments finis<br>This thesis is dedicated to the modelling of plane wave propagation in infinite multilayered plates, in the context of linear elasticity. The aim of this work is to find an analytical or semi-analytical approximation of the wave dispersion relations when the ratio of the thickness to the wavelength is small. The dispersion relations, linking the angular frequency and the wave number, provide key information about the propagation characteristics of the wave modes. Two methods are proposed in this thesis: the Bending-Gradient model and the asymptotic expansion method. The relevance of these methods is tested by comparing their predictions to those of well-known plate theories, and to reference results computed using the finite element method. Preliminarily, the first part of the thesis is devoted to the mathematical justification of the Bending-Gradient theory in the static framework using variational methods. The first step is to identify the mathematical spaces in which the variational problems of the Bending-Gradient are well posed. A series of existence and uniqueness theorems of the corresponding solutions are then formulated and proved. The second part is dedicated to the formulation of the equations of motion of the Bending-Gradient theory. Numerical simulations are realized for different types of layer stacks to assess the ability of this model to correctly predict the propagation of flexural waves. The third part is concerned with the asymptotic analysis of the three-dimensional equations of motion, carried out using the asymptotic expansion method, the small parameter being the ratio of the thickness to the wavelength. Assuming that the three-dimensional fields can be written as expansions in power of the small parameter, a series of problems which can be solved recursively is obtained. The validity of this method is evaluated by comparison with the finite element method
32
Dona, Marco. "Static and dynamic analysis of multi-cracked beams with local and non-local elasticity." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/14893.
Testo completoAbstract (sommario):
The thesis presents a novel computational method for analysing the static and dynamic behaviour of a multi-damaged beam using local and non-local elasticity theories. Most of the lumped damage beam models proposed to date are based on slender beam theory in classical (local) elasticity and are limited by inaccuracies caused by the implicit assumption of the Euler-Bernoulli beam model and by the spring model itself, which simplifies the real beam behaviour around the crack. In addition, size effects and material heterogeneity cannot be taken into account using the classical elasticity theory due to the absence of any microstructural parameter. The proposed work is based on the inhomogeneous Euler-Bernoulli beam theory in which a Dirac's delta function is added to the bending flexibility at the position of each crack: that is, the severer the damage, the larger is the resulting impulsive term. The crack is assumed to be always open, resulting in a linear system (i.e. nonlinear phenomena associated with breathing cracks are not considered). In order to provide an accurate representation of the structure's behaviour, a new multi-cracked beam element including shear effects and rotatory inertia is developed using the flexibility approach for the concentrated damage. The resulting stiffness matrix and load vector terms are evaluated by the unit-displacement method, employing the closed-form solutions for the multi-cracked beam problem. The same deformed shapes are used to derive the consistent mass matrix, also including the rotatory inertia terms. The two-node multi-damaged beam model has been validated through comparison of the results of static and dynamic analyses for two numerical examples against those provided by a commercial finite element code. The proposed model is shown to improve the computational efficiency as well as the accuracy, thanks to the inclusion of both shear deformations and rotatory inertia. The inaccuracy of the spring model, where for example for a rotational spring a finite jump appears on the rotations' profile, has been tackled by the enrichment of the elastic constitutive law with higher order stress and strain gradients. In particular, a new phenomenological approach based upon a convenient form of non-local elasticity beam theory has been presented. This hybrid non-local beam model is able to take into account the distortion on the stress/strain field around the crack as well as to include the microstructure of the material, without introducing any additional crack related parameters. The Laplace's transform method applied to the differential equation of the problem allowed deriving the static closed-form solution for the multi-cracked Euler-Bernoulli beams with hybrid non-local elasticity. The dynamic analysis has been performed using a new computational meshless method, where the equation of motions are discretised by a Galerkin-type approximation, with convenient shape functions able to ensure the same grade of approximation as the beam element for the classical elasticity. The importance of the inclusion of microstructural parameters is addressed and their effects are quantified also in comparison with those obtained using the classical elasticity theory.
