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Dissertations / Theses on the topic 'Locally finite'
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1
Ersoy, Kivanc. "Centralizers Of Finite Subgroups In Simple Locally Finite Groups." Phd thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12610850/index.pdf.
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A group G is called locally finite if every finitely generated subgroup of G is finite. In this thesis we study the centralizers of subgroups in simple locally finite groups. Hartley proved that in a linear simple locally finite group, the fixed point of every semisimple automorphism contains infinitely many elements of
distinct prime orders. In the first part of this thesis, centralizers of finite abelian subgroups of linear simple locally finite groups are studied and the following result is proved: If G is a linear simple locally finite group and A is a finite d-abelian
subgroup consisting of semisimple elements of G, then C_G(A) has an infinite abelian subgroup isomorphic to the direct product of cyclic groups of order p_i for infinitely many distinct primes pi.
Hartley asked the following question: Let G be a non-linear simple locally finite group and F be any subgroup of G. Is CG(F) necessarily infinite? In the second part of this thesis, the following problem is studied: Determine the nonlinear
simple locally finite groups G and their finite subgroups F such that C_G(F) contains an infinite abelian subgroup which is isomorphic to the direct product of cyclic groups of order pi for infinitely many distinct primes p_i. We prove the following: Let G be a non-linear simple locally finite group with a split Kegel cover K and F be any finite subgroup consisting of K-semisimple elements of G. Then the centralizer C_G(F) contains an infinite abelian subgroup isomorphic to the direct product of cyclic groups of order p_i for infinitely many distinct primes
p_i.
2
Alam, Mahmood. "Cartan subalgebras of locally finite Lie algebras /." Aachen : Shaker, 2008. http://d-nb.info/992052076/04.
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3
Rowley, Jamie Robert Derek. "Inner ideals of simple locally finite Lie algebras." Thesis, University of Leicester, 2013. http://hdl.handle.net/2381/27828.
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Inner ideals of simple locally finite dimensional Lie algebras over an algebraically closed field of characteristic 0 are described. In particular, it is shown that a simple locally finite dimensional Lie algebra has a non-zero proper inner ideal if and only if it is of diagonal type. Regular inner ideals of diagonal type Lie algebras are characterized in terms of left and right ideals of the enveloping algebra. Regular inner ideals of finitary simple Lie algebras are described. Inner ideals of some finite dimensional Lie algebras are studied. Maximal inner ideals of simple plain locally finite dimensional Lie algebras are classified.
4
Duong, Hoan. "An invariant for locally finite dimensional semisimple algebras." Thesis, University of Ottawa (Canada), 1996. http://hdl.handle.net/10393/10016.
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Complete invariants were found for the category of unital direct limits of finite dimensional semisimple complex algebras and the category of unital direct limits of finite dimensional semisimple real algebras by G. A. Elliott ( (E)) and by K. R. Goodearl and D. E. Handelman ( (GH)) respectively. We are naturally led to consider similar complete invariants for other algebras of this type. For other fields, the situation is much more complicated, since the set of division rings containing a field F that is neither real closed nor algebraically closed is infinite (even ignoring the noncommutative ones). So let $\Omega=\{D\sb{i}\}$ be a finite set of finite dimensional division algebras, we shall only study the categories of unital direct limits of finite direct products of matrix algebras involving just this set of division rings. The conjecture of (GH) concerning a proposed complete invariant for direct limit algebras is simplified, and we show that this invariant (essentially a diagram of ordered $K\sb0$-groups) is complete, establishing the conjecture.
5
Ersoy, Kıvanç [Verfasser]. "Centralizers and Fixed Points of Automorphisms in Finite and Locally Finite Groups / Kıvanç Ersoy." Berlin : Freie Universität Berlin, 2020. http://nbn-resolving.de/urn:nbn:de:kobv:188-refubium-26475-9.
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6
Alam, Mahmood [Verfasser]. "Cartan Subalgebras of Locally Finite Lie Algebras / Mahmood Alam." Aachen : Shaker, 2008. http://d-nb.info/1161309519/34.
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7
Kechkar, Nasserdine. "Analysis and application of locally stabilised mixed finite element methods." Thesis, University of Manchester, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358327.
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8
Özyurt, Erdal. "Inert subgroups and centralizers of involutions in locally finite simple groups." Ankara : METU, 2003. http://etd.lib.metu.edu.tr/upload/1141546/index.pdf.
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Ozyurt, Erdal. "Inert Subgroups And Centralizers Of Involutions In Locally Finite Simple Groups." Phd thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/1141546/index.pdf.
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abstract
INERT SUBGROUPS AND CENTRALIZERS OF
INVOLUTIONS IN LOCALLY FINITE SIMPLE
GROUPS
¨Ozyurt, Erdal Ph. D., Department of Mathematics Supervisor: Prof. Dr. Mahmut Kuzucuo&
#728
glu September 2003, 68 pages A subgroup H of a group G is called inert if [H : H Hg] is finite for all g 2 G. A group is called totally inert if every subgroup is inert. Among the basic properties of inert subgroups, we prove the following. Let M be a maximal subgroup of a locally finite group G. If M is inert and abelian, then G is soluble with derived length at most 3. In particular, the given properties impose a strong restriction on the derived length of G. We also prove that, if the centralizer of every involution is inert in an infinite locally finite simple group G, then every finite set of elements of G can not be contained in a finite simple group. In a special case, this generalizes a Theorem of Belyaev&
#8211
Kuzucuo&
#728
glu&
#8211
Se¸
ckin, which proves that there exists no infinite locally finite totally inert simple group.
10
Fung, Kin-Hung. "Phononic band gap of locally resonant sonic materials with finite thickness /." View abstract or full-text, 2004. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202004%20FUNG.
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Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2004.Includes bibliographical references (leaves 73-74). Also available in electronic version. Access restricted to campus users.
11
Chan, Tsz Lung [Verfasser], and Reinhard [Akademischer Betreuer] Diestel. "Contractible edges in locally finite graphs / Tsz Lung Chan ; Betreuer: Reinhard Diestel." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://d-nb.info/114514263X/34.
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Chan, Tsz Lung Verfasser], and Reinhard [Akademischer Betreuer] [Diestel. "Contractible edges in locally finite graphs / Tsz Lung Chan ; Betreuer: Reinhard Diestel." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2017. http://nbn-resolving.de/urn:nbn:de:gbv:18-88445.
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13
Eastridge, Samuel Vance. "First Cohomology of Some Infinitely Generated Groups." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77517.
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The goal of this paper is to explore the first cohomology group of groups G that are not necessarily finitely generated. Our focus is on l^p-cohomology, 1 leq p leq infty, and what results regarding finitely generated groups change when G is infinitely generated. In particular, for abelian groups and locally finite groups, the l^p-cohomology is non-zero when G is countable, but vanishes when G has sufficient cardinality. We then show that the l^infty-cohomology remains unchanged for many classes of groups, before looking at several results regarding the injectivity of induced maps from embeddings of G-modules. We present several new results for countable groups, and discuss which results fail to hold in the general uncountable case. Lastly, we present results regarding reduced cohomology, including a useful lemma extending vanishing results for finitely generated groups to the infinitely generated case.Ph. D.
