Sökning: "Non-linear spectral problem"

Visar resultat 1 - 5 av 13 avhandlingar innehållade orden Non-linear spectral problem.

1. 1. Non-selfadjoint operator functions

   Författare :Axel Torshage; Christian Engström; Marco Marletta; Umeå universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Non-linear spectral problem; numerical range; pseudospectrum; resolvent estimate; equivalence after extension; block operator matrices; operator functions; operator pencil; spectral divisor; joint numerical range; Mathematics; matematik;

   Sammanfattning : Spectral properties of linear operators and operator functions can be used to analyze models in nature. When dispersion and damping are taken into account, the dependence of the spectral parameter is in general non-linear and the operators are not selfadjoint. LÄS MER

3. 2. Group-Sparse Regression : With Applications in Spectral Analysis and Audio Signal Processing

   Författare :Ted Kronvall; Statistical Signal Processing Group; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; sparse regression; group-sparsity; statistical modeling; regularization; hyperparameter-selection; spectral analysis; audio signal processing; classification; localization; multi-pitch estimation; chroma; convex optimization; ADMM; cyclic coordinate descent; proximal gradient;

   Sammanfattning : This doctorate thesis focuses on sparse regression, a statistical modeling tool for selecting valuable predictors in underdetermined linear models. By imposing different constraints on the structure of the variable vector in the regression problem, one obtains estimates which have sparse supports, i.e. LÄS MER

4. 3. Asymptotic analysis of solutions to elliptic and parabolic problems

   Författare :Peter Rand; Vladimir Kozlov; Mikael Langer; Vitali Liskevich; Linköpings universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Asymptotic behaviour; The Emden-Fowler equation; Parabolic system; Spectral splitting; Cylinder; Perturbation; MATHEMATICS; MATEMATIK;

   Sammanfattning : In the thesis we consider two types of problems. In Paper 1, we studysmall solutions to a time-independent nonlinear elliptic partial differential equation of Emden-Fowler type in a semi-infnite cylinder. The asymptotic behaviour of these solutions at infnity is determined. First, the equation under the Neumann boundary condition is studied. LÄS MER

5. 4. Estimation and Classification of Non-Stationary Processes : Applications in Time-Frequency Analysis

   Författare :Johan Brynolfsson; Statistical Signal Processing Group; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Time-Frequency Estimation; Parameter Estimation; Reassignment method; Non-Stationary Processes; Smooth spectral estimation; Neural Networks;

   Sammanfattning : This thesis deals with estimation and classification problems of non-stationary processes in a few special cases.In paper A and paper D we make strong assumptions about the observed signal, where a specific model is assumed and the parameters of the model are estimated. LÄS MER

7. 5. Studies of vector tomography

   Författare :Kent Stråhlén; Matematik LTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Doppler tomography; Doppler Radon transform; local tomography; vectorial k-plane transform; vectorial Radon transform; k-plane transform; Radon transform; tomography; vector tomography; Mathematics; Matematik;

   Sammanfattning : The motivation to study the kind of problems appearing in this thesis has been ultrasound measurements of flows, from which velocity spectra along lines can be determined. These velocity spectra can mathematically be described by a new non-linear transform, here called the Doppler Spectral Transform (DST). LÄS MER