33
Neves, J?lia Barbosa. "Aplica??o do m?todo das diferen?as finitas energ?ticas na modelagem do concreto refor?ado com fibras curtas de a?o sob flex?o." Universidade Estadual de Feira de Santana, 2013. http://localhost:8080/tede/handle/tede/167.
Testo completoAbstract (sommario):
Submitted by Verena Bastos (verena@uefs.br) on 2015-08-05T21:29:18Z
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Previous issue date: 2013-09-24<br>Funda??o de Amparo ? Pesquisa do Estado de S?o Paulo - FAPESP<br>The prediction of the reinforced concrete beams behavior under bending is essential
to design these elements. Usually the models do not incorporate the concrete stress
contribution, which may underestimate the structural element strain that use steel fiber
reinforced concrete (SFRC) under permanent or temporary loads. This work presents a
variational formulation based on the finite difference energy method (EFDM) in
predicting the flexural behavior of concrete beams reinforced, that uses SFRC. The
proposed model uses the classical lamination theory (CLT) with a damage model
(Mazars, 1984) applied to the SFRC. The reinforcement was considered as a layer of a
perfect elastic-plastic material. Comparing the load-displacement numerical results with
those of the literature to reinforced concrete beams demonstrates the consistency of the
proposed model.<br>A previs?o do comportamento de vigas de concreto armado sob flex?o ? fundamental para o adequado dimensionamento destes elementos. Usualmente, os modelos n?o incorporam a contribui??o do concreto tracionado, o que pode subestimar as deforma??es no elemento estrutural que utilizem o concreto refor?ado com fibras (CRFA) sob cargas de curta e longa dura??o. No presente trabalho ? apresentada uma formula??o variacional com base no m?todo das diferen?as finitas energ?ticas (MDFE) para a previs?o do comportamento ? flex?o de vigas de concreto simples ou armado refor?adas com fibras de a?o. O modelo proposto combina a teoria cl?ssica de laminados (TCL) com um modelo de dano (Mazars, 1984) aplicado ao concreto. O refor?o (armadura longitudinal) foi considerado como uma l?mina de um material
elasto-pl?stico perfeito. A compara??o dos resultados num?ricos com resultados encontrados na literatura para vigas de concreto armado, em termos de cargadeslocamento, demonstra a coer?ncia do modelo proposto.
34
Neman, Azadeh. "Propriétés combinatoires et modèle-théoriques des groupes." Phd thesis, Université Claude Bernard - Lyon I, 2009. http://tel.archives-ouvertes.fr/tel-00679429.
Testo completoAbstract (sommario):
Notre travail ici concerne certaines pistes pour des constructions nouveaux groupes, et en particulier de contre-exemples à la conjecture de Cherlin-Zilber. On parvient à trouver une réponse pour la stabilité de groupes CSA existentiellement clos. On exhibe un mot de groupe en deux variables qui a la propriété d'indépendance par rapport à la classe de groupes hyperboliques sans torsion. On en déduit que l'équation correspondante donne la propriété d'indépendance des groupes CSA existentiellement clos, ce qui en particulier implique leur instabilité. En outre, on prouve que les équations, et en particulier les ensembles définissables sans quantificateurs, définissent des ensembles stables dans les boules bornées des produits libres de groupes, en utilisant la version finie du théorème de Ramsey. Enfin, on introduit certains groupes construits comme tours particulières de produits libres et d'extensions HNN.
35
Gabriel, Naveen. "Automatic Speech Recognition in Somali." Thesis, Linköpings universitet, Statistik och maskininlärning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-166216.