14
Okman, Oya. "Free Forming Of Locally Induction Heated Specimens." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605951/index.pdf.
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Hot forming is highly utilized in manufacturing of complex shapes. Relatively low flow stresses of materials at elevated temperatures provide ease of manufacturing. On the other side, the current trend is to replace hot forming with cold forming due to the superior mechanical properties and higher dimensional accuracy of the products and less energy consumption. However, cold forming requires high tooling costs and forming loads. In this study, a new process is proposed for production of complex shaped products where the disadvantages of both of the alternatives are tried to be minimized. The basic idea is to control the mode of deformation by heating the specimen locally prior to forming. Electromagnetic induction is used for local heating. Numerical simulations are carried out by finite element method (FEM) for further investigation on the effect of parameters. Thermo-mechanical analysis of heat diffusion and upsetting is supported by electromagnetic analysis of induction heating. The failure modes and operational window of the novel process is established. Conclusions are drawn on the applicability of the process and the effect of process parameters on the efficiency.
15
Hristova, Elitza [Verfasser]. "Branching laws for tensor modules over classical locally finite lie algebras / Elitza Hristova." Bremen : IRC-Library, Information Resource Center der Jacobs University Bremen, 2013. http://d-nb.info/1037012410/34.
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Jung, Michael, Aleksandr M. Matsokin, Sergey V. Nepomnyaschikh, and Yu A. Tkachov. "Multilevel preconditioning operators on locally modified grids." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601671.
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Systems of grid equations that approximate elliptic boundary value problems on locally modified grids are considered. The triangulation, which approximates the boundary with second order of accuracy, is generated from an initial uniform triangulation by shifting nodes near the boundary according to special rules. This "locally modified" grid possesses several significant features: this triangulation has a regular structure, the generation of the triangulation is rather fast, this construction allows to use multilevel preconditioning (BPX-like) methods. The proposed iterative methods for solving elliptic boundary value problems approximately are based on two approaches: The fictitious space method, i.e. the reduction of the original problem to a problem in an auxiliary (fictitious) space, and the multilevel decomposition method, i.e. the construction of preconditioners by decomposing functions on hierarchical grids. The convergence rate of the corresponding iterative process with the preconditioner obtained is independent of the mesh size. The construction of the grid and the preconditioning operator for the three dimensional problem can be done in the same way.
17
Ozmen, Murat. "Free Forming Of Locally Laser Heated Parts." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/12605952/index.pdf.
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As metals have high formability at elevated temperatures, hot forming is preferred and widely used in manufacturing of complicated geometries. The term hot forming is usually used if the whole workpiece is processed at elevated temperatures. However, for certain products high formability is
required only locally. Forming by local heating is proposed to provide ease of manufacturing of local forms on the workpiece. Also, tools can be simplified by this method. In this study, local laser heating procedures are applied to obtain local forms on cylindrical bulk metal products in a single step. Locally heated workpieces are formed between two flat dies. Both solid and hollow products have been investigated experimentally and by finite element modeling. The experimental studies and finite element analyses are done simultaneously in order to obtain optimum local deformation characteristics. Three different materials together with different initial geometries and various local laser-heating procedures are applied to search for the process window. The limits of applicability are determined and examples of application are supplied.
18
Xu, Jing. "On closures of finite permutation groups." University of Western Australia. School of Mathematics and Statistics, 2006. http://theses.library.uwa.edu.au/adt-WU2006.0023.
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[Formulae and special characters in this field can only be approximated. See PDF version for accurate reproduction] In this thesis we investigate the properties of k-closures of certain finite permutation groups. Given a permutation group G on a finite set Ω, for k ≥ 1, the k-closure G(k) of G is the largest subgroup of Sym(Ω) with the same orbits as G on the set Ωk of k-tuples from Ω. The first problem in this thesis is to study the 3-closures of affine permutation groups. In 1992, Praeger and Saxl showed if G is a finite primitive group and k ≥ 2 then either G(k) and G have the same socle or (G(k),G) is known. In the case where the socle of G is an elementary abelian group, so that G is a primitive group of affine transformations of a finite vector space, the fact that G(k) has the same socle as G gives little information about the relative sizes of the two groups G and G(k). In this thesis we use Aschbacher’s Theorem for subgroups of finite general linear groups to show that, if G ≤ AGL(d, p) is an affine permutation group which is not 3-transitive, then for any point α ∈ Ω, Gα and (G(3) ∩ AGL(d, p))α lie in the same Aschbacher class. Our results rely on a detailed analysis of the 2-closures of subgroups of general linear groups acting on non-zero vectors and are independent of the finite simple group classification. In addition, modifying the work of Praeger and Saxl in [47], we are able to give an explicit list of affine primitive permutation groups G for which G(3) is not affine. The second research problem is to give a partial positive answer to the so-called Polycirculant Conjecture, which states that every transitive 2-closed permutation group contains a semiregular element, that is, a permutation whose cycles all have the same length. This would imply that every vertex-transitive graph has a semiregular automorphism. In this thesis we make substantial progress on the Polycirculant Conjecture by proving that every vertex-transitive, locally-quasiprimitive graph has a semiregular automorphism. The main ingredient of the proof is the determination of all biquasiprimitive permutation groups with no semiregular elements. Publications arising from this thesis are [17, 54].
19
Eastridge, Samuel Vance. "First l^2-Cohomology Groups." Thesis, Virginia Tech, 2015. http://hdl.handle.net/10919/52952.
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We want to take a look at the first cohomology group H^1(G, l^2(G)), in particular when G is locally-finite. First, though, we discuss some results about the space H^1(G, C G) for G locally-finite, as well as the space H^1(G, l^2(G)) when G is finitely generated. We show that, although in the case when G is finitely generated the embedding of C G into l^2(G) induces an embedding of the cohomology groups H^1(G, C G) into H^1(G, l^2(G)), when G is countably-infinite locally-finite, the induced homomorphism is not an embedding. However, even though the induced homomorphism is not an embedding, we still have that H^1(G, l^2(G)) neq 0 when G is countably-infinite locally-finite. Finally, we give some sufficient conditions for H^1(G,l^2(G)) to be zero or non-zero.Master of Science
20
Thomas, Craig George. "A locally conservative Galerkin (LCG) finite element method for convection-diffusion and Navier-Stokes equations." Thesis, Swansea University, 2006. https://cronfa.swan.ac.uk/Record/cronfa42342.
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In this thesis, an element-wise locally conservative Galerkin (LCG) finite element method is presented. The LCG method has been shown here to be successful in solving equations of scalar-transport, and the incompressible Navier-Stokes equations. The LCG approach facilitates an element-by-element solution and obtains a continuous and unique nodal solution from the surrounding element contributions, via averaging. A simple numerical flux establishes continuity at the edges between neighbouring elements. This allows the system of discrete equations to be solved over each elemental sub-domain, greatly simplifying the solution procedure. The method explicitly establishes local elementwise conservation, and after the averaging procedure a residual flux appears on the global boundary. It is this flux which gives the LCG method global conservation, regardless of prescribed boundary conditions. Aspects research are: the mathematical formulation; explicit and implicit discretisations; edge flux calculation procedures; development and implementation of Petrov-Galerkin and characteristic based methods; and finally matrix-free LCG methods for steady and unsteady incompressible flows. Evaluation of all the proposed LCG methods has been given, showing the methods to be accurate and robust.
