Blar i Bergen Open Research Archive på forfatter "Nævdal, Geir"
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Bridging the ensemble Kalman filter and particle filters: the adaptive Gaussian mixture filter
Stordal, Andreas Størksen; Karlsen, Hans A.; Nævdal, Geir; Skaug, Hans J.; Vallès, Brice (Peer reviewed; Journal article, 2010)The nonlinear filtering problem occurs in many scientific areas. Sequential Monte Carlo solutions with the correct asymptotic behavior such as particle filters exist, but they are computationally too expensive when working ... -
Fluid-sensitive migration mechanisms predict association between metastasis and high interstitial fluid pressure in pancreatic cancer
Nævdal, Geir; Rofstad, Einar K; Søreide, Kjetil; Evje, Steinar (Journal article; Peer reviewed, 2022)A remarkable feature in pancreatic cancer is the propensity to metastasize early, even for small, early stage cancers. We use a computer-based pancreatic model to simulate tumor progression behavior where fluid-sensitive ... -
Homotopy method for seismic modeling in strongly scattering acoustic media with density variation
Xiang, Kui; Jakobsen, Morten; Eikrem, Kjersti Solberg; Nævdal, Geir (Journal article; Peer reviewed, 2020)The wave equation for acoustic media with variable density and velocity can be transformed into an integral equation of the Lippmann-Schwinger type; but for a 4-dimensional state vector involving the gradient of the pressure ... -
Homotopy scattering series for seismic forward modelling with variable density and velocity
Xiang, Kui; Eikrem, Kjersti Solberg; Jakobsen, Morten; Nævdal, Geir (Journal article; Peer reviewed, 2021)We have derived a convergent scattering series solution for the frequency-domain wave equation in acoustic media with variable density and velocity. The convergent scattering series solution is based on the homotopy analysis ... -
Mathematics and Medicine: How mathematics, modelling and simulations can lead to better diagnosis and treatments
Hanson, Erik Andreas; Hodneland, Erlend; Lorentzen, Rolf Johan; Nævdal, Geir; Nordbotten, Jan Martin; Sævareid, Ove; Zanna, Antonella (Lecture Notes in Computational Science and Engineering, Chapter; Peer reviewed; Journal article, 2019)Starting with the discovery of X-rays by Röntgen in 1895, the progress in medical imaging has been extraordinary and immensely beneficial to diagnosis and therapy. Parallel to the increase of imaging accuracy, there is the ... -
A new framework for assessing subject-specific whole brain circulation and perfusion using MRI-based measurements and a multi-scale continuous flow model
Hodneland, Erlend; Hanson, Erik Andreas; Sævareid, Ove; Nævdal, Geir; Lundervold, Arvid; Solteszova, Veronika; Zanna, Antonella; Deistung, Andreas; Reichenbach, Jürgen; Nordbotten, Jan Martin (Peer reviewed; Journal article, 2019-06-25)A large variety of severe medical conditions involve alterations in microvascular circulation. Hence, measurements or simulation of circulation and perfusion has considerable clinical value and can be used for diagnostics, ... -
Sampling error distribution for the ensemble Kalman filter update step
Kovalenko, Andrey; Mannseth, Trond; Nævdal, Geir (Peer reviewed; Journal article, 2012)In recent years, data assimilation techniques have been applied to an increasingly wider specter of problems. Monte Carlo variants of the Kalman filter, in particular, the ensemble Kalman filter (EnKF), have gained significant ...