Testo completoAbstract (sommario):
The field of speech recognition during the last decade has left the research stage and found its way into the public market, and today, speech recognition software is ubiquitous around us. An automatic speech recognizer understands human speech and represents it as text. Most of the current speech recognition software employs variants of deep neural networks. Before the deep learning era, the hybrid of hidden Markov model and Gaussian mixture model (HMM-GMM) was a popular statistical model to solve speech recognition. In this thesis, automatic speech recognition using HMM-GMM was trained on Somali data which consisted of voice recording and its transcription. HMM-GMM is a hybrid system in which the framework is composed of an acoustic model and a language model. The acoustic model represents the time-variant aspect of the speech signal, and the language model determines how probable is the observed sequence of words. This thesis begins with background about speech recognition. Literature survey covers some of the work that has been done in this field. This thesis evaluates how different language models and discounting methods affect the performance of speech recognition systems. Also, log scores were calculated for the top 5 predicted sentences and confidence measures of pre-dicted sentences. The model was trained on 4.5 hrs of voiced data and its corresponding transcription. It was evaluated on 3 mins of testing data. The performance of the trained model on the test set was good, given that the data was devoid of any background noise and lack of variability. The performance of the model is measured using word error rate(WER) and sentence error rate (SER). The performance of the implemented model is also compared with the results of other research work. This thesis also discusses why log and confidence score of the sentence might not be a good way to measure the performance of the resulting model. It also discusses the shortcoming of the HMM-GMM model, how the existing model can be improved, and different alternatives to solve the problem.
36
Steinle, Peter John. "Finite difference methods for the advection equation /." Title page, table of contents and abstract only, 1993. http://web4.library.adelaide.edu.au/theses/09PH/09phs8224.pdf.
Testo completo
37
Stewart, Michael. "Asymptotic methods for tests of homogeneity for finite mixture models." Connect to full text, 2002. http://hdl.handle.net/2123/855.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Sydney, 2002.<br>Title from title screen (viewed Apr. 28, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Mathematics and Statistics, Faculty of Science. Includes bibliography. Also available in print form.
38
Jayaram, Vikram. "Reduced dimensionality hyperspectral classification using finite mixture models." To access this resource online via ProQuest Dissertations and Theses @ UTEP, 2009. http://0-proquest.umi.com.lib.utep.edu/login?COPT=REJTPTU0YmImSU5UPTAmVkVSPTI=&clientId=2515.
Testo completo
39
Shabani, Behnam. "Wave-Associated Seabed Behaviour near Submarine Buried Pipelines." University of Sydney, 2008. http://hdl.handle.net/2123/3532.
Testo completoAbstract (sommario):
Master of Engineering (Research)<br>Soil surrounding a submarine buried pipeline consolidates as ocean waves propagate over the seabed surface. Conventional models for the analysis of soil behaviour near the pipeline assume a two-dimensional interaction problem between waves, the seabed soil, and the structure. In other words, it is often considered that water waves travel normal to the orientation of pipeline. However, the real ocean environment is three-dimensional and waves approach the structure from various directions. It is therefore the key objective of the present research to study the seabed behaviour in the vicinity of marine pipelines from a three-dimensional point of view. A three-dimensional numerical model is developed based on the Finite Element Method to analyse the so-called momentary behaviour of soil under the wave loading. In this model, the pipeline is assumed to be rigid and anchored within a rigid impervious trench. A non-slip condition is considered to exist between the pipe and the surrounding soil. Quasi-static soil consolidation equations are then solved with the aid of the proposed FE model. In this analysis, the seabed behaviour is assumed to be linear elastic with the soil strains remaining small. The influence of wave obliquity on seabed responses, i.e. the pore pressure and soil stresses, are then studied. It is revealed that three-dimensional characteristics systematically affect the distribution of soil response around the circumference of the underwater pipeline. Numerical results suggest that the effect of wave obliquity on soil responses can be explained through the following two mechanisms: (i) geometry-based three-dimensional influences, and (ii) the formation of inversion nodes. Further, a parametric study is carried out to investigate the influence of soil, wave and pipeline properties on wave-associated pore pressure as well as principal effective and shear stresses within the porous bed, with the aid of proposed three-dimensional model. There is strong evidence in the literature that the failure of marine pipelines often stems from the instability of seabed soil close to this structure, rather than from construction deficiencies. The wave-induced seabed instability is either associated with the soil shear failure or the seabed liquefaction. Therefore, the developed three-dimensional FE model is used in this thesis to further investigate the instability of seabed soil in the presence of a pipeline. The widely-accepted criterion, which links the soil liquefaction to the wave-induced excess pressure is used herein to justify the seabed liquefaction. It should be pointed out that although the present analysis is only concerned with the momentary liquefaction of seabed soil, this study forms the basis for the three-dimensional analysis of liquefaction due to the residual mechanisms. The latter can be an important subject for future investigations. At the same time, a new concept is developed in this thesis to apply the dynamic component of soil stress angle to address the phenomenon of wave-associated soil shear failure. At this point, the influence of three-dimensionality on the potentials for seabed liquefaction and shear failure around the pipeline is investigated. Numerical simulations reveal that the wave obliquity may not notably affect the risk of liquefaction near the underwater pipeline. But, it significantly influences the potential for soil shear failure. Finally, the thesis proceeds to a parametric study on effects of wave, soil and pipeline characteristics on excess pore pressure and stress angle in the vicinity of the structure.