21
Derakhshan, Jamshid. "Problems on nilpotency and local finiteness in infinite groups and infinite dimensional algebras." Thesis, University of Oxford, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362007.
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Hu, Chao. "Locally enhanced voronoi cell finite element model (LE-VCFEM) for ductile fracture in heterogeneous cast aluminum alloys." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1199209208.
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Hemmi, Tadashi. "Locally one dimensional finite difference time domain method with frequency dependent media for three dimensional biomedical applications." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/locally-one-dimensional-finite-difference-time-domain-method-with-frequency-dependent-media-for-three-dimensional-biomedical-applications(f5fc769a-7dc4-4cce-80f0-755054cb4bab).html.
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The finite difference time domain (FDTD) method is commonly used for numerical simulations of the electromagnetic wave propagation in time domain. The FDTD method is easy to implement and the computational results are highly relevant to the analytical solution, so that the FDTD method is applied to variety application problems. However, the computational efficiency of the FDTD method is constrained by the upper limit of the temporal discretisation. The Courant Friedrich Lewy (CFL) stability condition limits the time step for the computation of the FDTD method, so that if the spatial discretisation of the computation is set to be small in order to obtain high accurate results, the size of the temporal discretisation need to be satisfy the CFL stability condition. The locally one dimensional FDTD (LOD-FDTD) method is unconditionally stable. The time step and the spatial step can be independently chosen for the computation of the LOD-FDTD method. The arithmetic operations of the LOD-FDTD method is fewer than that of the other implicit FDTD method, such as the Crank Nicolson FDTD (CN-FDTD) method and the alternating direction implicit FDTD (ADI-FDTD) method. Although the implementation of the LOD-FDTD method is simpler than that of the ADI-FDTD method,the numerical error in the computational results of the LOD-FDTD method is equivalent to that in the computational results of the ADI-FDTD method. In this thesis, a new three dimensional (3D) frequency dependent (FD) LOD-FDTD method is proposed. The one pole Debye model is incorporated into the 3D-FD-LOD-FDTD method in order to deal with practical applications. The proposed method is implemented in Fortran 90 and parallelised with OpenMP. A simulation model of the human phantom is developed in the 3D-FD-LOD-FDTD method with fine structures and frequency dependent dielectric properties of the human tissues, and numerical simulation of electromagnetic wave propagation inside the human head is shown.
24
Guzainuer, Maimaitiyiming. "Boundary Summation Equation Preconditioning for Ordinary Differential Equations with Constant Coefficients on Locally Refined Meshes." Thesis, Linköpings universitet, Matematiska institutionen, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-102573.
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This thesis deals with the numerical solution of ordinary differential equations (ODEs) using finite difference (FD) methods. In particular, boundary summation equation (BSE) preconditioning for FD approximations for ODEs with constant coefficients on locally refined meshes is studied. Firstly, the BSE for FD approximations of ODEs with constant coefficients is derived on a locally refined mesh. Secondly, the obtained linear system of equations are solved by the iterative method GMRES. Then, the arithmetic complexity and convergence rate of the iterative solution of the BSE formulation are discussed. Finally, numerical experiments are performed to compare the new approach with the FD approach. The results show that the BSE formulation has low arithmetic complexity and the convergence rate of the iterative solvers is fast and independent of the number of grid points.
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Igreja, Iury Higor Aguiar da. "Locally perturbative multiscale methods for ionic solute transport in clayly soils." Laboratório Nacional de Computação Científica, 2010. http://www.lncc.br/tdmc/tde_busca/arquivo.php?codArquivo=206.
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This work aims at developing computational models capable of furnishing more realistic and less costly computationally for the problem of electrokinetic remediation of polluted clayey soils. Innovative results are obtained by improving the multiscale models previously developed by Lima and co-workers through the construction of perturbations of the local microscopic problems in conjuction with more realistic boundary conditions at the electrodes and with the development of precise estimates for the assymptotic behavior of the macroscopic solution. Considering the aliance of such techniques within the framework of the homogenization method of periodic structures we discretize the macroscopic model by the finite element method numerical simulations of an electroosmose experiment capable of predicting more realistic scenarios of electrokinetic remediation.Este trabalho objetiva o desenvolvimento de modelos computacionais capazes de construir simulações numéricas mais realistas e menos custosas computacionalmente para o problema de descontaminação de solos argilosos por técnicas de eletrocinética. Resultados inovadores são obtidos aprimorando-se os modelos multi-escala desenvolvidos anteriormente por Lima e colaboradores via construção de soluções perturbativas dos problemas locais microscópicos aliada à condições de contorno mais realistas nos eletrodos e ao desenvolvimento de estimativas precisas para o comportamento assintótico da solução macroscópica. Por intermédio da conjunção destas técnicas imersas no contexto da teoria de homogeneização de estruturas periódicas discretizamos o modelo macroscópico pelo método dos elementos finitos e construimos simulações numéricas de um experimento de eletroosmose capazes de predizer cenários mais realistas em eletrorremediação de solos.
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Aland, Sebastian, Sabine Egerer, John Lowengrub, and Axel Voigt. "Diffuse interface models of locally inextensible vesicles in a viscous fluid." Elsevier, 2014. https://htw-dresden.qucosa.de/id/qucosa%3A32307.
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We present a new diffuse interface model for the dynamics of inextensible vesicles in a viscous fluid with inertial forces. A new feature of this work is the implementation of the local inextensibility condition in the diffuse interface context. Local inextensibility is enforced by using a local Lagrange multiplier, which provides the necessary tension force at the interface. We introduce a new equation for the local Lagrange multiplier whose solution essentially provides a harmonic extension of the multiplier off the interface while maintaining the local inextensibility constraint near the interface. We also develop a local relaxation scheme that dynamically corrects local stretching/compression errors thereby preventing their accumulation. Asymptotic analysis is presented that shows that our new system converges to a relaxed version of the inextensible sharp interface model. This is also verified numerically. To solve the equations, we use an adaptive finite element method with implicit coupling between the Navier-Stokes and the diffuse interface inextensibility equations. Numerical simulations of a single vesicle in a shear flow at different Reynolds numbers demonstrate that errors in enforcing local inextensibility may accumulate and lead to large differences in the dynamics in the tumbling regime and smaller differences in the inclination angle of vesicles in the tank-treading regime. The local relaxation algorithm is shown to prevent the accumulation of stretching and compression errors very effectively. Simulations of two vesicles in an extensional flow show that local inextensibility plays an important role when vesicles are in close proximity by inhibiting fluid drainage in the near contact region.
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De, Saedeleer Julie. "The residually weakly primitive and locally two-transitive rank two geometries for the groups PSL(2, q)." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210037.
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The main goal of this thesis is a contribution to the classification of all incidence geometriesof rank two on which some group PSL(2,q), q a prime power, acts flag-transitively.
