• Homogenization of Levy-type operators with oscillating coefficients 

      Kassmann, Moritz; Piatnitski, Andrey; Zhizhina, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2019-01-05)
      The paper deals with homogenization of Lévy-type operators with rapidly oscillating coefficients. We consider cases of periodic and random statistically homogeneous micro-structures and show that in the limit we obtain a Lévy-operator. In the periodic case we study both symmetric and non-symmetric kernels whereas in the random case we only investigate symmetric kernels. We also address a nonlinear ...
    • Homogenization of Non-Autonomous Operators of Convolution Type in Periodic Media<sup>∗</sup> 

      Piatnitski, Andrei; Zhizhina, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-02-23)
      The paper deals with periodic homogenization problem for a para\-bo\-lic equation whose elliptic part is a convolution type operator with rapidly oscillating coefficients. It is assumed that the coefficients are rapidly oscillating periodic functions both in spatial and temporal variables and that the scaling is diffusive that is the scaling factor of the temporal variable is equal to the square of ...
    • Homogenization of nonisothermal immiscible incompressible two-phase flow in porous media 

      Amaziane, Brahim; Jurak, Murat; Pankratov, Leonid; Piatnitski, Andrey (Journal article; Peer reviewed, 2018-03-15)
      In this paper, we consider nonisothermal two-phase flows through heterogeneous porous media with periodic microstructure. Examples of such models appear in gas migration through engineered and geological barriers for a deep repository for radioactive waste, thermally enhanced oil recovery and geothermal systems. The mathematical model is given by a coupled system of two-phase flow equations, and an ...
    • Homogenization of random Navier–Stokes-type system for electrorheological fluid 

      Piatnitski, Andrey; Zhikov, Vasily (Peer reviewed; Journal article; Tidsskriftsartikkel, 2015-11-19)
      The paper deals with homogenization of Navier–Stokes-type system describing electrorheological fluid with random characteristics. Under non-standard growth conditions we construct the homogenized model and prove the convergence result. The structure of the limit equations is also studied.
    • (Hp− Lp -Type inequalities for subsequences of Nörlund means of Walsh–Fourier series 

      Baramidze, David; Persson, Lars-Erik; Tangrand, Kristoffer Meyer; Tephnadze, George (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-04-07)
    • Investigating the affordances of a flipped mathematics classroom from an activity theoretical perspective 

      Fredriksen, Helge (Journal article; Tidsskriftartikkel; Peer reviewed, 2020-11-20)
      Flipped Classroom as a pedagogical framework has gained popularity at secondary and tertiary levels of mathematics education, but there is a lack of research based on a solid theoretical foundation. This article considers the flipped mathematics classroom from the perspective of affordances and cultural–historical activity theory. The empirical background is based on semi-structured interview data ...
    • Investigating the Polar Code’s function-based requirements for life-saving appliances and arrangements, and the performance of survival equipment in cold climate conditions – test of SOLAS approved desalting apparatus at low temperatures 

      Engtrø, Espen; Sæterdal, Ane (Journal article; Tidsskriftartikkel; Peer reviewed, 2021-02-21)
      As the sea ice extent steadily decreases, the Arctic region is simultaneously experiencing extensive growth in commercial shipping activities, in areas which previously were considered inaccessible for most ships during large periods of the year, increasing the probability of accidents or incidents occurring. <i>The International Code for Ships Operating in Polar Waters (The Polar Code)</i> states ...
    • Irregular luggage classification experiments using data from Tromsø airport 

      Jansson, Andreas Dyrøy; Bremdal, Bernt Arild; Remman, Espen (Chapter; Bokkapittel, 2023-09-22)
      This paper examines the current state-of-the-art in object tracking and detection in the context of baggage handling systems using a variety of technologies, with special interest in image classification. Data collection at Tromsø Airport using simple and inexpensive equipment in order to capture images of different types of luggage will be described. Furthermore, a selection of three relevant ...
    • Isogeometric analysis using a tensor product blending spline construction 

      Kravetc, Tatiana (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-06-01)
      In this paper, we introduce a blending spline type construction into the isogeometric analysis. We consider a general algorithm for solving a number of boundary value problems, including heat equation, wave equation, linear elasticity, etc. The usage of blending spline construction in the isogeometric context mixes standard finite element and NURBS-based approaches while accumulating the benefits ...
    • Lagrangian and ALE Formulations For Soil Structure Coupling with Explosive Detonation 

      Souli, M; Albahkali, E; Shahrour, I; Moatamedi, Mojtaba (Journal article; Tidsskriftartikkel; Peer reviewed, 2017)
      Simulation of Soil-Structure Interaction becomes more and more the focus of computational engineering in civil and mechanical engineering, where FEM (Finite element Methods) for soil and structural mechanics and Finite Volume for CFD (Computational Fluid Dynamics) are dominant. New advanced formulations have been developed for FSI (Fluid Structure Interaction) applications using ALE (Arbitrary ...
    • Large deviations for Markov jump processes in periodic and locally periodic environments 