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Mahlasela, Zuko. "Finite fuzzy sets, keychains and their applications." Thesis, Rhodes University, 2009. http://hdl.handle.net/10962/d1005220.
Testo completoAbstract (sommario):
The idea of keychains, an (n+1)-tuple of non-increasing real numbers in the unit interval always including 1, naturally arises in study of finite fuzzy set theory. They are a useful concept in modeling ideas of uncertainty especially those that arise in Economics, Social Sciences, Statistics and other subjects. In this thesis we define and study some basic properties of keychains with reference to Partially Ordered Sets, Lattices, Chains and Finite Fuzzy Sets. We then examine the role of keychains and their lattice diagrams in representing uncertainties that arise in such problems as in preferential voting patterns, outcomes of competitions and in Economics - Preference Relations.
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Hoyos, Gomez Nancy Milena. "Finite sample properties of the maximum likelihood estimator in continuous time models." Thesis, University of Essex, 2017. http://repository.essex.ac.uk/18736/.
Testo completoAbstract (sommario):
This dissertation consists of three papers on finite sample properties of the maximum likelihood (ML) estimator of parameters in continuous time dynamic models. In the first chapter, we obtain analytical expressions to approximate the bias and variance of the ML estimator in a univariate model with a known mean. We analyze two cases, when the variable of interest is a stock and when it is a flow. We also study the effect of the initial condition by considering both a fixed and a random initial value. A Monte Carlo study suggests that the performance of the formulae is reasonably good. Analytical bias expressions are then used in the second chapter to compute bias corrected estimators. This chapter also explores other methods for bias reduction that have been employed in the literature, these being the bootstrap, jackknife, and indirect inference. A Monte Carlo experiment shows that all approaches deliver substantial bias reductions. We also explore the robustness of the results to model misspecifications, and provide an empirical application to the broad effective exchange rate series for euro area. The third chapter derives the exact discrete representation corresponding to a cointegrated system of mixed first- and second-order stochastic differential equations with mixed sampling and observable stochastic trends. We also provide some formulae to implement the Gaussian estimation and conduct a Monte Carlo experiment to examine the finite sample properties of the Gaussian estimator. Monte Carlo simulations suggest that the bias and variance of the estimators of the short-run, long-run and adjustment coefficients as well as the variance of the intercepts are mainly determined by the data span, while the bias and variance of the covariance coefficients seem to depend on the sample size.
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Hinkelmann, Franziska Babette. "Algebraic theory for discrete models in systems biology." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/28509.
Testo completoAbstract (sommario):
This dissertation develops algebraic theory for discrete models in systems biology. Many discrete model types can be translated into the framework of polynomial dynamical systems (PDS), that is, time- and state-discrete dynamical systems over a finite field where the transition function for each variable is given as a polynomial. This allows for using a range of theoretical and computational tools from computer algebra, which results in a powerful computational engine for model construction, parameter estimation, and analysis methods. Formal definitions and theorems for PDS and the concept of PDS as models of biological systems are introduced in section 1.3.
