Results for "Aleck Johnsen"

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A manually-checkable proof for the NP-hardness of 11-color pattern self-assembly tile set synthesisSep 04 2014Patterned self-assembly tile set synthesis (PATS) aims at finding a minimum tile set to uniquely self-assemble a given rectangular (color) pattern. For k >= 1, k-PATS is a variant of PATS that restricts input patterns to those with at most $k$ colors. ... More
Inference from Auction PricesFeb 19 2019Econometric inference allows an analyst to back out the values of agents in a mechanism from the rules of the mechanism and bids of the agents. This paper proposes the problem of inferring the values of agents in a mechanism from the social choice function ... More
Dashboard Mechanisms for Online MarketplacesMay 14 2019This paper gives a theoretical model for design and analysis of mechanisms for online marketplaces where a bidding dashboard enables the bid-optimization of long-lived agents. We assume that a good allocation algorithm exists when given the true values ... More
Computing Minimum Tile Sets to Self-Assemble Colors PatternsApr 10 2014Patterned self-assembly tile set synthesis (PATS) aims at finding a minimum tile set to uniquely self-assemble a given rectangular color pattern. For $k \ge 1$, $k$-PATS is a variant of PATS that restricts input patterns to those with at most $k$ colors. ... More
On the Theory of Type 1,1-OperatorsOct 14 2016This dissertation concerns the pseudo-differential operators of type 1,1. These have been known especially since around 1980, when it was shown that they play an important role in the treatment of fully non-linear partial differential equations. First ... More
Fundamental Results for Pseudo-Differential Operators of Type $\mathbf{1},\mathbf{1}$Aug 15 2016This paper develops some deeper consequences of an extended definition, proposed previously by the author, of pseudo-differential operators that are of type $1,1$ in H\"ormander's sense. Thus, it contributes to the long-standing problem of creating a ... More
On the Theory of Type 1,1-OperatorsOct 14 2016Mar 20 2017This dissertation concerns the pseudo-differential operators of type 1,1. These have been known especially since around 1980, when it was shown that they play an important role in the treatment of fully non-linear partial differential equations. First ... More
Regularity results and parametrices of semi-linear boundary problems of product typeMar 17 2017This short note describes the benefit one obtains from a specific construction of a family of parametrices for a class of elliptic boundary value problems perturbed by non-linear terms of product type. The construction is based on the Boutet de Monvel ... More
A class of well-posed parabolic final value problemsApr 10 2019This paper focuses on parabolic final value problems, and well-posedness is proved for a large class of these. The clarification is obtained from Hilbert spaces that characterise data that give existence, uniqueness and stability of the solutions. The ... More
Simple proofs of nowhere-differentiability for Weierstrass's function and cases of slow growthOct 20 2016Using a few basics from integration theory, a short proof of nowhere-differentiability of Weierstrass functions is given. Restated in terms of the Fourier transformation, the method consists in principle of a second microlocalisation, which is used to ... More
On the spectral properties of Witten-Laplacians, their range projections and Brascamp-Lieb's inequalityMar 29 2017Mar 30 2017A study is made of an integral identity of Helffer and Sj{\"o}strand, which for some class of probability measures yields a formula for the covariance of two functions (of a stochastic variable). In comparison with the Brascamp--Lieb inequality, this ... More
Type 1,1-operators defined by vanishing frequency modulationJan 12 2017This paper presents a general definition of pseudo-differential operators of type $1,1$; the definition is shown to be the largest one that is both compatible with negligible operators and stable under vanishing frequency modulation. Elaborating counter-examples ... More
$L_p$-Theory of Type $1,1$-OperatorsSep 26 2016This is a continuation of recent work on the general definition of pseudo-differential operators of type $1,1$, in H\"ormander's sense. Continuity in $L_p$-Sobolev spaces and H\"older--Zygmund spaces, and more generally in Besov and Lizorkin--Triebel ... More
Pointwise estimates of pseudo-differential operatorsSep 23 2016As a new technique it is shown how general pseudo-differential operators can be estimated at arbitrary points in Euclidean space when acting on functions $u$ with compact spectra. The estimate is a factorisation inequality, in which one factor is the ... More
Regularity properties of semilinear boundary problems in Besov and Triebel--Lizorkin spacesApr 24 2017Semi-linear elliptic boundary problems with non-linearities of product type are considered, in particular the stationary Navier--Stokes equations. Regularity and existence results are dealt with in the Besov and Triebel--Lizorkin spaces, and it is explained ... More
Domains of type 1,1 operators: a case for Triebel--Lizorkin spacesFeb 07 2017Pseudo-differential operators of type 1,1 are proved continuous from the Triebel--Lizorkin space $F^d_{p,1}$ to $L_p$ for $1\le p<\infty$, when of order d, and this is the largest possible domain among the Besov and Triebel--Lizorkin spaces. H\"ormander's ... More
Characterisation of Log-Convex Decay in Non-Selfadjoint DynamicsJun 28 2018Dec 17 2018The short-time and global behaviour are studied for an autonomous linear evolution equation, which is defined by a generator inducing a uniformly bounded holomorphic semigroup in a Hilbert space. A general necessary and sufficient condition is introduced ... More
Rank Two Bundles on Algebraic Curves and Decoding of Goppa CodesAug 21 1996Jan 14 2003We study a connection between two topics: Decoding of Goppa codes arising from an algebraic curve, and rank two extensions of certain line bundles on the curve.
