Recent additions

  • Fluid-Structure Interaction (FSI) Modelling of Aquaculture Net Cage 

    Myrli, Odd Einar; Khawaja, Hassan (Journal article; Peer reviewed, 2019)
    The number of good sites in less exposed locations for aquaculture farming is limited. Trends are now that the fish cages are increasing in both width and depth, as well as more weather-exposed locations, are taken into use. As the net cages continue to increase in size, so does the material costs. The design of the sea cages should be modified for safe and reliable use in remote offshore locations. ...
  • A multi-objective mathematical programming for sustainable reverse logistics network design. Part II: Model application and analysis 

    Yu, Hao; Solvang, Wei Deng; Solvang, Bjørn (Peer reviewed; Chapter; Bokkapittel, 2016-02)
    Reverse logistics has received more and more attention during the past decade due to the increasing public awareness of sustainable development. Because of the fluctuation in both quantity and quality of the reverse material flow, design and planning of reverse logistics network is much more complicated compared with the forward ones. Therefore, it is important to develop decision support tools for ...
  • Energieffektive glasskonstruksjoner 

    Sokolova, Marina (Master thesis; Mastergradsoppgave, 2017-06-08)
    Rapporten tar for seg vurdering av hvor stort varmetapet gjennom vinduene kan bli ved ulike vindustyper, og hvordan forskjellige vindusløsninger påvirker boligens energibehov. Det teoretiske grunnlaget tar for seg former for varmetransport, energioverføring gjennom glasset og glassruter, samt måter å forbedre varmeisolasjonsevnen på.
  • Atomized feedback, an approach to automatic formative assessment 

    Steen, Arild; Movik, Hans Richard (Peer reviewed; Chapter, 2017-11)
    In this article, we describe an approach to give automatic formative evaluation by atomizing the feedback. The mechanics in this approach is a large number of multiple-choice tests. The multiplechoice tests are used as voluntary assignments and gives controlled progression by releasing the tests in an order. Instruction is in the spirit of flipped classroom with short video lectures accompanied by ...
  • Rescue of stranded persons. C18. Rescue of stranded passengers in the Arctic 

    Meidell, Annette; Olsen, Steve (Forskningsrapport; Chapter, 2018-12)
    Since we (the authors) could not be a part of the whole SARex 3 exercise this year, we joined the expedition later than the rest of the participants. We gladly accepted the invitation from the Governor of Svalbard, Kjerstin Askholt, and her staff in Longyearbyen to join their service vessel, MS Polarsyssel, to meet The Norwegian Coast Guard’s vessel, (NOCGV) Svalbard, at the location where the ...
  • Control of Airborne Noise Generated in the Cavities of a T-Slotted Aluminum Cylindrical Column 

    Mustafa, Mohamad Y.; Yizhong, Xu; Sørensen, Bjørn Reidar; Santos, José; Al-Mahadin, Aziz (Peer reviewed; Chapter, 2018-06-11)
    This paper presents a study of airborne noise generated by a T-slotted cylindrical aluminum hollow column with six slots of the type used for the construction of communication towers. Noise is a very distracting phenomena and an environmental concern caused by various sources. Noise pollution is becoming more severe with the introduction of massive human activities and the use of heavy machineries, ...
  • On geometric construction of some power means 

    Høibakk, Ralph; Lukkassen, Dag; Persson, Lars Erik; Meidell, Annette (Journal article; Peer reviewed, 2018-11-27)
    In the homogenization theory, there are many examples where the effective conductivities of composite structures are power means of the local conductivities. The main aim of this paper is to initiate research concerning geometric construction of some power means of three or more variables. We contribute by giving methods for the geometric construction of the harmonic mean $ P_{-1} $ and the arithmetic ...
  • A sharp boundedness result for restricted maximal operators of Vilenkin-Fourier series on martingale Hardy spaces 

    Blahota, Istvan; Nagy, Karoly; Persson, Lars Erik; Tephnadze, George (Journal article; Peer reviewed, 2018-09-20)
    The restricted maximal operators of partial sums with respect to bounded Vilenkin systems are investigated. We derive the maximal subspace of positive numbers, for which this operator is bounded from the Hardy space H p to the Lebesgue space L p for all 0<p≤1 . We also prove that the result is sharp in a particular sense.
  • Engineering students' instrumental approaches to mathematics; some positive characteristics 

    Rensaa, Ragnhild Johanne (Journal article; Peer reviewed, 2018)
    The present paper presents three deliberately chosen mathematical episodes observed in a class of engineering students taking a basic calculus course. By drawing on analyses of instrumental and relational learning strategies, the episodes are shown to illustrate instrumental approaches indicated by the students. The paper discusses positive characteristics about these approaches while further data ...
  • Framework for Modeling and Simulation of Household Appliances 

    Bjerknes Nilsen, Christian; Hoff, Bjarte; Østrem, Trond (Peer reviewed; Chapter, 2018-12-31)
    This paper describes a framework for simulating household appliances in Simulink. Typical Norwegian household equipment have been analyzed based on their characteristic behavior, to establish the requirement for synthesizing and recreating their current waveform, harmonic currents and phase shift. Both detailed simulation of the current waveform and RMS currents for simulation over longer time periods ...
  • Fuel cell technology application for Dubai rail systems 