Constructing a model for given time-course data is a challenging problem. Several methods for reverse-engineering, the process of inferring a model solely based on experimental data, are described briefly in section 1.3. If the underlying dependencies of the model components are known in addition to experimental data, inferring a "good" model amounts to parameter estimation.
Chapter 2 describes a parameter estimation algorithm that infers a special class of polynomials, so called nested canalyzing functions. Models consisting of nested canalyzing functions have been shown to exhibit desirable biological properties, namely robustness and stability. The algorithm is based on the parametrization of nested canalyzing functions. To demonstrate the feasibility of the method, it is applied to the cell-cycle network of budding yeast.
Several discrete model types, such as Boolean networks, logical models, and bounded Petri nets, can be translated into the framework of PDS. Section 3 describes how to translate agent-based models into polynomial dynamical systems.
Chapter 4, 5, and 6 are concerned with analysis of complex models. Section 4 proposes a new method to identify steady states and limit cycles. The method relies on the fact that attractors correspond to the solutions of a system of polynomials over a finite field, a long-studied problem in algebraic geometry which can be efficiently solved by computing Gröbner bases. Section 5 introduces a bit-wise implementation of a Gröbner basis algorithm for Boolean polynomials. This implementation has been incorporated into the core engine of Macaulay2. Chapter 6 discusses bistability for Boolean models formulated as polynomial dynamical systems.<br>Ph. D.
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Lázaro, Fernández Carlos Manuel. "Formulación material y espacial del modelo geometricamente exacto de piezas alargadas." Doctoral thesis, Universitat Politècnica de València, 2008. http://hdl.handle.net/10251/1872.
Testo completoAbstract (sommario):
El análisis de la respuesta mecánica de piezas alargadas que experimentan grandes desplazamientos y rotaciones constituye un campo en el que se han producido avances significativos en las tres últimas décadas, tanto desde el punto de vista de la formulación de modelos físicos como de la búsqueda de soluciones numéricas. El ámbito de aplicación de este tipo de modelos se separa quizás del abanico de problemas de los que tradicionalmente se ha ocupado la ingeniería civil, aproximándose más a situaciones propias de otras disciplinas, como la aeronáutica, la robótica o la biomecánica.
Dentro de la variedad de modelos en una dimensión desarrollados para el análisis no lineal de piezas alargadas, el propuesto por Simó como extensión del trabajo de Reissner es capaz de reproducir rotaciones arbitrariamente grandes de las secciones transversales. Su sencillez conceptual y la potencia de las soluciones numéricas basadas en él lo hanconvertido en referencia obligada y punto de partida de muchas investigaciones recientes. El propio Simó introdujo la denominación de \emph{modelo geométricamente exacto de piezas alargadas} para referirse a él. No obstante, el modelo de Reissner--Simó no está libre de dificultades. Éstas derivan principalmente del tratamiento exacto de las rotaciones, que exige trabajar en un espacio de configuraciones no lineal ni conmutativo.
Esta tesis examina los fundamentos del modelo geométricamente exacto y su conexión con la teoría no lineal de la elasticidad. La relación entre variables materiales y espaciales a través de la transformación definida por la rotación de cada sección establece el método de análisis. En un primer paso se ha desarrollado completamente la cinemática del modelo y las ecuaciones de campo en sus dos facetas --material y espacial--, lo que ha permitido sistematizar el proceso deductivo y aportar algunos resultados teóricos novedosos. El análisis del problema desde el punto de vista variacional ha puesto de manifiesto las conexiones<br>Lázaro Fernández, CM. (2005). Formulación material y espacial del modelo geometricamente exacto de piezas alargadas [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/1872<br>Palancia
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Baker, Peter John. "Applied Bayesian modelling in genetics." Thesis, Queensland University of Technology, 2001.
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Bevan, Graeme Rhys. "A practical investigation into the measurement of forces on the stator teeth of electrical machines." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1079.
