Now showing items 91-100 of 101
Homogenization of nonisothermal immiscible incompressible two-phase flow in porous media
(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
(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
(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
(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 ...
Resolvent bounds for jump generators
(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 ...
Feasibility of Computational Fluid Dynamics for Analyzing Airflow around Porous Fences
(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 ...
Engineering students' instrumental approaches to mathematics; some positive characteristics
(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 ...
A sharp boundedness result for restricted maximal operators of Vilenkin-Fourier series on martingale Hardy spaces
(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.
Review of marine icing and anti-/de-icing systems
(Journal article; Tidsskriftartikkel; Peer reviewed, 2016-08-17)
The aim of this work is to review the phenomenon of icing in marine operations. The focus is on two main sources of icing, namely atmospheric and sea spray. The literature reveals that sea spray icing is the main contributor to marine icing. This work discusses the available ice accretion prediction models on ships and offshore structures. It also reviews the anti-/de-icing technologies that can be ...
Measuring Thickness of Marine Ice Using IR Thermography
(Journal article; Tidsskriftartikkel; Peer reviewed, 2018-09-04)
<p>There are several challenges to operating in a cold climate. Marine icing is one of them, and its mitigation is vital for marine operations.</p> <p>The presented work is a laboratory-scale setup to measure marine ice thickness. The developed methodology can be applied towards de-/anti-icing setups. The method described is based on measuring the average surface temperatures of the marine ice. ...