Recent additions

  • The Tipping Effect of Delayed Interventions on the Evolution of COVID-19 Incidence 

    Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-23)
    We combine infectious disease transmission and the non-pharmaceutical (NPI) intervention response to disease incidence into one closed model consisting of two coupled delay differential equations for the incidence rate and the time-dependent reproduction number. The model contains three parameters, the initial reproduction number, the intervention strength, and the response delay. The response is ...
  • Convergence and completeness for square-well Stark resonant state expansions 

    Juhász, David; Kolesik, Miro; Jakobsen, Per (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-11-02)
    In this paper, we investigate the completeness of the Stark resonant states for a particle in a square-well potential. We find that the resonant state expansions for target functions converge inside the potential well and that the existence of this convergence does not depend on the depth of the potential well, <i>V</i><sub>0</sub>. By analyzing the asymptotic form of the terms in these expansions, ...
  • Constructing a partially transparent computational boundary for UPPE using leaky modes 

    Juhász, Dávid; Jakobsen, Per Kristen (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-08-19)
    In this paper, we introduce a method for creating a transparent computational boundary for the simulation of unidirectional propagation of optical beams and pulses using leaky modes. The key element of the method is the introduction of an artificial-index material outside a chosen computational domain and utilization of the quasi-normal modes associated with such artificial structure. The method is ...
  • Individual-Based Modeling of COVID-19 Vaccine Strategies 

    Skagseth, Håvard Mikal (Master thesis; Mastergradsoppgave, 2021-06-01)
    COVID-19 is a respiratory disease with influenza-like symptoms originating from Wuhan, China, towards the end of 2019. There has been developed multiple vaccines to contain the virus and to protect the most vulnerable people in society. In this thesis we look at two different vaccination strategies to prevent most deaths and years of life lost. We conclude that the safest and most consistent strategy ...
  • Modelling of Viral Disease Risk 

    Hahn, Nico (Mastergradsoppgave; Master thesis, 2021-06-19)
    Covid-19 has had a significant impact on daily life since the initial outbreak of the global pandemic in late 2019. Countries have been affected to varying degrees, depending on government actions and country characteristics such as infrastructure and demographics. Using Norway and Germany as a case study, this thesis aims to determine which factors influence the risk of infection in each country, ...
  • Power Flow Optimization with Graph Neural Networks 

    Hansen, Jonas Berg (Mastergradsoppgave; Master thesis, 2021-06-01)
    Power flow analysis is an important tool in power engineering for planning and operating power systems. The standard power flow problem consists of a set of non-linear equations, which are traditionally solved using numerical optimization techniques, such as the Newton-Raphson method. However, these methods can become computationally expensive for larger systems, and convergence to the global optimum ...
  • Symmetric ideals, Specht polynomials and solutions to symmetric systems of equations 

    Moustrou, Philippe; Riener, Cordian; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-18)
    An ideal of polynomials is symmetric if it is closed under permutations of variables. We relate general symmetric ideals to the so called Specht ideals generated by all Specht polynomials of a given shape. We show a connection between the leading monomials of polynomials in the ideal and the Specht polynomials contained in the ideal. This provides applications in several contexts. Most notably, this ...
  • Instance Segmentation of Microscopic Foraminifera 

    Johansen, Thomas Haugland; Sørensen, Steffen Aagaard; Møllersen, Kajsa; Godtliebsen, Gustav (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-07-16)
    Foraminifera are single-celled marine organisms that construct shells that remain as fossils in the marine sediments. Classifying and counting these fossils are important in paleo-oceanographic and -climatological research. However, the identification and counting process has been performed manually since the 1800s and is laborious and time-consuming. In this work, we present a deep learning-based ...
  • Classification of Simply-Transitive Levi Non-Degenerate Hypersurfaces in C^3 

    Doubrov, Boris; Merker, Joël; The, Dennis (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-06-24)
    Holomorphically homogeneous Cauchy–Riemann (CR) real hypersurfaces M<sup>3</sup>⊂C<sup>2</sup> were classified by Élie Cartan in 1932. In the next dimension, we complete the classification of simply-transitive Levi non-degenerate hypersurfaces M<sup>5</sup>⊂C<sup>3</sup> using a novel Lie algebraic approach independent of any earlier classifications of abstract Lie algebras. Central to our approach ...
  • Real Plane Algebraic Curves 

    González García, Pedro (Master thesis; Mastergradsoppgave, 2021-06-18)
    This master thesis studies several properties of real plane algebraic curves, focusing on the case of even degree. The question of the relative positions of the connected components of real plane algebraic curves originates in Hilbert's sixteenth problem which, despite its prominence, is still open in the case of higher degree curves. The goal of this thesis is an exposition of fundamental ...
  • Trans-dimensional inference over Bayesian neural networks 