Actually we require that the action be RWPRI (residually weakly primitive) and (2T)1
(doubly transitive on every residue of rank one). In fact our definition of RWPRI requires
the geometry to be firm (each residue of rank one has at least two elements) and RC
(residually connected).
The main goal is achieved in this thesis.
It is stated in our "Main Theorem". The proof of this theorem requires more than 60pages.
Quite surprisingly, our proof in the direction of the main goal uses essentially the classification
of all subgroups of PSL(2,q), a famous result provided in Dickson’s book "Linear groups: With an exposition of the Galois field theory", section 260, in which the group is called Linear Fractional Group LF(n, pn).
Our proof requires to work with all ordered pairs of subgroups up to conjugacy.
The restrictions such as RWPRI and (2T)1 allow for a complete analysis.
The geometries obtained in our "Main Theorem" are bipartite graphs; and also locally 2-arc-transitive
graphs in the sense of Giudici, Li and Cheryl Praeger. These graphs are interesting in their own right because of
the numerous connections they have with other fields of mathematics.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished
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Vittoz, Louis. "Contributions au développement d’un solveur volumes finis sur grille cartésienne localement raffinée en vue d’application à l’hydrodynamique navale." Thesis, Ecole centrale de Nantes, 2018. http://www.theses.fr/2018ECDN0020/document.
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L’objectif de cette thèse est de répondre au besoin d’accélérer la restitution des résultats de calcul d’un code CFD pour la simulation d’écoulements hydrodynamiques quasi-incompressibles. Ce code présente l’originalité de résoudre explicitement les équations de Navier-Stokes sous l’hypothèse de faible compressibilité avec des schémas numériques d’ordre élevé. Les développements effectués visent à réduire les temps de calcul à précision équivalente.Une première partie est consacrée à l’implémentation d’une formulation purement incompressible avec une résolution implicite de la pression par un schéma de projection. La formulation incompressible autorise des pas de temps plus grand en s’affranchissant de la vitesse du son, mais au prix d’une algorithmique plus complexe et de la nécessité de résoudre un système linéaire. La comparaison des deux formulations,faiblement-compressible et incompressible, tend à montrer la pertinence du schéma de projection pour les écoulements laminaires instationnaires.Un deuxième axe de développement a consisté en la proposition d’une amélioration de la méthode de frontière immergée initialement présente dans le code.Si les résultats obtenus ne sont pas encore pleinement satisfaisants, ils montrent que la montée en ordre d’une méthode de frontière immergée peut être moins contraignante en formulation incompressible.Enfin la dernière partie traite de l’immersion rapide et robuste de géométries complexes telles qu’elles peuvent être rencontrées dans l’industrie. La localisation géométrique par arbre octal permet d’évaluer rapidement une fonction de distance signée indispensable pour la méthode de frontière immergéeAn original strategy to address hydrodynamic flow was recently proposed through a high-order weakly-compressible Cartesian grid approach. The method is based on a fully-explicit temporal scheme for solving the Navier-Stokes equations. The present thesis aims to reduce the computational time required to obtain the results without deteriorating the accuracy.A first part is dedicated to the implementation of a truly incompressible formulation with an implicit solution for the pressure field through a projection scheme. The incompressible solver allows larger time step size for time integration since the speed of sound tends to infinity. In return the algorithms are no longer straight forward and a linear system has to be solved through the Pressure Poisson Equation. Comparisons carried out between both formulations show that the projection scheme can be better adapted to efficiently simulate unsteady viscous flows. Then an improvement of the immersed boundary method has been proposed. Results are not fully satisfactory for now. However, it seems easier to develop a numerical scheme for the incompressible approach rather than the weakly-compressible one.Finally, the last part addresses the setup up of complex triangulations in immersed boundary simulations. A fast and robust procedure is developed for distance computation with an octree data structure
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Paquet, Daniel. "Adaptive Multi-level Model for Multi-scale Ductile Fracture Analysis in Heterogeneous Aluminum Alloys." The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1324565883.
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Lehoťák, Roman. "Návrh betonové konstrukce s ohledem na požární odolnost." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2021. http://www.nusl.cz/ntk/nusl-444631.
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The diploma thesis deals with the analysis of internal forces and the design of the reinforcement of a reinforced concrete monolithic slab, a reinforcing wall and a column in the 1st floor of a dairy hall building. The fire resistance of selected structures was taken into account during dimensioning. The calculation of the internal forces was performed by the finite element method in Dlubal RFEM 5.24.
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Lozano, Bagén Toni. "On the exoticness of some new p-local compact groups." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/385105.
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En 2003, Broto-Levi-Oliver van introduir el concepte de grup p-local finit, el qual és una generalització dels espais classificadors de grups finits p-completats. Més tard, els mateixos autors van introduir també el concepte de grup p-local compacte, el qual és una generalització dels espais classificadors de grups de Lie p-completats i dels grups p-compactes. Mentre que el concepte de grup p-local finit exòtic està clarament definit, en el cas compacte hi ha vàries famílies de grups que donen lloc a grups p-locals compactes, desdibuixant així la noció d'exoticitat.
En aquesta tesi construim nous exemples de grups p-locals finits exòtics per a cada p >= 5. A més, demostrem que aquests nous exemples són simples en el sentit de que no contenen cap subsistema normal propi no trivial.
Llavors, desenvolupem la teoria dels límits de sistemes de fusió. Demostrem que, per a tota família de sistemes de fusió satisfent certes propietats de compatibiliat, podem construir un sistema de fusió relacionat sobre un grup p-toral discret. A més, provem que aquesta construcció del límit coincideix amb el límit directe des d'un punt de vista categòric sota hipòtesis de saturació.
Utilitzant els nous exemples de grups p-locals finits per a p >= 5, així com també altres famílies descobertes per Broto-Levi-Oliver i Díaz-Ruiz-Viruel, apliquem la construcció del límit per a obtenir dos nous exemples de sistemes de fusió sobre grups p-torals discrets per a cada p >= 5 i un nou exemple per a p = 3.
Un cop tenim els nous sistemes de fusió, generalitzem un criteri de saturació conegut per a grups p-locals finits al cas compacte. Llavors, utilitzem aquest criteri per demostrar la saturació dels nous exemples que hem creat, donant lloc així a nous exemples de grups p-locals compactes.
Finalment, demostrem que tant el nou exemple de grup 3-local compacte com els dous nous exemples de grups p-locals compactes per a p >= 5 no es poden realitzar amb grups de Lie compactes ni amb grups p-compactes.In 2003, Broto-Levi-Oliver introduced the concept of p-local finite group, which is a generalization for p-completed classifying spaces of finite groups. Later, the same authors introduced also the notion of p-local compact group, which is a generalization for p-completed classifying spaces of compact Lie groups and p-compact groups. While the concept of exotic p-local finite group is clearly defined, in the compact case there are several families of groups which give rise to p-local compact groups, blurring this way the notion of exoticness. In this thesis we construct new examples of exotic p-local finite groups for every p >= 5. Moreover, we prove that these new examples are simple in the sense that they contain no proper nontrivial normal subsystems. Then, we develop the theory of limits of fusion systems. We prove that, for any family of fusion systems satisfying certain compatibility properties, we can construct a related fusion system over a discrete p-toral group. Moreover, we prove that this limit construction coincides with the direct limit from a categorical point of view under saturation hypothesis. Using the new examples of p-local finite groups for p >= 5, as well as other families of examples discovered by Broto-Levi-Oliver and Díaz-Ruiz-Viruel, we apply the limit construction to produce two new examples of fusion systems over discrete p-toral groups for each p >= 5 and one new example for p = 3. Once we have the new saturated fusion systems, we generalize a saturation criterion known for p-local finite groups to the compact case. Then, we use this criterion to prove the saturation of the new examples we have created, giving rise in this way to new examples of p-local compact groups. Finally, we prove that neither the new example of 3-local compact group nor the new two examples of p-local compact groups for p >= 5 can be realized by compact Lie groups or by p-compact groups.