Traces of Besov spaces revisitedMar 22 2017For the trace of Besov spaces $B^s_{p,q}$ onto a hyperplane, the borderline case with $s=\frac{n}{p}-(n-1)$ and $0<p<1$ is analysed and a new dependence on the sum-exponent $q$ is found. Through examples the restriction operator defined for $s$ down to ... More
Spin-dynamic field coupling in strongly THz driven semiconductors : local inversion symmetry breakingJan 12 2000We study theoretically the optics in undoped direct gap semiconductors which are strongly driven in the THz regime. We calculate the optical sideband generation due to nonlinear mixing of the THz field and the near infrared probe. Starting with an inversion ... More
Parametrices and exact paralinearisation of semi-linear boundary problemsDec 01 2016The subject is parametrices for semi-linear problems, based on parametrices for linear boundary problems and on non-linearities that decompose into solution-dependent linear operators acting on the solutions. Non-linearities of product type are shown ... More
Pointwise multiplication of Besov and Triebel--Lizorkin spacesSep 08 2017It is shown that para-multiplication applies to a certain product $\pi(u,v)$ defined for appropriate temperate distributions $u$ and $v$. Boundedness of $\pi(\cdot,\cdot)$ is investigated for the anisotropic Besov and Triebel--Lizorkin spaces, more precisely ... More
Domains of pseudo-differential operators: a case for the Triebel--Lizorkin spacesFeb 03 2017The main result is that every pseudo-differential operator of type 1,1 and order $d$ is continuous from the Triebel--Lizorkin space $F^d_{p,1}$ to $L_p$, $1\le p<\infty$, and that this is optimal within the Besov and Triebel--Lizorkin scales.The proof ... More
Elliptic boundary problems and the Boutet de Monvel calculus in Besov and Triebel--Lizorkin spacesApr 27 2017The Boutet de Monvel calculus of pseudo-differential boundary operators is generalised to the full scales of Besov and Triebel--Lizorkin spaces (though with finite integral exponents for the latter). The continuity and Fredholm properties proved here ... More
Generalized Hamming weights for almost affine codesJan 07 2016We define generalized Hamming weights for almost affine codes. We show how various aspects and applications of generalized Hamming weights for linear codes, such as Wei duality, generalized Kung's bound, profiles, connection to wire-tap channels of type ... More
Higher weight spectra of Veronese codesApr 16 2019We study q-ary linear codes C obtained from Veronese surfaces over finite fields. We show how one can find the higher weight spectra of these codes, or equivalently, the weight distribution of all extension codes of C over all field extensions of the ... More
High-order schemes for the Euler equations in cylindrical/spherical coordinatesJan 17 2017We consider implementations of high-order finite difference Weighted Essentially Non-Oscillatory (WENO) schemes for the Euler equations in cylindrical and spherical coordinate systems with radial dependence only. The main concern of this work lies in ... More
Stanley-Reisner resolution of constant weight linear codesApr 12 2012Jan 03 2013Given a constant weight linear code, we investigate its weight hierarchy and the Stanley-Reisner resolution of its associated matroid regarded as a simplicial complex. We also exhibit conditions on the higher weights sufficient to conclude that the code ... More
On the trace problem for Triebel--Lizorkin spaces with mixed normsFeb 02 2017The subject is traces of Sobolev spaces with mixed Lebesgue norms on Euclidean space. Specifically, restrictions to the hyperplanes given by the first and last coordinates are applied to functions belonging to quasi-homogeneous, mixed-norm Lizorkin--Triebel ... More
Semi-linear boundary problems of composition type in $L_p$-related spacesApr 21 2017The class of problems treated here are elliptic partial differential equations with a homogeneous boundary condition and a non-linear perturbation obtained by composition with a fixed smooth function. The existence of solutions is obtained from the Leray--Schauder ... More