    Berezowski, Jonathan (Master thesis; Mastergradsoppgave, 2021-06-03)
    Trans-dimensional Bayesian inference for multi-layer perceptron architectures of varying size by reversible jump Markov chain Monte Carlo is developed and examined for its theoretical and practical merits and considerations. The algorithm features the No-U-Turn Sampler and Hamiltonian Monte Carlo for within-dimension moves, and makes use of a delayed-rejection sampler while exploring a variety of ...
  • Symmetric Ideals 

    Lien, Arne (Mastergradsoppgave; Master thesis, 2021-05-14)
    Polynomials appear in many different fields such as statistics, physics and optimization. However, when the degrees or the number of variables are high, it generally becomes quite difficult to solve polynomials or to optimize polynomial functions. An approach that can often be helpful to reduce the complexity of such problems is to study symmetries in the problems. A relatively new field, that has ...
  • Estimation of Excess Mortality and Years of Life Lost to COVID-19 in Norway and Sweden between March and November 2020 

    Rypdal, Martin Wibe; Rypdal, Kristoffer; Løvsletten, Ola; Sørbye, Sigrunn Holbek; Ytterstad, Elinor; Bianchi, Filippo Maria (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-08)
    We estimate the weekly excess all-cause mortality in Norway and Sweden, the years of life lost (YLL) attributed to COVID-19 in Sweden, and the significance of mortality displacement. We computed the expected mortality by taking into account the declining trend and the seasonality in mortality in the two countries over the past 20 years. From the excess mortality in Sweden in 2019/20, we estimated ...
  • Machine Learning in Chronic Pain Research: A Scoping Review 

    Jenssen, Marit Dagny Kristine; Bakkevoll, Per Atle; Ngo, Phuong; Budrionis, Andrius; Fagerlund, Asbjørn Johansen; Tayefi, Maryam; Bellika, Johan Gustav; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-04-02)
    Given the high prevalence and associated cost of chronic pain, it has a significant impact on individuals and society. Improvements in the treatment and management of chronic pain may increase patients’ quality of life and reduce societal costs. In this paper, we evaluate state-of-the-art machine learning approaches in chronic pain research. A literature search was conducted using the PubMed, IEEE ...
  • Modelling suggests limited change in the reproduction number from reopening Norwegian kindergartens and schools during the COVID-19 pandemic 

    Rypdal, Martin Wibe; Rypdal, Veronika Gjertsen; Jakobsen, Per Kristen; Ytterstad, Elinor; Løvsletten, Ola; Klingenberg, Claus; Rypdal, Kristoffer (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-25)
    <i>Background</i> - To suppress the COVID-19 outbreak, the Norwegian government closed all schools on March 13, 2020. The kindergartens reopened on April 20, and the schools on April 27 and May 11 of 2020. The effect of these measures is largely unknown since the role of children in the spread of the SARS-CoV-2 virus is still unclear. There are only a few studies of school closures as a separate ...
  • De-identifying Swedish EHR text using public resources in the general domain 

    Chomutare, Taridzo; Yigzaw, Kassaye Yitbarek; Budrionis, Andrius; Makhlysheva, Alexandra; Godtliebsen, Fred; Dalianis, Hercules (Journal article; Tidsskriftartikkel; Peer reviewed, 2020)
    Sensitive data is normally required to develop rule-based or train machine learning-based models for de-identifying electronic health record (EHR) clinical notes; and this presents important problems for patient privacy. In this study, we add non-sensitive public datasets to EHR training data; (i) scientific medical text and (ii) Wikipedia word vectors. The data, all in Swedish, is used to train a ...
  • Challenges and opportunities beyond structured data in analysis of electronic health records 

    Tayefi, Maryam; Ngo, Phuong; Chomutare, Taridzo; Dalianis, Hercules; Salvi, Elisa; Budrionis, Andrius; Godtliebsen, Fred (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-14)
    Electronic health records (EHR) contain a lot of valuable information about individual patients and the whole population. Besides structured data, unstructured data in EHRs can provide extra, valuable information but the analytics processes are complex, time-consuming, and often require excessive manual effort. Among unstructured data, clinical text and images are the two most popular and important ...
  • Higher weight spectra of codes from Veronese threefolds 

    Johnsen, Trygve; Verdure, Hugues (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-10-23)
    We study binary linear codes C obtained from the quadric Veronese embedding of P<sup>3</sup> in P<sup>9</sup> over F<sub>2</sub>. We show how one can find the higher weight spectra of these codes. Our method will be a study of the Stanley-Reisner rings of a series of matroids associated to each code <i>C</i>.
  • Joint Invariants of Linear Symplectic Actions 

    Andreassen, Fredrik; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
    We review computations of joint invariants on a linear symplectic space, discuss variations for an extension of group and space and relate this to other equivalence problems and approaches, most importantly to differential invariants.
  • Differential Invariants of Linear Symplectic Actions 

    Jensen, Jørn Olav; Kruglikov, Boris (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-12-07)
    We consider the equivalence problem for symplectic and conformal symplectic group actions on submanifolds and functions of symplectic and contact linear spaces. This is solved by computing differential invariants via the Lie-Tresse theorem.

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