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Bird, Gregory David. "Linear and Nonlinear Dimensionality-Reduction-Based Surrogate Models for Real-Time Design Space Exploration of Structural Responses." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8653.
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Design space exploration (DSE) is a tool used to evaluate and compare designs as part of the design selection process. While evaluating every possible design in a design space is infeasible, understanding design behavior and response throughout the design space may be accomplished by evaluating a subset of designs and interpolating between them using surrogate models. Surrogate modeling is a technique that uses low-cost calculations to approximate the outcome of more computationally expensive calculations or analyses, such as finite element analysis (FEA). While surrogates make quick predictions, accuracy is not guaranteed and must be considered. This research addressed the need to improve the accuracy of surrogate predictions in order to improve DSE of structural responses. This was accomplished by performing comparative analyses of linear and nonlinear dimensionality-reduction-based radial basis function (RBF) surrogate models for emulating various FEA nodal results. A total of four dimensionality reduction methods were investigated, namely principal component analysis (PCA), kernel principal component analysis (KPCA), isometric feature mapping (ISOMAP), and locally linear embedding (LLE). These methods were used in conjunction with surrogate modeling to predict nodal stresses and coordinates of a compressor blade. The research showed that using an ISOMAP-based dual-RBF surrogate model for predicting nodal stresses decreased the estimated mean error of the surrogate by 35.7% compared to PCA. Using nonlinear dimensionality-reduction-based surrogates did not reduce surrogate error for predicting nodal coordinates. A new metric, the manifold distance ratio (MDR), was introduced to measure the nonlinearity of the data manifolds. When applied to the stress and coordinate data, the stress space was found to be more nonlinear than the coordinate space for this application. The upfront training cost of the nonlinear dimensionality-reduction-based surrogates was larger than that of their linear counterparts but small enough to remain feasible. After training, all the dual-RBF surrogates were capable of making real-time predictions. This same process was repeated for a separate application involving the nodal displacements of mode shapes obtained from a FEA modal analysis. The modal assurance criterion (MAC) calculation was used to compare the predicted mode shapes, as well as their corresponding true mode shapes obtained from FEA, to a set of reference modes. The research showed that two nonlinear techniques, namely LLE and KPCA, resulted in lower surrogate error in the more complex design spaces. Using a RBF kernel, KPCA achieved the largest average reduction in error of 13.57%. The results also showed that surrogate error was greatly affected by mode shape reversal. Four different approaches of identifying reversed mode shapes were explored, all of which resulted in varying amounts of surrogate error. Together, the methods explored in this research were shown to decrease surrogate error when performing DSE of a turbomachine compressor blade. As surrogate accuracy increases, so does the ability to correctly make engineering decisions and judgements throughout the design process. Ultimately, this will help engineers design better turbomachines.
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LIMA, Márcio Dias de. "Sobre Centralizadores de Automorfismos Coprimos em Grupos Profinitos e Álgebras de Lie." Universidade Federal de Goiás, 2011. http://repositorio.bc.ufg.br/tede/handle/tde/1947.
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Previous issue date: 2011-06-27A be an elementary abelian group of order q2, where q a prime number. In this paper we will study the influence of centering on the structure of automorphism groups profinitos in this sense if A acting as a coprime group of automorphisms on a group profinito G and CG(a) is periodic for each a 2 A#, then we will show that G is locally finite. It will be demonstrated also the case where A acts as a group of automorphisms of a group pro-p of G
Sejam A um grupo abeliano elementar de ordem q2, onde q um número primo. Neste trabalho estudamos a influência dos centralizadores de automorfismos na estrutura dos grupos profinitos, neste sentido se A age como um grupo de automorfismos coprimos sobre um grupo profinito G e que CG(a) é periódico para cada a 2 A#, então mostraremos que G é localmente finito. Será demonstrado também o caso onde A age como um grupo de automorfismos sobre um grupo pro-p de G.
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Ballantyne, John Joseph. "Local fusion graphs of finite groups." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/local-fusion-graphs-of-finite-groups(131e11a2-2ca6-478e-b8d9-119a78de8935).html.
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Let G be a group, with X a G-conjugacy class of involutions. The local fusion graph F(G,X) has X as its vertex set, with vertices x, y in X joined by an edge if, and only if, x is not equal to y and the order of the product xy is odd. In this thesis we study these, and other related graphs, for a variety of finite groups, paying particular attention to the cases where G is a finite group. We also present a computational algorithm regarding centralisers of involutions, which makes use of local fusion graphs.
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Garbin, Turpaud Fernando, and Pachas Ángel Alfredo Lévano. "Higher-order non-local finite element bending analysis of functionally graded." Bachelor's thesis, Universidad Peruana de Ciencias Aplicadas (UPC), 2019. http://hdl.handle.net/10757/626024.
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La teoría de vigas de Timoshenko TBT y una teoría de alto orden IFSDT son formuladas utilizando las ecuaciones constitutivas no locales de Eringen. Se utilizaron ecuaciones constitutivas en 3D en el modelo IFSDT. Se utilizó una variación del material con el uso de materiales funcionalmente graduados a lo largo del peralte de una viga de sección rectangular. El principio de trabajos virtuales utilizado y ejemplos numéricos fueron presentados para comparar ambas teorías de vigas.Timoshenko Beam Theory (TBT) and an Improved First Shear Deformation Theory (IFSDT) are reformulated using Eringen’s non-local constitutive equations. The use of 3D constitutive equation is presented in IFSDT. A material variation is made by the introduction of FGM power law in the elasticity modulus through the height of a rectangular section beam. The virtual work statement and numerical results are presented in order to compare both beam theories.
Tesis
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Hons, Filip. "Železobetonová skeletová konstrukce." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227233.
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Master´s thesis focuses on the design of monolithic reinforced concrete structures storey hose which consist of 2 underground and 6 floors. This project deals whit two different boards, board over ground floor and over second floor, as well as three pillars supporting board, separate staircase placed in a reinforced core, base plate. All calculations are done according to applicable standards, mainly according to ČSN EN 1992-1-1.
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Houston, Kevin. "Local topology of finite complex analytic maps." Thesis, University of Warwick, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.337157.
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Fúquene, Patiño Jairo A. "Finite mixture modeling with non-local priors." Thesis, University of Warwick, 2018. http://wrap.warwick.ac.uk/111373/.