Testo completoAbstract (sommario):
Submitted to the Department of Electrical Engineering in Fulfilment of the
Requirements for the Magister Technologiae in Electrical Engineering at the
CAPE PENINSULA UNIVERSITY OF TECHNOLOGY
SUPERVISOR: E. VOSS
NOVEMBER 2013<br>Radial and peripheral displacement of stator teeth in electrical machines is known to be
the cause of undesired vibration which leads to noise. This thesis serves to investigate the
possibility of physically measuring the radial displacement of stator teeth caused by
electromagnetic forces which, to the author’s knowledge, has not yet been achieved. A
simplified practical approach is adopted in order to address the inherent difficulties
attached to this problem, and the measurement of displacement is done by means of an
experimental rig where a tooth is subjected to magnetic force acting over an air gap.
Three experiments are carried out, each comprising ten tests, the results of which are
compared in order to gain some idea as to the magnitudes of displacement which can be
expected over a range of applied air gap flux densities. The aim of this work is to observe
the displacement response of magnetised EM core material when acted upon by forces,
and to see if the measured results agree with the elastic displacement predicted by a wellknown
formula. It will be shown that although the measured results are in the same range
as the predicted results, there is a deviation from the predicted linearity due to certain
characteristics of the force rig, which are explained.
The chosen measurement method is capacitive displacement and is shown to be a viable
alternative to the more commonly used search coils and vibrometers in past literatures,
especially when measuring displacements on the nano-scale. In addition, this study shows
the importance of using 3D finite element software to simulate the electromagnetic model
when saturation is present in the core of the test specimen. The important findings of this
work are discussed in detail, and some ideas put forward, in an attempt to establish a
starting point for future related work in the measurement of electromagnetic forceinduced
displacement of stator teeth in electrical machines.
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Hart, Derrick N. "Finite Field Models of Roth's Theorem in One and Two Dimensions." Thesis, Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/11516.
Testo completoAbstract (sommario):
Recent work on many problems in additive combinatorics, such as Roth's Theorem, has shown the usefulness of first studying the problem in a finite field environment. Using the techniques of Bourgain to give a result in other settings such as general abelian groups, the author gives a walk through, including proof, of Roth's theorem in both the one dimensional and two dimensional cases (it would be more accurate to refer to the two dimensional case as Shkredov's Theorem). In the one dimensional case the argument is at its base Meshulam's but the structure will be essentially Green's. Let Ϝⁿ [subscript p], p ≠ 2 be the finite field of cardinality N = pⁿ. For large N, any subset A ⊂ Ϝⁿ [subscript p] of cardinality ∣A ∣≳ N ∕ log N must contain a triple of the form {x, x + d, x + 2d} for x, d ∈ Ϝⁿ [subscript p], d ≠ 0. In the two dimensional case the argument is Lacey and McClain who made considerable refinements to this argument of Green who was bringing the argument to the finite field case from a paper of Shkredov. Let Ϝ ⁿ ₂ be the finite field of cardinality N = 2ⁿ. For all large N, any subset A⊂ Ϝⁿ ₂ × Ϝⁿ ₂ of cardinality ∣A ∣≳ N ² (log n) − [superscript epsilon], ε <, 1, must contain a corner {(x, y), (x + d, y), (x, y + d)} for x, y, d ∈ Ϝⁿ₂ and d ≠ 0.
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Laubner, Bastian. "The structure of graphs and new logics for the characterization of Polynomial Time." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät II, 2011. http://dx.doi.org/10.18452/16335.
