Nye registreringer

  • 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 ...
  • Overview of modern teaching equipment that supports distant learning 

    Horvath, Csongor Mark; Thomessen, Trygve; Sziebig, Gabor (Journal article; Peer reviewed, 2018)
    Laboratory is a key element of engineering and applied sciences educational systems. With the development of Internet and connecting IT technologies, the appearance of remote laboratories was inevitable. Virtual laboratories are also available; they place the experiment in a simulated environment. However, this writing focuses on remote experiments not virtual ones. From the students’ point ...
  • Dynamic plastic response of beams subjected to localised pulse loads 

    Thil, Nicolas; Mehreganian, Navid; Moatamedi, Mojtaba; Louca, Luke A.; Soleiman Fallah, Arash (Journal article; Peer reviewed, 2018-10-31)
    Localised blast loads give rise to high gradients of overpressure detrimental to structural elements as beams and plates. This article presents an analytical study on the dynamic plastic response of beams made of a ductile metallic material due to close-in pulse pressure loading. The close-in pressure load is characterised by a spatially varying function constant over a central region and exponentially ...
  • Hardy-type inequalities in fractional h-discrete calculus 

    Persson, Lars Erik; Oinarov, Ryskul; Shaimardan, Serikbol (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-04-04)
    The first power weighted version of Hardy’s inequality can be rewritten as [<i>mathematical formula</i>] where the constant <i>C</i> =[<i>p</i> / <i>p</i> - <i><b>a</b></i> - 1]<sup><i>p</i></sup> is sharp. This inequality holds in the reversed direction when<math xmlns="http://www.w3.org/1998/Math/MathML"> <mn>0</mn> <mo>&#x2264;<!-- ≤ --></mo> <mi><i>p</i></mi> <mo>&lt;</mo> <mn>1</mn> ...
  • Location-based analysis and optimization of service network performance: A case study 

    Yang, Shuo; Yu, Hao; Solvang, Wei Deng (Peer reviewed; Book; Chapter, 2018-05-07)
    The location problem of service network has been extensively focused by researchers in operational research due to the difficulty in balancing the level of service and efficiency. On the one hand, installing a large number of service facilities within the service network improves availability and responsiveness to customer demands, but it also increases the investment and operating cost. While on ...
  • Review of Icing Effects on Wind Turbine in Cold Regions 

    Virk, Muhammad; Afzal, Faizan (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-12-05)
    This paper describes a brief overview of main issues related to atmospheric ice accretion on wind turbines installed in cold climate region. Icing has significant effects on wind turbine performance particularly from aerodynamic and structural integrity perspective, as ice accumulates mainly on the leading edge of the blades that change its aerodynamic profile shape and effects its structural dynamics ...
  • Optimization models and methods for sustainable reverse logistics network design 

    Yu, Hao (Doctoral thesis; Doktorgradsavhandling, 2018-11-29)
    With the increased focus on sustainable development and circular economy, as never before, the value recovery and re-creation from the End-of-Use and End-of-Life products has been paid considerable attention by the whole society. Reverse logistics is believed as one of the most effective and promising means for the value recovery of the End-of-Use and End-of-Life products, which is the process for ...
  • A Comparative Study of Different Control Structures for Flight Control with New Results 

    Oland, Espen; Kristiansen, Raymond; Gravdahl, Jan Tommy (Peer reviewed; Book; Chapter, 2018-10-24)
    This paper presents several different control structures that facilitate flight control and does a comparison between them. Specifically, this paper considers command-filtered backstepping, nonlinear dynamic inversion (NDI), and a new decoupled approach that decouples the rotational and translational dynamics by estimating the higher order derivatives of the angle of attack and sideslip angle. The ...
  • A Comparison of Two Location Models in Optimizing the Decision-making on the Relocation Problem of Post Offices at Narvik, Norway 

