Search for dissertations about: "symmetriska"

Showing result 1 - 5 of 26 swedish dissertations containing the word symmetriska.

  2. 1. On Methods for Solving Symmetric Systems of Linear Equations Arising in Optimization

    Author : Tove Odland; Anders Forsgren; William W. Hager; KTH; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; symmetric system of linear equations; method of conjugate gradients; quasi-Newton method; unconstrained optimization; unconstrained quadratic optimiza- tion; Krylov subspace method; unnormalized Lanczos vectors; minimum-residual method; symmetriska linjära ekvationssystem; konjugerade gradientmetoden; kvasi- Newtonmetoder; optimering utan bivillkor; kvadratisk optimering utan bivillkor; Kry- lovunderrumsmetoder; icke-normaliserade Lanczosvektorer; minimum-residualmetoden; Mathematics; Matematik;

    Abstract : In this thesis we present research on mathematical properties of methods for solv- ing symmetric systems of linear equations that arise in various optimization problem formulations and in methods for solving such problems.In the first and third paper (Paper A and Paper C), we consider the connection be- tween the method of conjugate gradients and quasi-Newton methods on strictly convex quadratic optimization problems or equivalently on a symmetric system of linear equa- tions with a positive definite matrix. READ MORE

  4. 2. Harmonic morphisms, Hermitian structures and symmetric spaces

    Author : Martin Svensson; Matematik (naturvetenskapliga fakulteten); []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; isotropic subbundles; conformal foliations; holomorphic maps; harmonic morphism;

    Abstract : A harmonic morphism is a map between two Riemannian manifolds with the property that its composition with a local harmonic function on the codomain is a local harmonic function on the domain. Such a map is automatically a harmonic map, satisfying an additional partial conformality condition called horizontal (weak) conformality. READ MORE

  5. 3. A numerical study of mixing phenomena and reaction front propagation in partially premixed combustion engines

    Author : Christian Ibron; Strömningsteknik; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; CFD simulation; förbränning; antändning;

    Abstract : This work treats the modelling of PPC engine combustion through 3D computational fluid dynamics. In order to develop a cost-effective CFD model for the design and performance analysis of PPC engines it is important to first understand the multiple modes of combustion in PPC engines, e.g. READ MORE

  6. 4. Strong Cosmic Censorship and Cosmic No-Hair in spacetimes with symmetries

    Author : Katharina Maria Radermacher; Hans Ringström; James Isenberg; KTH; []
    Keywords : NATURVETENSKAP; NATURAL SCIENCES; NATURVETENSKAP; NATURAL SCIENCES; Cosmic Censorship; Cosmic No-Hair; Big Bang; symmetry; Bianchi; T2-symmetry; Gowdy; general relativity; cosmology; late time; initial time; asymptotic behaviour; perfect fluid; scalar field; Einstein equations; Mathematics; Matematik;

    Abstract : This thesis consists of three articles investigating the asymptotic behaviour of cosmological spacetimes with symmetries arising in Mathematical General Relativity.In Paper A and B, we consider spacetimes with Bianchi symmetry and where the matter model is that of a perfect fluid. READ MORE

  7. 5. Reflector Optimization for Low Concentration Photovoltaic-Thermal Solar Collectors

    Author : Diogo Cabral; Hans Wigö; Björn O. Karlsson; Maria João Carvalho; Högskolan i Gävle; []
    Keywords : TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Photovoltaic-thermal collector; experimental assessment; collector performance assessment; optical efficiency; concentrating PVT solar collector; ray tracing; Fotovoltaisk-termisk kollektor; experimentell utvärdering; prestandautvärdering; optisk effektivitet; koncentrerande PVT-solfångare; strålgångsanalys;

    Abstract : The alarming new global warming and increasing awareness related to climate change (mainly due to the high emissions of carbon dioxide) in recent decades linked all nations into a common cause, which requires ambitious efforts to combat climate change by adapting energy systems to its effects.The knowledge gain presented in this dissertation establishes the foundations for the development of a more efficient concentrating photovoltaic-thermal (PVT) solar collector. READ MORE