Viser treff 251-270 av 314

    • 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 ...
    • Scaling of global temperatures explained by linear energy balance models 

      Rypdal, Kristoffer; Fredriksen, Hege-Beate (Journal article; Tidsskriftartikkel; Peer reviewed, 2017-12)
      <i>Introduction</i>: Scale invariance of natural variability of global surface temperatures is often interpreted as a signature of nonlinear dynamics. However, the observed scaling can be adequately explained by linear energy balance involving subsystems with different response times.
    • SDiff(2) and uniqueness of the Plebanski equation 

      Kruglikov, Boris; Morozov, Oleg (Journal article; Tidsskriftartikkel; Peer reviewed, 2012)
      The group of area preserving diffeomorphisms showed importance in the problems of self-dual gravity and integrability theory. We discuss how representations of this infinite-dimensional Lie group can arise in mathematical physics from pure local considerations. Then using Lie algebra extensions and cohomology we derive the second Plebański equation and its geometry. We do not use Kähler or other ...
    • Seafood production in Northern Norway: Analyzing variation and co-development in aquaculture and coastal fisheries 

      Espinasse, Marina; Mikkelsen, Eirik Inge; Sørbye, Sigrunn Holbek; Skern-Mauritzen, Mette; Falk-Andersson, Jannike; Fauchald, Per (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-07-27)
      Norway is one of the leading ocean-based food production nations. Its seafood industry comprises wild-capture fisheries and farmed fish production. Both industries play a provisional role but also contribute to economic development of the country and help sustain coastal communities, particularly, in Northern Norway. Coastal fishery has been the staple industry in Northern Norway for centuries, while ...
    • Seasonality, density dependence, and spatial population synchrony 

      Antunes Lopes Da Silva Nicolau, Pedro Guilherme; Ims, Rolf Anker; Sørbye, Sigrunn Holbek; Yoccoz, Nigel (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12-15)
      Studies of spatial population synchrony constitute a central approach for understanding the drivers of ecological dynamics. Recently, identifying the ecological impacts of climate change has emerged as a new important focus in population synchrony studies. However, while it is well known that climatic seasonality and sequential density dependence influences local population dynamics, the role of ...
    • Second-Order PDEs in 3D with Einstein–Weyl Conformal Structure 

      Berjawi, S.; Ferapontov, E.V.; Kruglikov, Boris; Novikov, V.S. (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-12-07)
      Einstein–Weyl geometry is a triple (D,g,ω) where D is a symmetric connection, [g] is a conformal structure and ω is a covector such that ∙ connection D preserves the conformal class [g], that is, Dg=ωg; ∙ trace-free part of the symmetrised Ricci tensor of D vanishes. Three-dimensional Einstein–Weyl structures naturally arise on solutions of second-order dispersionless integrable PDEs in 3D. In this ...
    • Second-order PDEs in four dimensions with half-flat conformal structure 

      Berjawi, S.; Ferapontov, Eugene V.; Kruglikov, Boris; Novikov, Vladimir S (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-01-29)
      We study second-order partial differential equations (PDEs) in four dimensions for which the conformal structure defined by the characteristic variety of the equation is half-flat (self-dual or anti-self-dual) on every solution. We prove that this requirement implies the Monge–Ampère property. Since half-flatness of the conformal structure is equivalent to the existence of a non-trivial dispersionless ...
    • Self-assessment of written exercises in STEM courses 

      Irgens, Børge; Coucheron, David Andre (Conference object; Konferansebidrag, 2023-03)
      Students of physics in Norway typically spend a lot of time on mandatory problemsolving exercises that they must get a passing grade on to be allowed to take the exam. This is often a primarily summative assessment, which can limit the learning potential. <p> <p>In this contribution, we present an intervention in which traditional mandatory assignments are modified to put more emphasis on ...
    • A semiautomatic tool for prostate segmentation in radiotherapy treatment planning 

      Schulz, Jörn; Skrøvseth, Stein Olav; Tømmerås, Veronika Kristine; Marienhagen, Kirsten; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2014-01-25)
    • Shellability and homology of q-complexes and q-matroids 

      Ghorpade, Sudhir R.; Pratihar, Rakhi; Randrianarisoa, Tovohery H. (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-07-09)
      We consider a q-analogue of abstract simplicial complexes, called q-complexes, and discuss the notion of shellability for such complexes. It is shown that q-complexes formed by independent subspaces of a q-matroid are shellable. Further, we explicitly determine the homology of q-complexes corresponding to uniform q-matroids. We also outline some partial results concerning the determination of homology ...
    • A simple criterion for the m-cyclicity of the group of rational points on an elliptic curve defined over a finite field 

      Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2006-02)
      We give a simple criterion for the cyclicity of the m-torsion subgroup of the group of rational points on an elliptic curve defined over a finite field of characteristic larger than 3 for m = 2, 3, 4, 6, 12.
    • Simplifying Clustering with Graph Neural Networks 

      Bianchi, Filippo Maria (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-01-23)
      The objective functions used in spectral clustering are generally composed of two terms: i) a term that minimizes the local quadratic variation of the cluster assignments on the graph and; ii) a term that balances the clustering partition and helps avoiding degenerate solutions. This paper shows that a graph neural network, equipped with suitable message passing layers, can generate good cluster ...
    • Snow avalanche segmentation in SAR images with Fully Convolutional Neural Networks 

      Bianchi, Filippo Maria; Grahn, Jakob; Eckerstorfer, Markus; Malnes, Eirik; Vickers, Hannah (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-10)
      Knowledge about frequency and location of snow avalanche activity is essential for forecasting and mapping of snow avalanche hazard. Traditional field monitoring of avalanche activity has limitations, especially when surveying large and remote areas. In recent years, avalanche detection in Sentinel-1 radar satellite imagery has been developed to improve monitoring. However, the current state-of-the-art ...
    • The South American monsoon approaches a critical transition in response to deforestation 

      Bochow, Nils; Boers, Niklas (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-04)
      The Amazon rainforest is threatened by land-use change and increasing drought and fire frequency. Studies suggest an abrupt dieback of large parts of the rainforest after partial forest loss, but the critical threshold, underlying mechanisms, and possible impacts of forest degradation on the monsoon circulation remain uncertain. Here, we use a nonlinear dynamical model of the moisture transport ...
    • Spatial trend analysis of gridded temperature data at varying spatial scales 

      Haug, Ola; Thorarinsdottir, Thordis Linda; Sørbye, Sigrunn Holbek; Franzke, Christian L.E. (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-02-28)
      Classical assessments of trends in gridded temperature data perform independent evaluations across the grid, thus, ignoring spatial correlations in the trend estimates. In particular, this affects assessments of trend significance as evaluation of the collective significance of individual tests is commonly neglected. In this article we build a space–time hierarchical Bayesian model for temperature ...
    • Spatio-temporal variability of Arctic summer temperatures over the past 2 millennia 

      Werner, Johannes; Divine, Dmitry V; Ljungqvist, Fredrik Charpentier; Nilsen, Tine; Francus, Pierre (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-24)
      <p>In this article, the first spatially resolved and millennium-length summer (June–August) temperature reconstruction over the Arctic and sub-Arctic domain (north of 60°N) is presented. It is based on a set of 44 annually dated temperature-sensitive proxy archives of various types from the revised PAGES2k database supplemented with six new recently updated proxy records. As a major advance, an ...
    • Spatiotemporal Analysis of COVID-19 Incidence Data 

      Spassiani, Ilaria; Sebastiani, Giovanni; Palu, Giorgio (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-03-11)
      High-density lipoproteins (HDL) are a heterogenous group of plasma molecules with a large variety in composition. There is a wide specter in lipid content and the number of different proteins that has been associated with HDL is approaching 100. Given this heterogeneity and the fact that the total amount of HDL is inversely related to the risk of coronary heart disease (CHD), there has been ...
    • Spatiotemporal Long-Range Persistence in Earth’s Temperature Field: Analysis of Stochastic-Diffusive Energy Balance Models 

      Rypdal, Kristoffer; Rypdal, Martin Wibe; Fredriksen, Hege-Beate (Journal article; Tidsskriftartikkel; Peer reviewed, 2015-11-01)
      A two-dimensional stochastic–diffusive energy balance model (EBM) formulated on a sphere by G. R. North et al. is explored and generalized. Instantaneous and frequency-dependent spatial autocorrelation functions and local temporal power spectral densities are computed for local sites and for spatially averaged surface temperature signals up to the global scale. On time scales up to the relaxation ...
    • Spectral characteristics of instrumental and climate model surface temperatures 

      Fredriksen, Hege-Beate; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2016-02-05)
      The spatiotemporal temperature variability for several gridded instrumental and general circulation climate model data is characterized, contrasting power spectra of local and global temperatures, land and sea temperatures, and temperatures of different regions. There is generally a high degree of agreement between the spectral characteristics of instrumental and climate model data. All but the ...
    • Spectral clustering with graph neural networks for graph pooling 

      Bianchi, Filippo Maria; Grattarola, Daniele; Alippi, Cesare (Conference object; Konferansebidrag, 2020)
      Spectral clustering (SC) is a popular clustering technique to find strongly connected communities on a graph. SC can be used in Graph Neural Networks (GNNs) to implement pooling operations that aggregate nodes belonging to the same cluster. However, the eigendecomposition of the Laplacian is expensive and, since clustering results are graph-specific, pooling methods based on SC must perform a ...