Flags of almost affine codesApr 10 2017We describe a two-party wire-tap channel of type II in the framework of almost affine codes. Its cryptological performance is related to some relative profiles of a pair of almost affine codes. These profiles are analogues of relative generalized Hamming ... More
A direct proof of Sobolev embeddings for quasi-homogeneous Lizorkin--Triebel spaces with mixed normsFeb 03 2017The article deals with a simplified proof of the Sobolev embedding theorem for Lizorkin--Triebel spaces (that contain the $L_p$-Sobolev spaces $H^s_p$ as special cases). The method extends to a proof of the corresponding fact for general Lizorkin--Triebel ... More
Hamming weights and Betti numbers of Stanley-Reisner rings associated to matroidsAug 16 2011Jan 02 2013To each linear code over a finite field we associate the matroid of its parity check matrix. We show to what extent one can determine the generalized Hamming weights of the code (or defined for a matroid in general) from various sets of Betti numbers ... More
Homogenization of the heat equation with a vanishing volumetric heat capacitySep 28 2018This paper is devoted to the homogenization of the heat conduction equation, with a homogeneous Dirichlet boundary condition, having a periodically oscillating thermal conductivity and a vanishing volumetric heat capacity. A homogenization result is established ... More
Navigating a maze differently - a user studyMay 23 2018Sep 20 2018Navigating spaces is an embodied experience. Examples can vary from rescue workers trying to save people from natural disasters; a tourist finding their way to the nearest coffee shop, or a gamer solving a maze. Virtual reality allows these experiences ... More
Generalized Hamming weights for almost affine codesJan 07 2016Mar 17 2017We define generalized Hamming weights for almost affine codes. We show how various aspects and applications of generalized Hamming weights for linear codes, such as Wei duality, generalized Kung's bound, profiles, connection to wire-tap channels of type ... More
Higher weight spectra of Veronese codesApr 16 2019Apr 25 2019We study q-ary linear codes C obtained from Veronese surfaces over finite fields. We show how one can find the higher weight spectra of these codes, or equivalently, the weight distribution of all extension codes of C over all field extensions of the ... More
On parabolic final value problems and well-posednessAug 23 2017Feb 14 2018We prove that a large class of parabolic final value problems is well posed.This results via explicit Hilbert spaces that characterise the data yielding existence, uniqueness and stability of solutions. This data space is the graph normed domain of an ... More
Dynamical Franz-Keldysh effectDec 12 1995We introduce and analyze the properties of dynamical Franz-Keldysh effect, i.e. the change of density-of-states, or absorption spectra, of semiconductors under the influence of {\it time-dependent} electric fields. In the case of a harmonic time-dependence, ... More
Rational Curves in Calabi-Yau ThreefoldsJul 01 2003Jan 12 2005We study the set of rational curves of a certain topological type in general members of certain families of Calabi-Yau threefolds. For some families we investigate to what extent it is possible to conclude that this set is finite. For other families we ... More
K3 projective models in scrollsAug 28 2001Apr 12 2005We study the projective models of complex K3 surfaces polarized by a line bundle L such that all smooth curves in |L| have non-general Clifford index. Such models are in a natural way contained in rational normal scrolls. We use this study to classify ... More
Rational curves of degree at most 9 on a general quintic threefoldOct 30 1995Mar 01 1996We prove the following form of the Clemens conjecture in low degree. Let $d\le9$, and let $F$ be a general quintic threefold in $\IP^4$. Then (1)~the Hilbert scheme of rational, smooth and irreducible curves of degree $d$ on $F$ is finite, nonempty, and ... More
Density Matrix Functional Calculations for Matter in Strong Magnetic Fields: I. Atomic PropertiesMar 21 1996We report on a numerical study of the density matrix functional introduced by Lieb, Solovej and Yngvason for the investigation of heavy atoms in high magnetic fields. This functional describes {\em exactly} the quantum mechanical ground state of atoms ... More
