Sökning: "Eigenvalue"

Visar resultat 11 - 15 av 72 uppsatser innehållade ordet Eigenvalue.

  1. 11. Accelerated Density Matrix Iterations Using Eigenvalue Gaps

    Master-uppsats, Uppsala universitet/Institutionen för informationsteknologi

    Författare :Omar Ghulam Ahmed Malik; [2022]
    Nyckelord :;

    Sammanfattning : Density and Fock matrices play a significant role in electronic structure calculations, and there exist several methods to compute the density matrix from a given Fock matrix. One such method isdensity matrix purification, in which the eigenspectrum of the Fock matrix is scaled into the [0,1]interval and the Fock matrix is afterwards iterated with a sequence of polynomials that push theeigenvalues towards 1 and 0. LÄS MER

  3. 12. Computationally Efficient Methods in Topology Optimization

    Uppsats för yrkesexamina på avancerad nivå, Lunds universitet/Hållfasthetslära; Lunds universitet/Institutionen för byggvetenskaper

    Författare :Vilmer Dahlberg; [2022]
    Nyckelord :Topology Optimization; Eigenfrequency; Eigenmode; Reduced Order Model; Sensitivity Analysis; Deflation; Technology and Engineering;

    Sammanfattning : In topology optimization, iterative, gradient-based methods are used to find the material distribution of structures which maximizes some objective function, typically the structures' stiffness, or in some cases the fundamental frequency. Finite element analysis is used to compute the structural response in each iteration, leading to large systems of equations. LÄS MER

  4. 13. Embedded eigenvalues for asymptotically periodic ODE Systems

    Master-uppsats, Lunds universitet/Matematik LTH

    Författare :Wilhelm Treschow; [2022]
    Nyckelord :embedded eigenvalue perturbation theory ODE theory; Mathematics and Statistics;

    Sammanfattning : In this thesis we investigate the persistance of embedded eigenvalues under perturbations of a certain self-adjoint Schrödinger-type differential operator in L^2(\mathbb{R},\mathbb{R}^n), with an asymptotically periodic potential. The studied perturbations are small and belong to a certain Banach space with a specified decay rate, in particular, a weighted space of continuous matrix valued functions. LÄS MER

  5. 14. Phase Diagrams of Finite Spin Chains with Coupled Spin and Lattice Vibrations

    Kandidat-uppsats, Uppsala universitet/Materialteori

    Författare :Siri Alva Berge; [2021]
    Nyckelord :spin-lattice coupling; spin-vibration coupling; Heisenberg exchange; magnetism;

    Sammanfattning : The spin-lattice coupling is due to itinerant electrons interacting with both spins of ions and phonons, mediating a coupling between magnetic spin moments and lattice vibrations. In this project, the coupling is studied systematically for finite quantum spin chains of size 2 – 10. LÄS MER

  7. 15. Modeling The Temperature of a Calorimeter at Clab : Considering a Thermodynamic Model of The Temperature Evolution of The Calorimeter System 251

    Uppsats för yrkesexamina på avancerad nivå, Uppsala universitet/Tillämpad kärnfysik

    Författare :Johannes Ekman; [2021]
    Nyckelord :calorimetry; calorimeter; System 251; temperature evolution; spent nuclear fuel; SNF; MATLAB; SERPENT2; Clab; nuclear decay heat; calibration measurements; thermodynamic model; gamma escape fraction; mass correction; calibration measurements; electric heater; three component system; system of ordinary differential equations; eigenvalues; eigenvalue estimation; temperature increase method; polynomial approximation of mass correction; sensitivity of mass correction; calorimeter heat capacity; mass correction uncertainty; calorimeter calibration curve; monoenergetic gamma spectrum; curve fitting of temperature as function of time;

    Sammanfattning : It is important to know the heat generated due to nuclear decay in the final repository for spent nuclear fuel. In Sweden, the heating powers generated in spent nuclear fuels are currently measured in the calorimeter System 251 at the Clab facility, Oskarshamn. LÄS MER