Testo completoAbstract (sommario):
Diese Arbeit leistet Beiträge zu drei Gebieten der deskriptiven Komplexitätstheorie. Zunächst adaptieren wir einen repräsentationsinvarianten Graphkanonisierungsalgorithmus mit einfach exponentieller Laufzeit von Corneil und Goldberg (1984) und folgern, dass die Logik "Choiceless Polynomial Time with Counting" auf Strukturen, deren Relationen höchstens Stelligkeit 2 haben, gerade die Polynomialzeit-Eigenschaften (PTIME) von Fragmenten logarithmischer Größe charakterisiert. Der zweite Beitrag untersucht die deskriptive Komplexität von PTIME-Berechnungen auf eingeschränkten Graphklassen. Wir stellen eine neuartige Normalform von Intervallgraphen vor, die sich in Fixpunktlogik mit Zählen (FP+C) definieren lässt, was bedeutet, dass FP+C auf dieser Graphklasse PTIME charakterisiert. Wir adaptieren außerdem unsere Methoden, um einen kanonischen Beschriftungsalgorithmus für Intervallgraphen zu erhalten, der sich mit logarithmischer Platzbeschränkung (LOGSPACE) berechnen lässt. Im dritten Teil der Arbeit beschäftigt uns die ungelöste Frage, ob es eine Logik gibt, die alle Polynomialzeit-Berechnungen charakterisiert. Wir führen eine Reihe von Ranglogiken ein, die die Fähigkeit besitzen, den Rang von Matrizen über Primkörpern zu berechnen. Wir zeigen, dass diese Ergänzung um lineare Algebra robuste Logiken hervor bringt, deren Ausdrucksstärke die von FP+C übertrifft. Außerdem beweisen wir, dass Ranglogiken strikt an Ausdrucksstärke gewinnen, wenn wir die Zahl an Variablen erhöhen, die die betrachteten Matrizen indizieren. Dann bauen wir eine Brücke zur klassischen Komplexitätstheorie, indem wir über geordneten Strukturen eine Reihe von Komplexitätsklassen zwischen LOGSPACE und PTIME durch Ranglogiken charakterisieren. Die Arbeit etabliert die stärkste der Ranglogiken als Kandidat für die Charakterisierung von PTIME und legt nahe, dass Ranglogiken genauer erforscht werden müssen, um weitere Fortschritte im Hinblick auf eine Logik für Polynomialzeit zu erzielen.<br>This thesis is making contributions to three strands of descriptive complexity theory. First, we adapt a representation-invariant, singly exponential-time graph canonization algorithm of Corneil and Goldberg (1984) and conclude that on structures whose relations are of arity at most 2, the logic "Choiceless Polynomial Time with Counting" precisely characterizes the polynomial-time (PTIME) properties of logarithmic-size fragments. The second contribution investigates the descriptive complexity of PTIME computations on restricted classes of graphs. We present a novel canonical form for the class of interval graphs which is definable in fixed-point logic with counting (FP+C), which shows that FP+C captures PTIME on this graph class. We also adapt our methods to obtain a canonical labeling algorithm for interval graphs which is computable in logarithmic space (LOGSPACE). The final part of this thesis takes aim at the open question whether there exists a logic which generally captures polynomial-time computations. We introduce a variety of rank logics with the ability to compute the ranks of matrices over (finite) prime fields. We argue that this introduction of linear algebra results in robust logics whose expressiveness surpasses that of FP+C. Additionally, we establish that rank logics strictly gain in expressiveness when increasing the number of variables that index the matrices we consider. Then we establish a direct connection to standard complexity theory by showing that in the presence of orders, a variety of complexity classes between LOGSPACE and PTIME can be characterized by suitable rank logics. Our exposition provides evidence that rank logics are a natural object to study and establishes the most expressive of our rank logics as a viable candidate for capturing PTIME, suggesting that rank logics need to be better understood if progress is to be made towards a logic for polynomial time.
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Bischoff, Manfred. "Theorie und Numerik einer dreidimensionalen Schalenformulierung." [S.l.] : Universität Stuttgart , Fakultät Bauingenieur- und Vermessungswesen, 1999. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB8536741.
Testo completo
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Pontaza, Juan Pablo. "Least-squares variational principles and the finite element method: theory, formulations, and models for solid and fluid mechanics." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/288.
