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04906 Discrete Ill-Posed Problems
Danish title: Discrete Ill-Posed Problems
Language: English Credit points: 5,1
Type: Ph.D.-level, Open University
Language: English

Compulsory: basic knowledge of numerical analysis
Recommended semester: 7th - 9th semester
Scope and form: lectures and exercises
Examination: Evaluation of report(s) (Pass/fail)
Contact person: Per Christian Hansen, Building 305, Tel. +45 4525 3097, email pch@imm.dtu.dk, http://www.imm.dtu.dk/~pch

Department: Informatics and Mathematical Modelling
Aim: The course describes the numerical treatment of inverse problems, with emphasis on various algorithms for computing stabilized solutions via incorporation of a priori information. The characteristics of inverse problems are discussed with emphasis on those aspects that influence their numerical splution. The inversion algorithms are described and compared in a commen framework, and their stable and efficient numerical implementation is discussed. The theory is illustrated with examples from e.g. seismology and signal processing.
Contents: Introduction to inverese problems Discretization methods. Numerical linear algebra for discrete inverse problems; QR-factorization, singular value decomposition (SVD), and conjugate gradients (CG). Analysis of discrete ill-posed problems by means of the L-curve. Direct and iterative regularization methosd. Choice of smoothing norm and regularization parameter. Computer exercises using Matlab and the regularization tools toolbox Course plan: Day 1: Introduction, Singular value expansion. Day 2: Rank-dificient problems, SVD, GSVD. Day 3: Tikhonov regularization, Standard-form reduction. Day 4: Picard condition, L-curve analysis. Day 5: Seminorms, The TSVD family, Mollifier methods. Day 6: Parameter - choice methods. Day 7: Iterative methods.