Institutt for matematikk og statistikk: Nye registreringer

Viser treff 321-340 av 389

    • Local classification of 2-dimensional solvable Lie algebra actions on the plane. 

      Gustad, Christian O'cadiz (Master thesis; Mastergradsoppgave, 2010-05)
      In the thesis the local classification of 2-dimensional solvable Lie algebra action on the plane is given. Normal forms of such actions are found. The classification applied to classifcation of 2nd order differential equations that are solvable in quadratures.

    • A threshold cointegration analysis of Norwegian interest rates 

      Larsen, Berner (Master thesis; Mastergradsoppgave, 2012-04)
      In this thesis we generalize the Hansen and Seo test in the R package tsDyn, which tests a linear cointegration model against a two-regime threshold cointegration model, to the case of three regimes in the alternative hypothesis. As the Lagrange Multiplier test statistic used in the Hansen and Seo test in tsDyn is different from the LM statistic described in Hansen and Seo (2002), we generalize ...

    • Almost complex homogeneous spaces with semi-simple isotropy 

      Winther, Henrik (Master thesis; Mastergradsoppgave, 2012-05)
      We classify the almost complex structures on homogeneous spaces M = G/H of real dimension less than or equal to 6 with semi-simple isotropy group H.

    • Automatic Segmentation of Dermoscopic Images by Iterative Classification 

      Zortea, Maciel; Skrøvseth, Stein Olav; Schopf, Thomas Roger Griesbeck; Kirchesch, Herbert M.; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Accurate detection of the borders of skin lesions is a vital first step for computer aided diagnostic systems. This paper presents a novel automatic approach to segmentation of skin lesions that is particularly suitable for analysis of dermoscopic images. Assumptions about the image acquisition, in particular, the approximate location and color, are used to derive an automatic rule to select small ...

    • Thousand years of winter surface air temperature variations in Svalbard and northern Norway reconstructed from ice-core data 

      Divine, Dmitry V; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      Two isotopic ice core records from western Svalbard are calibrated to reconstruct more than 1000 years of past winter surface air temperature variations in Longyearbyen, Svalbard, and Vardø, northern Norway. Analysis of the derived reconstructions suggests that the climate evolution of the last millennium in these study areas comprises three major sub-periods. The cooling stage in Svalbard (ca. ...

    • Scale Space Methods for Analysis of Type 2 Diabetes Patients' Blood Glucose Values 

      Skrøvseth, Stein Olav; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)
      We describe how scale space methods can be used for quantitative analysis of blood glucose concentrations from type 2 diabetes patients. Blood glucose values were recorded voluntarily by the patients over one full year as part of a self-management process, where the timeand frequency of the recordings are decided by the patients. This makes a unique datasetin its extent, though with a large variation ...

    • Matematisk kulturhistorie : artikkelsamling 

      Thorvaldsen, Steinar (Book; Bok, 2002-08)

    • A stochastic theory for temporal fluctuations in self-organized critical systems 

      Rypdal, Martin; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)

    • Finite Larmor radius influence on MHD solitary waves 

      Mjølhus, Einar (Journal article; Tidsskriftartikkel; Peer reviewed, 2009)

    • Vanishing of the entropy pseudonorm for certain integrable systems 

      Kruglikov, Boris Serafimovich; Matveev, VS (Journal article; Tidsskriftartikkel; Peer reviewed, 2006)

    • A propagation-separation approach to estimate the autocorrelation in a time-series 

      Divine, Dmitry V; Polzehl, J; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2008)

    • Bayesian modeling and significant features exploration in wavelet power spectra 

      Divine, Dmitry V; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2007)

    • DeltaProt : a software toolbox for comparative genomics 

      Thorvaldsen, Steinar; Flå, Tor; Willassen, Nils P (Journal article; Tidsskriftartikkel; Peer reviewed, 2010)

    • Matroids, demi-matroids and chains of linear codes 

      Martin, James Aloysius (Master thesis; Mastergradsoppgave, 2010-12-09)
      The central theme of this thesis is the study of matroids and related concepts such as linear codes and graphs. Demi-matroids, structures which arise from a relaxation of the definition of a matroid are explored along with related themes. Finally we examine the fact that some results in coding theory are essentially consequences of results for demi-matroids.

    • Empirisk analyse og stokastisk modellering av temporale fluktuasjoner i den norske pengemarkedsrenta 

      Løvsletten, Ola (Master thesis; Mastergradsoppgave, 2010-06-01)
      I denne oppgaven analyserer vi den norske pengemarkedsrenta NIBOR (3 mnd). Vi fokuserer spesielt p\aa\ modeller som beskriver den karakteristiske potenslovskaleringen vi ser i data. Eksempler p\aa\ slike modeller er stabile L\'{e}vy-prosesser, trunkerte stabile L\'{e}vy-prosesser og multifraktale prosesser. Vi finner at modellen Markov Switching Multifractal gjenskaper de viktigste strukturelle ...

    • Extensions of groups and modules 

      Nermo, Catalina Nicole Vintilescu (Master thesis; Mastergradsoppgave, 2010)
      The main goal of this thesis is to build up detailed constructions and give complete proofs for the extension functors of modules and groups, which we define using cohomology functors. Further, we look at the relations that appear between these and short exact sequences of modules, respectively groups. We calculate also several concrete cohomology groups, and build extensions that are described by ...

    • Multi-fractal stochastic modeling of the auroral electrojet index 

      Sund, Martin Jong Yul Shon (Master thesis; Mastergradsoppgave, 2009-12-15)
      In this thesis we have analyzed the Auroral Electrojet (AE) Index over the years 2000 to 2005, a time series consisting of over 3 000 000 data points. The aim is to describe this data as a multi-fractal stochastic process. We first introduce a class of random multiplicative measures, which provide the multi-fractality in the stochastic processes that will be defined later. We also review the ...

    • Kompleksiteten til noen kryptologisk viktige algoritmer 

      Brattli, Tore (Master thesis; Mastergradsoppgave, 1990-04-04)
      Denne hovedfagsoppgaven har som mål å sammenligne teoretisk og praktisk kompleksitet til algoritmer som har stor kryptologisk betydning. Et av målene er å avsløre den skjulte konstanten bak O-notasjonen, slik at algoritmene kan sammenlignes på et reelt grunnlag. I tillegg er det sett på sammenheng mellom sikkerhet, størrelsen på tall, asymptotisk og praktisk kompleksitet. Spesielt algoritmer som ...

    • Nijenhuis tensors in pseudoholomorphic curves neighborhoods 

      Kruglikov, Boris (Working paper; Arbeidsnotat, 2000)
      In this paper we consider the normal forms of almost complex structures in a neighborhood of pseudoholomorphic curve. We define normal bundles of such curves and study the properties of linear bundle almost complex structures. We describe 1-jet of the almost complex structure along a curve in terms of its Nijenhuis tensor. For pseudoholomorphic tori we investigate the problem of pseudoholomorphic ...

    • Symmetry approaches for reductions of PDEs, differential constraints and Lagrange-Charpit method 

      Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2007-12-20)
      Many methods for reducing and simplifying differential equations are known. They provide various generalizations of the original symmetry approach of Sophus Lie. Plenty of relations between them have been noticed and in this note a unifying approach will be discussed. It is rather close to the differential constraint method, but we make this rigorous basing on recent advances in compatibility ...