    Yu, Hao; Solvang, Wei Deng (Peer reviewed; Book; Chapter, 2018)
    Since 2013, the postal service provider in Norway: Posten has implemented a new strategic plan to close their large post offices across the country for improving the cost and operational efficiency. Instead, with the cooperation with large retailers, the local postal service is provided at the Posten sub-branches at some supermarkets. In this paper, an optimization problem for relocating the post ...
  • A comparison of the energy consumption for CO2 compression process alternatives 

    Jackson, Steven; Brodal, Eivind (Journal article; Peer reviewed; Tidsskriftartikkel, 2018)
    The efficient transportation of large volumes of CO2 generally requires pipelines that will operate above the critical pressure of CO2. Since most capture processes release CO2 at low pressure, compression of CO2 from the point of capture to pipeline will generally be required. The compression duty can be achieved using conventional multi-stage compressors or using newer shockwave type compressors. ...
  • Quaternion Path-Following in Three Dimensions for a Fixed-Wing UAV Using Quaternion Blending 

    Andersen, Tom Stian; Kristiansen, Raymond (Peer reviewed; Book; Chapter, 2018-10-29)
    This paper presents a three dimensional guidance strategy for fixed-wing UAVs using quaternions. The algorithm is based on constructing two quaternions, one which makes the UAV fly towards the path and one that makes the UAV follow the path. These two quaternions are then blended together such that the path-following objective is reached. The guidance algorithm is applied to a simple kinematic model ...
  • Studies of some Operators of Harmonic Analysis in certain Function Spaces with Applications to PDEs 

    Lundberg, Staffan (Doctoral thesis; Doktorgradsavhandling, 2018-12-05)
    The study in this PhD thesis aims at development of certain mathematical methods used in applications, in particular, in the study of regularity properties of solutions in various mathematical models described by Partial Differential Equations (PDEs). To this end, we study various operators of harmonic analysis in certain function spaces, since solutions to many PDEs may be expressed in terms of ...
  • Incorporating flexible capacity in the planning of a multi-product multi-echelon sustainable reverse logistics network under uncertainty 

    Yu, Hao; Solvang, Wei Deng (Journal article; Tidsskriftartikkel; Peer reviewed, 2018-07-05)
    With the focus on sustainable development, the value recovery from End-of-Life (EOL) and End-of-Use (EOU) products has been given considerable attention by the whole society. Reverse logistics is the process for value recovery and re-creation through a series of activities, i.e., repair, remanufacturing, recycling and energy recovery. However, due to the stochastic reverse product flow, unstable ...
  • A Reliable Modular Based PV-Battery Hybrid System with Peak Shaving Capability 

    Sohail, Umer; Nademi, Hamed; Norum, Lars Einar (Peer reviewed; Chapter, 2018)
    The driving factors in emerging photovoltaic (PV) systems and battery-energy-storage systems (BESS) are highly scalable feature, modular and flexible structures with superior transformerless performance. The feasibility of Modular Multilevel Converter (MMC) to operate without overall DC-link allows the integration of PV generators and battery strings with its submodules (SMs), whereas each SM acts ...
  • Cascaded Model Predictive Control of Grid Connected Converter with LCL Filter 

    Hoff, Bjarte (Peer reviewed; Book; Chapter, 2018-12-31)
    This paper presents a control strategy for grid connected voltage source converters with LCL filter, based on a cascade of two model predictive controllers (MPC). Despite the attention MPC has received in the research community over the last years, there are still raised question about what advantages such control methods can offer, compared to existing established control strategies. The cascaded ...
  • Human-Robot Collaboration: Task Sharing Through Virtual Reality 

    Shu, Beibei; Sziebig, Gabor; Pieskä, Sakari (Peer reviewed; Book; Chapter, 2018-12-31)
    Collaborative Robots provide many possibilities, when it comes to Human-Robot Collaboration. Until now, these approaches are usually custom made, sensor-integrated solutions, where the robot's safety controller ensures the safety of the human worker. These solutions are according to today's rules and standards. We propose to extend these solutions with including Virtual Realty as a sensor and to ...

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