      Piatnitski, Andrei; Pirogov, Sergei; Zhizhina, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2022-12)
      The paper deals with a family of jump Markov process defined in a medium with a periodic or locally periodic microstructure. We assume that the generator of the process is a zero order convolution type operator with rapidly oscillating locally periodic coefficient and, under natural ellipticity and localization conditions, show that the family satisfies the large deviation principle in the path space ...
    • Limit behaviour of diffusion in high-contrast periodic media and related Markov semigroups 

      Piatnitski, Andrey; Pirogov, S; Zhizhina, Elena (Journal article; Tidsskriftartikkel; Peer reviewed, 2019)
      The goal of the paper is to describe the large time behaviour of a symmetric diffusion in a high-contrast periodic environment and to characterize the limit process under the diffusive scaling. We consider separately the C0 and the L2 settings.
    • Local energy markets as a solution for increased energy efficiency and flexibility 

      Ilieva, Iliana; Bremdal, Bernt Arild; de la Nieta Lopez, A.A.S.; Simonsen, S.H. (Journal article; Peer reviewed, 2019)
      With increasing share of distributed renewable energy resources in the grid and arising energy consumer awareness on environmental challenges new market models are sought where energy can be traded in an efficient and end-user centric way. This trend, together with the increasing consciousness on the benefits of local consumption and production has given rise to an increased focus on local energy ...
    • Local Flexibility Market Design for Aggregators Providing Multiple Flexibility Services at Distribution Network Level 

      Olivella-Rosell, Pol; Lloret-Gallego, Pau; Munne-Collado, Ingrid; Villafafila-Robles, Roberto; Sumper, Andreas; Ottesen, Stig Ødegaard; Rajasekharan, Jayaprakash; Bremdal, Bernt Arild (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-02)
      This paper presents a general description of local flexibility markets as a market-based management mechanism for aggregators. The high penetration of distributed energy resources introduces new flexibility services like prosumer or community self-balancing, congestion management and time-of-use optimization. This work is focused on the flexibility framework to enable multiple participants to compete ...
    • Local refinement of ERBS curves 

      Dalmo, Rune (Journal article; Peer reviewed; Chapter, 2013-12-31)
      Expo-rational B-splines (ERBS) provide a blending type construction where local functions at each knot are blended together by infinitely smooth basis functions. In this work we consider some specific ERBS curves that are approximations of parametric curves. We study local refinement to increase flexibility by inserting local control curves at points of interest on the ERBS curve. Inserting knots ...
    • Mapping Marine Macroalgae along the Norwegian Coast Using Hyperspectral UAV Imaging and Convolutional Nets for Semantic Segmentation 

      Skjelvareid, Martin Hansen; Rinde, Eli; Hancke, Kasper; Blix, Katalin; Hoarau, Galice Guillaume (Journal article; Tidsskriftartikkel; Peer reviewed, 2023-10-20)
      Marine macroalgae form underwater "blue forests" with several important functions. Hyperspectral imaging from unmanned aerial vehicles provides a rich set of spectral and spatial data that can be used to map the distribution of such macroalgae. Results from a study using 81 annotated hyper-spectral images from the Norwegian coast are presented. A U-net convolutional network was used for classification, ...
    • Market Study on Inspection and Maintenance Robotics in Norway - Suppliers, Market Needs and Challenges 

      Merz, Mariann; Transeth, Aksel Andreas; Evjemo, Linn Danielsen; Kelasidi, Eleni (Research report; Forskningsrapport, 2023-09-01)
      New and more complex industrial applications of robotic systems for inspection and maintenance (I&M) purposes are enabled by the continuous improvements to the system capabilities. Key factors that fuel this development are advancements in Artificial Intelligence (AI), improvements of sensor technology, miniaturization and cost reduction of components (including motors, batteries, processors and ...
    • Matrix factorization of multivariate Bernstein polynomials 

      Dalmo, Rune (Journal article; Peer reviewed; Tidsskriftartikkel, 2015)
      Ordinary univariate Bernstein polynomials can be represented in matrix form using factor matrices. In this paper we present the definition and basic properties of such factor matrices extended from the univariate case to the general case of arbitrary number of variables by using barycentric coordinates in the hyper-simplices of respective dimension. The main results in the paper are related to the ...
    • MCSINC. Summarising the main findings of work package 1: Demands and requirements for machine sensing infrastructure. 

      Venæs, Janne; Sande, André Bekkevold; Tangrand, Kristoffer Meyer; Seter, Hanne; Arnesen, Petter (Research report; Forskningsrapport, 2023)
      The main objective of the MCSINC project is to identify the opportunities and challenges with Al-based machine vision of road infrastructure under Nordic conditions. Work package 1 focuses specifically on "Demands and requirements for machine sensing infrastructure". This project report summarises the work done in work package 1 in the MCSINC-project: a state of the art on machine sensing under ...
    • Multi-agent Reinforcement Learning for Structured Symbolic Music Generation 

      Dadman, Shayan; Bremdal, Bernt Arild (Chapter; Bokkapittel, 2023-07-12)
      Generating structured music using deep learning methods with symbolic representation is challenging due to the complex relationships between musical elements that define a musical composition. Symbolic representation of music, such as MIDI or sheet music, can help overcome some of these challenges by encoding the music in a format that allows manipulation and analysis. However, the symbolic ...