    Mustafa, Mohamad; Al-Mahadin, Aziz; Kanstad, Bjørn Eirik; Calay, Rajnish K (Peer reviewed; Chapter, 2018-06-11)
    Heat engines, such as internal combustion engines, have significant adverse effects on the environment due to their heat and harmful emissions. In addition, they are dependent on energy from fossil resources, which are depleting rapidly and they are not being properly utilized due to the relatively low efficiency of heat engines usually expressed by Carnot's efficiency. The low temperature direct ...
  • Utilizing fuel cell technology for Dubai Roads and Transport Authority (RTA) 

    Al-Mahadin, Aziz; Mustafa, Mohamad (Peer reviewed; Chapter, 2018-06-11)
    The need for developing environmentally friendly and sustainable energy sources is globally evident. This is due to two main reasons: Fossil fuels will continue to supply energy demands for only a few more decades and the amount of pollution generated due to fossil fuels is exceeding acceptable limits. One very promising clean energy converter is the fuel cell (FC). Fuel cells have the ability to ...
  • Modeling and Attitude Control of Satellites in Elliptical Orbits 

    Oland, Espen (Peer reviewed; Chapter, 2018-11-05)
    The attitude determination and control system (ADCS) for spacecraft is responsible for determining its orientation using sensor measurements and then applying actuation forces to change the orientation. This chapter details the different components required for a complete attitude determination and control system for satellites moving in elliptical orbits. Specifically, the chapter details the orbital ...
  • A value chain analysis for bioenergy production from biomass and biodegradable waste: a case study in Northern Norway 

    Yu, Hao; Roman, Elisabeth; Solvang, Wei Deng (Peer reviewed; Chapter, 2018-09-12)
    During the past decades, the concerns of the depletion of fossil fuels and global warming caused by excess GHG emissions have become the most important driving force for the development and utilization of renewable energy resources. The successful experiences from the EU-28 have proved that bioenergy production from biomass and biodegradable waste is the most reliable and promising solution in ...
  • Feasibility of Computational Fluid Dynamics for Analyzing Airflow around Porous Fences 

    Xu, Yizhong; Calay, Rajnish K; Mustafa, Mohamad (Journal article; Peer reviewed, 2019-01-19)
    This article presents using the computational fluid dynamics (CFD) modeling to analyze the flow around porous fences. The feasibility of applying 2D and 3D models was assessed with respect to corresponding wind tunnel experiments. Comparisons between the flow structures on leeward of the fence as predicted by CFD models and the wind tunnel measurements were discussed. Velocity values for the two ...
  • Resolvent bounds for jump generators 

    Kondratiev, Yuri; Molchanov, Stanislav; Piatnitski, Andrey; Zhizhina, Elena (Journal article; Peer reviewed; Tidsskriftartikkel, 2016-12-02)
    The paper deals with jump generators with a convolution kernel. Assuming that the kernel decays either exponentially or polynomially, we prove a number of lower and upper bounds for the resolvent of such operators. In particular we focus on sharp estimates of the resolvent kernel for small values of the spectral parameter. We consider two applications of these results. First we obtain pointwise ...
  • 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 ...
  • Asymptotic Behaviour of Ground States for Mixtures of Ferromagnetic and Antiferromagnetic Interactions in a Dilute Regime 

    Braides, Andrea; Causin, Andrea; Piatnitski, Andrey; Solci, Margherita (Journal article; Peer reviewed, 2018-04-30)
    We consider randomly distributed mixtures of bonds of ferromagnetic and antiferromagnetic type in a two-dimensional square lattice with probability 1−p 1−p and p, respectively, according to an i.i.d. random variable. We study minimizers of the corresponding nearest-neighbour spin energy on large domains in Z 2 Z2 . We prove that there exists p 0 p0 such that for p≤ p 0 p≤p0 such ...
  • Steady States, Fluctuation-Dissipation Theorems and Homogenization for Reversible Diffusions in a Random Environment 

    Mathieu, P; Piatnitski, A (Journal article; Peer reviewed; Tidsskriftartikkel, 2018-04-02)
    Prolongating our previous paper on the Einstein relation, we study the motion of a particle diffusing in a random reversible environment when subject to a small external forcing. In order to describe the long time behavior of the particle, we introduce the notions of steady state and weak steady state. We establish the continuity of weak steady states for an ergodic and uniformly elliptic environment. ...
  • Pointwise estimates for heat kernels of convolution-type operators 

    Grigor'yan, Alexander; Kondratiev, Yuri; Piatnitski, Andrey; Zhizhina, Elena (Journal article; Peer reviewed; Tidsskriftartikkel, 2018-04-16)
    We study the large‐time behaviour of the fundamental solution of parabolic equations with an elliptic part being non‐local convolution‐type operator. We assume that this operator is a generator of a Markov jump process, and that its convolution kernel decays at least exponentially at infinity. The fundamental solution shows rather different asymptotic behaviour depending on whether | x | ≲ t , or t ...

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