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Visar resultat 1 - 5 av 46 avhandlingar som matchar ovanstående sökkriterier.

1. 1. Invariants of knot diagrams and diagrammatic knot invariants

   Författare :Olof-Petter Östlund; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematics; Knot theory; knot diagram; plane curve; Reidemeister move; finite degree invariant; combinatorial knot invariant; Gauss diagram; MATEMATIK; MATHEMATICS; MATEMATIK; matematik; Mathematics;

   Sammanfattning : Two knot diagrams describe isotopic knots if and only if they can be connected by a sequence of planar isotopies and Reidemeister moves (cusp-, self-tangency-, and triple point moves). In this dissertation classes of knot diagrams, Reidemeister moves, and relations between sequences of Reidemeister moves are investigated, in a manner inspired by V. LÄS MER

3. 2. Digital lines, Sturmian words, and continued fractions

   Författare :Hanna Uscka-Wehlou; Christer Oscar Kiselman; Maciej Klimek; Gunilla Borgefors; Mikael Passare; Damien Jamet; Uppsala universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; digital geometry; digital line; hierarchy of runs; combinatorics on words; Sturmian word; upper mechanical word; characteristic word; irrational slope; continued fraction; Gauss map; fixed point; Discrete mathematics; Diskret matematik; matematik; Mathematics;

   Sammanfattning : In this thesis we present and solve selected problems arising from digital geometry and combinatorics on words. We consider digital straight lines and, equivalently, upper mechanical words with positive irrational slopes a... LÄS MER

4. 3. Additively and multiplicatively structured sets

   Författare :Dmitrii Zhelezov; Göteborgs universitet; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Product set; arithmetic progression; multiplication theorem; sumset; additive energy; multiplicative energy; sum-product phenomenon; multiplicative subgroups; Gauss sums; sum-product phenomenon;

   Sammanfattning : .... LÄS MER

5. 4. Inverse Problems in Tomography and Fast Methods for Singular Convolutions

   Författare :Fredrik Andersson; Matematik LTH; []
   Nyckelord :NATURVETENSKAP; NATURAL SCIENCES; Mathematics; Matematik; Unequally spaced FFT; Integral transforms; Singular integrals; Lippmann?Schwinger equation; Helmholtz equation; Inverse problems; Fast Gauss transform; Fast summation; Convolution; Radon transform; Tomography;

   Sammanfattning : There are two, partially interlaced, themes treated in this thesis; inverse problems of tomographic type and fast and accurate methods for the application of convolution operators. Regarding the first theme, the inverse problem of Doppler tomography is considered and the Doppler moment transform is introduced for that purpose. LÄS MER

7. 5. Quantization and Noise-Shaped Coding for High Efficiency Transmitter Architectures

   Författare :Ulf Gustavsson; Chalmers tekniska högskola; []
   Nyckelord :TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; TEKNIK OCH TEKNOLOGIER; ENGINEERING AND TECHNOLOGY; Software Defined Radio; Quantization; damped Gauss-Newton; Pulse Density Modulation; Noise-Shaped Coding; ΣΔ-Modulators; Power Amplifier;

   Sammanfattning : Three driving parameters in the development of transmitter technologies for wireless communication today is: energy efficiency, flexibility and footprint reduction. This thesis investigates the use of 1-bit oversampled signal representation, mainly as a power efficiency enhancement technique for the transmitter, but also as a path toward reduced footprint and increased flexibility. LÄS MER