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norskInstitutt for matematikk og statistikk: Recent submissions
Now showing items 361-380 of 437
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A toolbox for fitting complex spatial point process models using integrated nested Laplace approximation (INLA)
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)This paper develops methodology that provides a toolbox for routinely fitting complex models to realistic spatial point pattern data. We consider models that are based on log-Gaussian Cox processes and include local interaction in these by considering constructed covariates. This enables us to use integrated nested Laplace approximation and to considerably speed up the inferential task. In addition, ... -
On hybrid classification using model assisted posterior estimates
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)Traditional parametric and nonparametric classifiers used for statistical pattern recognition have their own strengths and limitations. While parametric methods assume some specific parametric models for density functions or posterior probabilities of competing classes, nonparametric methods are free from such assumptions. So, when these model assumptions are correct, parametric methods outperform ... -
Wei-type duality theorems for matroids
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)We present several fundamental duality theorems for matroids and more general combinatorial structures. As a special case, these results show that the maximal cardinalities of fixed-ranked sets of a matroid determine the corresponding maximal cardinalities of the dual matroid. Our main results are applied to perfect matroid designs, graphs, transversals, and linear codes over division rings, in each ... -
Bayesian multiscale analysis of images modeled as Gaussian Markov random fields
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)A Bayesian multiscale technique for the detection of statistically significant features in noisy images is proposed. The prior is defined as a stationary intrinsic Gaussian Markov random field on a toroidal graph, which enables efficient computation of the relevant posterior marginals. Hence the method is applicable to large images produced by modern digital cameras. The technique is demonstrated ... -
Multicentennial Variability of the Sea Surface Temperature Gradient across the Subpolar North Atlantic over the Last 2.8 kyr
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)A 2800-yr-long August sea surface temperature (aSST) record based on fossil diatom assemblages is generated from a marine sediment core from the northern subpolar North Atlantic. The record is compared with the aSST record from the Norwegian Sea to explore the variability of the aSST gradient between these areas during the late Holocene. The aSST records demonstrate the opposite climate tendencies ... -
Automatic nematode detection in cod fillets (Gadus morhua L.) by hyperspectral imaging
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)Detection of objects embedded in tissue, using visible light, is difficult due to light scattering. The optical properties of the surrounding tissue will influence the spectral characteristics of the light interacting with the object, and the spectral signature observed from the object will be directly affected. A method for calibrating the spectral signature of small objects, embedded in translucent ... -
Pairwise scale space comparison of time series with application to climate research
(Journal article; Tidsskriftartikkel; Peer reviewed, 2012)In this paper, we study how sea surface temperature variations in the North Atlantic and the Norwegian Sea are correlated with the climate in the Northern Hemisphere in late Holocene. The analysis is performed by testing statistical hypotheses through novel scale space methodologies. In late Holocene, the proposed techniques reveal that the climate development in the subpolar North Atlantic has been ... -
Numerical calculation of Casimir forces
(Master thesis; Mastergradsoppgave, 2012-06-19)In this thesis a set of regularized boundary integral equation are introduced that can be used to calculate the Casimir force induced by a two dimensional scalar field. The boundary integral method is compared to the functional integral method and mode summation where possible. Comparisons are done for the case of two parallel plates, two concentric circles and two adjacent circles. The results ... -
Local classification of 2-dimensional solvable Lie algebra actions on the plane.
(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
(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
(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
(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
(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
(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
(Book; Bok, 2002-08) -
A stochastic theory for temporal fluctuations in self-organized critical systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2008) -
Finite Larmor radius influence on MHD solitary waves
(Journal article; Tidsskriftartikkel; Peer reviewed, 2009) -
Vanishing of the entropy pseudonorm for certain integrable systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2006) -
A propagation-separation approach to estimate the autocorrelation in a time-series
(Journal article; Tidsskriftartikkel; Peer reviewed, 2008) -
Bayesian modeling and significant features exploration in wavelet power spectra
(Journal article; Tidsskriftartikkel; Peer reviewed, 2007)
