Institutt for matematikk og statistikk

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Institutt for matematikk og statistikk

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• Artikler, rapporter og annet (matematikk og statistikk) [51]
• Mastergradsoppgaver i matematikk [8]
• Mastergradsoppgaver i statistikk [3]
• Mastergradsoppgaver i teknologi - industriell matematikk [4]

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• 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)

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  Abstract:

  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 seed regions, likely to correspond to samples of skin and the lesion of interest. The seed regions are used as initial training samples, and the lesion segmentation problem is treated as binary classification problem. An iterative hybrid classification strategy, based on a weighted combination of estimated posteriors of a linear and quadratic classifier, is used to update both the automatically selected training samples and the segmentation, increasing reliability and final accuracy, especially for those challenging images, where the contrast between the background skin and lesion is low.

  URI:

  http://hdl.handle.net/10037/3975

  File(s) in this item: 1

  article.pdf   (6.131Mb)
• 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)

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  Abstract:

  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. 800-1800) is characterized by a progressive winter cooling of approximately 0.9°C century-1 (0.3°C century-1 for Vardø) and a lack of distinct signs of abrupt climate transitions. This makes it difficult to associate the onset of the Little Ice Age in Svalbard with any particular time period. During the 1800s, which according to our results was the coldest century in Svalbard, the winter cooling associated with the Little Ice Age was on the order of 4°C (1.3°C for Vardø) compared to the 1900s. The rapid warming that commenced at the beginning of the 20th century was accompanied by a parallel decline in sea-ice extent in the study area. However, both the reconstructed winter temperatures as well as indirect indicators of summer temperatures suggest the Medieval period before the 1200s was at least as warm as at the end of the 1990s in Svalbard.

  URI:

  http://hdl.handle.net/10037/3945

  File(s) in this item: 1

  article.pdf   (867.5Kb)
• Scale Space Methods for Analysis of Type 2 Diabetes Patients' Blood Glucose Values

  Skrøvseth, Stein Olav; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2011)

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  Abstract:

  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 in reliability of the recordings. Scale space andfrequency space techniques are suited to reveal important features of unevenly sampled data, and useful for identifying medically relevant features for use both by patients as part of theirself-management process, and provide useful information for physicians.

  URI:

  http://hdl.handle.net/10037/3940

  File(s) in this item: 1

  article.pdf   (1.350Mb)
• Matematisk kulturhistorie : artikkelsamling

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

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  URI:	http://hdl.handle.net/10037/3247

  File(s) in this item: 1

  book.pdf   (6.259Mb)
• A stochastic theory for temporal fluctuations in self-organized critical systems

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

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  URI:	http://hdl.handle.net/10037/3144

  File(s) in this item: 1

  article.pdf   (840.9Kb)

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