Testo completoAbstract (sommario):
We consider the application of least-squares variational principles and the finite element method to the numerical solution of boundary value problems arising in the fields of solidand fluidmechanics.For manyof these problems least-squares principles offer many theoretical and computational advantages in the implementation of the corresponding finite element model that are not present in the traditional weak form Galerkin finite element model.Most notably, the use of least-squares principles leads to a variational unconstrained minimization problem where stability conditions such as inf-sup conditions (typically arising in mixed methods using weak form Galerkin finite element formulations) never arise. In addition, the least-squares based finite elementmodelalways yields a discrete system ofequations witha symmetric positive definite coeffcientmatrix.These attributes, amongst manyothers highlightedand detailed in this work, allow the developmentofrobust andeffcient finite elementmodels for problems of practical importance. The research documented herein encompasses least-squares based formulations for incompressible and compressible viscous fluid flow, the bending of thin and thick plates, and for the analysis of shear-deformable shell structures.
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Andersson, Per-Åke. "Computation of Thermal Development in Injection Mould Filling, based on the Distance Model." Licentiate thesis, Linköping University, Linköping University, Optimization, 2002. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-5733.
Testo completoAbstract (sommario):
<p>The heat transfer in the filling phase of injection moulding is studied, based on Gunnar Aronsson’s distance model for flow expansion ([Aronsson], 1996).</p><p>The choice of a thermoplastic materials model is motivated by general physical properties, admitting temperature and pressure dependence. Two-phase, per-phase-incompressible, power-law fluids are considered. The shear rate expression takes into account pseudo-radial flow from a point inlet.</p><p>Instead of using a finite element (FEM) solver for the momentum equations a general analytical viscosity expression is used, adjusted to current axial temperature profiles and yielding expressions for axial velocity profile, pressure distribution, frozen layer expansion and special front convection.</p><p>The nonlinear energy partial differential equation is transformed into its conservative form, expressed by the internal energy, and is solved differently in the regions of streaming and stagnant flow, respectively. A finite difference (FD) scheme is chosen using control volume discretization to keep truncation errors small in the presence of non-uniform axial node spacing. Time and pseudo-radial marching is used. A local system of nonlinear FD equations is solved. In an outer iterative procedure the position of the boundary between the “solid” and “liquid” fluid cavity parts is determined. The uniqueness of the solution is claimed. In an inner iterative procedure the axial node temperatures are found. For all physically realistic material properties the convergence is proved. In particular the assumptions needed for the Newton-Mysovskii theorem are secured. The metal mould PDE is locally solved by a series expansion. For particular material properties the same technique can be applied to the “solid” fluid.</p><p>In the circular plate application, comparisons with the commercial FEM-FD program Moldflow (Mfl) are made, on two Mfl-database materials, for which model parameters are estimated/adjusted. The resulting time evolutions of pressures and temperatures are analysed, as well as the radial and axial profiles of temperature and frozen layer. The greatest differences occur at the flow front, where Mfl neglects axial heat convection. The effects of using more and more complex material models are also investigated. Our method performance is reported.</p><p>In the polygonal star-shaped plate application a geometric cavity model is developed. Comparison runs with the commercial FEM-FD program Cadmould (Cmd) are performed, on two Cmd-database materials, in an equilateral triangular mould cavity, and materials model parameters are estimated/adjusted. The resulting average temperatures at the end of filling are compared, on rays of different angular deviation from the closest corner ray and on different concentric circles, using angular and axial (cavity-halves) symmetry. The greatest differences occur in narrow flow sectors, fatal for our 2D model for a material with non-realistic viscosity model. We present some colour plots, e.g. for the residence time.</p><p>The classical square-root increase by time of the frozen layer is used for extrapolation. It may also be part of the front model in the initial collision with the cold metal mould. An extension of the model is found which describes the radial profile of the frozen layer in the circular plate application accurately also close to the inlet.</p><p>The well-posedness of the corresponding linearized problem is studied, as well as the stability of the linearized FD-scheme.</p><br>Report code: LiU-TEK-LIC-2002:66.