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Choosing the number of mixture components remains a central but elusive challenge. Traditional model selection criteria can be either overly liberal or conservative when enforcing parsimony. They may also result in poorly separated components of limited practical use. In this thesis, the term parsimony refers to selecting a simpler model by enforcing a separation between the models under consideration, and the term sparsity refers to the ability of penalizing overfitted models leading to well-separated components with non-negligible weight, interpretable as distinct subpopulations. Non-local priors (NLPs) are a family of distributions that encourage parsimony by enforcing a separation between the models under consideration. In this thesis we investigate the use of NLPs to choose the number of components in mixture models. Our main contributions are proposing the use of non-local priors (NLPs) to select the number of components, characterizing the properties of the associated inference (in particular, improved sparsity) and proposing tractable expressions suitable for prior elicitation purposes, simpler and computationally efficient algorithms and practical applications. Chapter 2 develops the theoretical framework. We present NLPs in the context of mixtures and show how they lead to well-separated components that have non-negligible weight, hence interpretable as distinct subpopulations. Moreover we formulate a general NLP class, propose a particular choice leading to tractable expressions and give a theoretical characterization of the sparsity induced by NLPs for choosing the number of mixture components. Although the framework is generic we fully develop multivariate Normal, Binomial and product Binomial mixtures based on a family of exchangeable moment priors. Chapter 3 presents the prior computation and elicitation. We suggest default prior settings based on detecting multi-modal Normal and T mixtures, and minimal informativeness for categorical outcomes where multi-modality is not a natural consideration. The theory and underlying principles in this thesis hold more generally as outlined in Chapter 2, however. Chapter 4 presents the computational framework for model selection and fitting. We propose simple algorithms based on Markov chain Monte Carlo methods and Expectation Maximization algorithms to obtain the integrated likelihood and parameter estimates. Chapters 5-7 contain the simulation studies and applications. In Chapter 5 we compare the performance of our proposal to its local prior counterpart as well as the Bayesian Information Criterion (BIC), the singular Bayesian Information Criterion (sBIC) and the Akaike Information Criterion (AIC). Our results show a serious lack of sensitivity of the Bayesian information criterion (BIC) and insufficient parsimony of the AIC and the local prior counterpart to our formulation. The singular BIC behaved like the BIC in some examples and the AIC in others. In Chapter 6 we explore a computational fast non-local model selection cri- teria and propose a new computational strategy that provides a direct connection between cluster occupancies and Bayes factors with the advantage that Bayes factors allow for more general model comparisons (for instance equal vs unequal covariances in Normal mixtures). This new computational strategy is helpful to discard unoccupied clusters in overfitted mixtures and we remark that the result has interest beyond purely computational purposes, e.g. to set thresholds on empty cluster probabilities in overfitted mixtures. In Chapter 7 we present the applications of this thesis and also offer comparisons to overfitted and repulsive overfitted mixtures. In most examples their performance was competitive but depended on setting the prior parameters adequately to prevent the appearance of spurious components. The number of components inferred under NLPs was closer to the true number (when this was known) and remained robust to prior parameter changes, provided these remain in the range of recommended defaults. In Chapter 8 we have the conclusions and some possible future directions of this work. Finally, in Appendix A we present the proofs of Theorem 1 as well as auxiliary lemmas and corollaries. Appendix B shows the MCMC diagnostics. Appendix C presents the main probability density functions used throughout this thesis.
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Ragnarsson, KaÅ i. 1977. "Frobenius transfers and p-local finite groups." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32245.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mathematics, 2004.Includes bibliographical references (p. 43-44).
In this thesis we explore the possibility of defining the p-local finite groups of Broto, Levi and Oliver in terms of their classifying spaces. More precisely, we consider the question posed by Haynes Miller, whether an equivalent theory can be recovered by studying maps f: BS --> X from the classifying space of a finite p-group S to a p-complete space X equipped with a stable retract t satisfying a form of Frobenius reciprocity. In the case where S is elementary abelian, we answer this question in the affirmative, by showing that under some finiteness conditions such a triple (f, t, X) does indeed induce a p-local finite group over S. We also discuss the converse in some detail for general S.
by KaÅi Ragnarsson.
Ph.D.
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Ahlbert, Gabriella. "Method Evaluation of Global-Local Finite Element Analysis." Thesis, Linköpings universitet, Hållfasthetslära, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-78103.
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When doing finite element analysis upon the structure of Saab’s aeroplanes a coarse global model of mainly shell elements is used to determine the load distribution for sizing the structure. At some parts of the aeroplane it is however desirable to implement a more detailed analysis. These areas are usually modelled with solid elements; the problem of connecting the fine local solid elements to the coarse global model will shell elements then arises. This master thesis is preformed to investigate possible Global-Local methods to use for the structural analysis on Gripen. First a literature study of current methods on the market is made, thereafter a few methods are implemented on a generic test structure and later on also tested on a real detail of Gripen VU. The methods tested in this thesis are Mesh refinement in HyperWorks, RBE3 in HyperWorks, Glue in MSC Patran/Nastran and DMIG in MSC Nastran. The software is however not evaluated in this thesis, and a further investigation is recommended to find the most fitting software for this purpose. All analysis are performed with linear assumptions. Mesh refinement is an integrated technique where the elements are gradually decreasing in size. Per definition, this technique cannot handle gaps, but it has almost identical results to the fine reference model. RBE3 is a type of rigid body elements with zero stiffness, and is used as an interface element. RBE3 is possible to use to connect both Shell-To-Shell and Shell-To-Solid, and can handle offsets and gaps in the boundary between the global and local model. Glue is a contact definition and is also available in other software under other names. The global respectively the local model is defined as contact bodies and a contact table is used to control the coupling. Glue works for both Shell-To-Shell and Shell-To-Solid couplings, but has problem dealing with offsets and gaps in the boundary between the global and local model. DMIG is a superelement technique where the global model is divided into smaller sub-models which are mathematically connected. DMIG is only possible to use when the nodes on the boundary on the local model have the same position as the nodes at the boundary of the global model. Thus, it is not possible to only use DMIG as a Global-Local method, but can advantageously be combined with other methods. The results indicate that the preferable method to use for Global-Local analysis is RBE3. To decrease the size of the files and demand of computational power, RBE3 can be combined with a superelement technique, for example DMIG. Finally, it is important to consider the size of the local model. There will inevitably be boundary effect when performing a Global-Local analysis of the suggested type, and it is therefore important to make the local model big enough so that the boundary effects have faded before reaching the area of interest.
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Walton, James Jonathan. "Pattern-equivariant homology of finite local complexity patterns." Thesis, University of Leicester, 2014. http://hdl.handle.net/2381/28923.
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This thesis establishes a generalised setting with which to unify the study of finite local complexity (FLC) patterns. The abstract notion of a pattern is introduced, which may be seen as an analogue of the space group of isometries preserving a tiling but where, instead, one considers partial isometries preserving portions of it. These inverse semigroups of partial transformations are the suitable analogue of the space group for patterns with FLC but few global symmetries. In a similar vein we introduce the notion of a collage, a system of equivalence relations on the ambient space of a pattern, which we show is capable of generalising many constructions applicable to the study of FLC tilings and Delone sets, such as the expression of the tiling space as an inverse limit of approximants. An invariant is constructed for our abstract patterns, the so called patternequivariant (PE) homology. These homology groups are defined using infinite singular chains on the ambient space of the pattern, although we show that one may define cellular versions which are isomorphic under suitable conditions. For FLC tilings these cellular PE chains are analogous to the PE cellular cochains [47]. The PE homology and cohomology groups are shown to be related through Poincare duality. An efficient and highly geometric method for the computation of the PE homology groups for hierarchical tilings is presented. The rotationally invariant PE homology groups are shown not to be a topological invariant for the associated tiling space and seem to retain extra information about global symmetries of tilings in the tiling space. We show how the PE homology groups may be incorporated into a spectral sequence converging to the Cech cohomology of the rigid hull of a tiling. These methods allow for a simple computation of the Cech cohomology of the rigid hull of the Penrose tilings.
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Vidussoni, Marco A. "Global-local finite element analysis of laminated composites." Thesis, Virginia Tech, 1988. http://hdl.handle.net/10919/45966.
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A Global-Local finite element approach was used to investigate the interlaminar stresses in laminated composite plates with a central circular hole. Detailed solutions were sought for the interlaminar normal stress distributions close to the free straight edge of the plate as well as around the edge of the hole. The Global model was analyzed as a two-dimensional problem. The displacements obtained a distance away from the regions of interest in the two-dimensional model were used as imposed boundary conditions to the three-dimensional models of the edges.
The results obtained were found to be accurate, thus demonstrating the validity and strength of the Global-Local technique. The results further concluded that for symmetric cross-ply laminated plates with large central circular holes, the interlaminar normal stresses at the free edges are affected to a small degree by the size of the hole.
The CSM Testbed and ANISAP were the two finite element analysis programs used throughout this investigation. The CSM Testbed element library was augmented with 16, 20, 24 and 32 node displacement formulation based elements which were implemented as Experimental elements.
Master of Science
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Drouet, Guillaume. "Méthode locale de type mortar pour le contact dans le cas de maillages incompatibles de degré élevé." Thesis, Toulouse 3, 2015. http://www.theses.fr/2015TOU30142/document.
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Dans cette thèse, nous développons une méthode locale de type "mortar" pour traiter le problème de contact avec maillages incompatibles de manière optimale dans un code de calcul par éléments finis de niveau industriel. Dans la première partie de la thèse, nous introduisons le cadre mathématique de la méthode intitulée "Local Average Contact" (LAC). Cette approche consiste à imposer la condition de non-interpénétration en moyenne sur chaque élément d'un macro-maillage défini de manière idoine. Nous commençons par développer une nouvelle technique de preuve pour démontrer l'optimalité des approches de type inéquation variationnelle discrétisée par éléments finis standards pour le problème de Signorini, sans hypothèse autre que la régularité Sobolev de la solution du problème continu. Puis nous définissons la méthode LAC et démontrons, à l'aide des nouveaux outils techniques, l'optimalité de cette approche locale modélisant le contact unilatéral dans le cas général des maillages incompatibles. Pour finir, nous introduisons la formulation mixte équivalente et démontrons son optimalité et sa stabilité. Dans la seconde partie de la thèse, nous nous intéressons à l'étude numérique de la méthode LAC. Nous confirmons sa capacité à gérer numériquement le contact unilatéral avec maillages incompatibles de manière optimale à l'instar des méthodes "mortar" classiques, tout en restant facilement implémentable dans un code de calcul industriel. On montre ainsi, entre autres, que la méthode passe avec succès le patch test de Taylor. Finalement, nous montrons son apport en terme de robustesse et au niveau de la qualité des pressions de contact sur une étude de type industrielleIn this thesis, we develop a local "mortar" kind method to deal with the problem of contact with non-matching meshes in an optimal way into a finite element code of industrial level. In the first part of the thesis, we introduce the mathematical framework of the Local Average Contact method (LAC). This approach consists in satisfying the non-interpenetration condition in average on each element of a macro-mesh defined in a suitable way. We start by developing a new technique for proving the optimality of variational inequality approaches discretized by finite elements modeling Signorini problem without other hypothesis than the Sobolev regularity of the solution of the continuous problem. Then we define the LAC method and prove, using the new technical tools, the optimality of this local approach modeling the unilateral contact in the general case of non-matching meshes. Finally, we introduce the equivalent mixed formulation and prove its optimality and stability. In the second part of the thesis, we are interested in the numerical study of the LAC method. We confirm its ability to optimally treat the contact problem when considering non-matching meshes like standard "mortar" methods, while remaining easily implementable in an industrial finite element code. We show, for example, that the method successfully passes the Taylor patch test. Finally, we show its contribution in terms of robustness and at the quality of the contact pressures on an industrial study
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Sastre, Martinez Javier Miguel. "Efficient finite-state algorithms for the application of local grammars." Thesis, Paris Est, 2011. http://www.theses.fr/2011PEST1047/document.
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Notre travail porte sur le développement d'algorithmes performants d'application de grammaires locales, en prenant comme référence ceux des logiciels libres existants : l'analyseur syntaxique descendant d'Unitex et l'analyseur syntaxique à la Earley d'Outilex. Les grammaires locales sont un formalisme de représentation de la syntaxe des langues naturelles basé sur les automates finis. Les grammaires locales sont un modèle de construction de descriptions précises et à grande échelle de la syntaxe des langues naturelles par le biais de l'observation systématique et l'accumulation méthodique de données. L'adéquation des grammaires locales pour cette tâche a été testée à l'occasion de nombreux travaux. À cause de la nature ambiguë des langues naturelles et des propriétés des grammaires locales, les algorithmes classiques d'analyse syntaxique tels que LR, CYK et ne peuvent pas être utilisés dans le contexte de ce travail. Les analyseurs top-down et Earley sont des alternatives possibles ; cependant, ils ont des coûts asymptotiques exponentiels pour le cas des grammaires locales. Nous avons d'abord conçu un algorithme d'application de grammaires locales avec un coût polynomial dans le pire des cas. Ensuite, nous avons conçu des structures de donnés performantes pour la représentation d'ensembles d'éléments et de séquences. Elles ont permis d'améliorer la vitesse de notre algorithme dans le cas général. Nous avons mis en œuvre notre algorithme et ceux des systèmes Unitex et Outilex avec les mêmes outils afin de les tester dans les mêmes conditions. En outre, nous avons mis en œuvre différents versions de chaque algorithme en utilisant nos structures de données et algorithmes pour la représentation d'ensembles et ceux fournis par la Standard Template Library (STL) de GNU. Nous avons comparé les performances des différents algorithmes et de leurs variantes dans le cadre d'un projet industriel proposé par l'entreprise Telefónica I+D : augmenter la capacité de compréhension d'un agent conversationnel qui fournit des services en ligne, voire l'envoi de SMS à des téléphones portables ainsi que des jeux et d'autres contenus numériques. Les conversations avec l'agent sont en espagnol et passent par Windows Live Messenger. En dépit du domaine limité et de la simplicité des grammaires appliquées, les temps d'exécution de notre algorithme, couplé avec nos structures de données et algorithmes pour la représentation d'ensembles, ont été plus courts. Grâce au coût asymptotique amélioré, on peut s'attendre à des temps d'exécution significativement inférieurs par rapport aux algorithmes utilisés dans les systèmes Unitex et Outilex, pour le cas des grammaires complexes et à large couvertureThis work focuses on the research and development of efficient algorithms of application of local grammars, taking as reference those of the currently existent open-source systems : Unitex's top-down parser and Outilex's Earley-like parser. Local grammars are a finite-state based formalism for the representation of natural language grammars. Moreover, local grammars are a model for the construction of fully scaled and accurated descriptions of the syntax of natural languages by means of systematic observation and methodical accumulation of data. The adequacy of local grammars for this task has been proved by multiple works. Due to the ambiguous nature of natural languages, and the particular properties of local grammars, classic parsing algorithms such as LR, CYK's and Tomita's cannot be used in the context of this work. Top-down and Earley parsers are possible alternatives, though they have an exponential worst-case cost for the case of local grammars. We have first conceived an algorithm of application of local grammars having a polynomial worst-case cost. Furthermore, we have conceived other optimizations which increase the efficiency of the algorithm for general cases, namely the efficient management of sets of elements and sequences. We have implemented our algorithm and those of the Unitex and Outilex systems with the same tools in order to test them under the same conditions. Moreover, we have implemented different versions of each algorithm, either using our custom set data structures or those included in GNU's implementation of the C++ Standard Template Library (STL). We have compared the performances of the different algorithms and algorithm versions in the context of an industrial natural language application provided by the enterprise Telefónica I+D : extending the understanding capabilities of a chatterbot that provides mobile services, such as sending SMSs to mobile phones as well as games and other digital contents. Conversation with the chatterbot is held in Spanish by means of Microsoft's Windows Live Messenger. In spite of the limited domain and the simplicity of the applied grammars, execution times of our parsing algorithm coupled with our custom implementation of sets were lower. Thanks to the improved asymptotic cost of our algorithm, execution times for the case of complex and large coverage grammars can be expected to be considerably lower than those of the Unitex and Outilex algorithms
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Valivarthi, Mohan Varma, and Hema Chandra Babu Muthyala. "A Finite Element Time Relaxation Method." Thesis, Högskolan i Halmstad, Sektionen för Informationsvetenskap, Data– och Elektroteknik (IDE), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:hh:diva-17728.
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In our project we discuss a finite element time-relaxation method for high Reynolds number flows. The key idea consists of using local projections on polynomials defined on macro element of each pair of two elements sharing a face. We give the formulation for the scalar convection–diffusion equation and a numerical illustration.
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Preissig, R. Stephen. "Local p refinement in two dimensional vector finite elements." Thesis, Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/13739.
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Nolting, Josh W. "Efficiency-based local adaptive refinement for FOSLS finite elements." Connect to online resource, 2008. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3303843.
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Henderson, Darrall. "Assessing the Finite-Time Performance of Local Search Algorithms." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/26926.
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Identifying a globally optimal solution for an intractable discrete optimization problem is often cost prohibitive. Therefore, solutions that are within a predetermined threshold are often acceptable in practice. This dissertation introduces the concept of B-acceptable solutions where B is a predetermined threshold for the objective function value.
It is difficult to assess a priori the effectiveness of local search algorithms, which makes the process of choosing parameters to improve their performance difficult. This dissertation introduces the B-acceptable solution probability in terms of B-acceptable solutions as a finite-time performance measure for local search algorithms. The B-acceptable solution probability reflects how effectively an algorithm has performed to date and how effectively an algorithm can be expected to perform in the future. The B-acceptable solution probability is also used to obtain necessary asymptotic convergence (with probability one) conditions. Upper and lower bounds for the B-acceptable solution probability are presented. These expressions assume particularly simple forms when applied to specific local search strategies such as Monte Carlo search and threshold accepting. Moreover, these expressions provide guidelines on how to manage the execution of local search algorithm runs. Computational experiments are reported to estimate the probability of reaching a B-acceptable solution for a fixed number of iterations. Logistic regression is applied as a tool to estimate the probability of reaching a B-acceptable solution for values of B close to the objective function value of a globally optimal solution as well as to estimate this objective function value. Computational experiments are reported with logistic regression for pure local search, simulated annealing and threshold accepting applied to instances of the TSP with known optimal solutions.Ph. D.
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Sastre, Javier M. "Efficient finite-state algorithms for the application of local grammars." Phd thesis, Université de Marne la Vallée, 2011. http://tel.archives-ouvertes.fr/tel-00621249.
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Notre travail porte sur le développement d'algorithmes performants d'application de grammaires locales, en prenant comme référence ceux des logiciels libres existants: l'analyseur syntaxique descendant d'Unitex et l'analyseur syntaxique à la Earley d'Outilex. Les grammaires locales sont un formalisme de représentation de la syntaxe des langues naturelles basé sur les automates finis. Les grammaires locales sont un modèle de construction de descriptions précises et à grande échelle de la syntaxe des langues naturelles par le biais de l'observation systématique et l'accumulation méthodique de données. L'adéquation des grammaires locales pour cette tâche a été testée à l'occasion de nombreux travaux. À cause de la nature ambiguë des langues naturelles et des propriétés des grammaires locales, les algorithmes classiques d'analyse syntaxique tels que LR, CYK et Tomita ne peuvent pas être utilisés dans le contexte de ce travail. Les analyseurs descendant et Earley sont des alternatives possibles, cependant, ils ont des coûts asymptotiques exponentiels pour le cas des grammaires locales. Nous avons d'abord conçu un algorithme d'application de grammaires locales avec un coût polynomial dans le pire des cas. Ensuite, nous avons conçu des structures de données performantes pour la représentation d'ensembles d'éléments et de séquences. Elles ont permis d'améliorer la vitesse de notre algorithme dans le cas général. Nous avons mis en oeuvre notre algorithme et ceux des systèmes Unitex et Outilex avec les mêmes outils afin de les tester dans les mêmes conditions. En outre, nous avons mis en oeuvre différentes versions de chaque algorithme en utilisant nos structures de données et algorithmes pour la représentation d'ensembles et ceux fournis par la Standard Template Library (STL) de GNU. Nous avons comparé les performances des différents algorithmes et de leurs variantes dans le cadre d'un projet industriel proposé par l'entreprise Telefónica I+D: augmenter la capacité de compréhension d'un agent conversationnel qui fournit des services en ligne, voire l'envoi de SMS à des téléphones portables ainsi que des jeux et d'autres contenus numériques. Les conversations avec l'agent sont en espagnol et passent par Windows Live Messenger. En dépit du domaine limité et de la simplicité des grammaires appliquées, les temps d'exécution de notre algorithme, couplé avec nos structures de données et algorithmes pour la représentation d'ensembles, ont été plus courts. Grâce au coût asymptotique amélioré, on peut s'attendre à des temps d'exécution significativement inférieurs par rapport aux algorithmes utilisés dans les systèmes Unitex et Outilex, pour le cas des grammaires complexes et à large couverture.
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Hadidimoud, S. "Modelling local damage and material rupture (using finite element method)." Thesis, University of Surrey, 2000. http://epubs.surrey.ac.uk/998/.
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