Quasienergy Spectroscopy of ExcitonsMar 12 1999Jul 30 1999We theoretically study nonlinear optics of excitons under intense THz irradiation. In particular, the linear near infrared absorption and resonantly enhanced nonlinear sideband generation are described. We predict a rich structure in the spectra which ... More
Probing Bose-Einstein Condensation of Excitons with Electromagnetic RadiationJun 07 2000We examine the absorption spectrum of electromagnetic radiation from excitons, where an exciton in the $1s$ state absorbs a photon and makes a transition to the $2p$ state. We demonstrate that the absorption spectrum depends strongly on the quantum degeneracy ... More
Linear optical absorption spectra of mesoscopic structures in intense THz fields: free particle propertiesApr 09 1997We theoretically study the effect of THz radiation on the linear optical absorption spectra of semiconductor structures. A general theoretical framework, based on non-equilibrium Green functions, is formulated, and applied to the calculation of linear ... More
Final value problems for parabolic differential equations and their well-posednessJul 07 2017May 14 2018This article concerns the basic understanding of parabolic final value problems, and a large class of such problems is proved to be well posed. The clarification is obtained via explicit Hilbert spaces that characterise the possible data, giving existence, ... More
Decoding of scroll codesMay 21 2007We define and study a class of codes obtained from scrolls over curves of any genus over finite fields. These codes generalize Goppa codes in a natural way, and the orthogonal complements of these codes belong to the same class. We show how syndromes ... More
Wavelet transforms for homogeneous mixed-norm Triebel--Lizorkin spacesAug 12 2016Mar 29 2017Homogeneous mixed-norm Triebel--Lizorkin spaces are introduced and studied with the use of a discrete wavelet transformation, the so-called $\varphi$-transform. This extends the classical $\varphi$-transform approach introduced by Frazier and Jawerth ... More
Toward Clemens' Conjecture in degrees between 10 and 24Jan 23 1996Mar 22 1996We introduce and study a likely condition that implies the following form of Clemens' conjecture in degrees $d$ between 10 and 24: given a general quintic threefold $F$ in complex $\IP^4$, the Hilbert scheme of rational, smooth and irreducible curves ... More
A Polymatroid Approach to Generalized Weights of Rank Metric CodesApr 03 2019We consider the notion of a $(q,m)$-polymatroid, due to Shiromoto, and the more general notion of $(q,m)$-demi-polymatroid, and show how generalized weights can be defined for them. Further, we establish a duality for these weights analogous to Wei duality ... More
A generalization of weight polynomials to matroidsNov 25 2013Nov 12 2015Generalizing polynomials previously studied in the context of linear codes, we define weight polynomials and an enumerator for a matroid $M$. Our main result is that these polynomials are determined by Betti numbers associated with graded minimal free ... More
Magnetisation reorientation due to superconducting transition in heavy metal heterostructuresJan 02 2019Jan 04 2019Recent theoretical and experimental work has demonstrated how the superconducting critical temperature $(T_c)$ can be modified by rotating the magnetisation of a single homogeneous ferromagnet proximity-coupled to the superconducting layer. This occurs ... More
Schubert Unions in Grassmann VarietiesMar 07 2005We study subsets of Grassmann varieties G(l,m) over a field F, such that these subsets are unions of Schubert cycles, with respect to a fixed flag. We study the linear spans of, and in case of positive characteristic, the number of points on such unions ... More
Anisotropic Lizorkin--Triebel Spaces with Mixed Norms --- Traces on Smooth BoundariesAug 16 2016This article deals with trace operators on anisotropic Lizorkin--Triebel spaces with mixed norms over cylindrical domains with smooth boundary. As a preparation we include a rather self-contained exposition of Lizorkin--Triebel spaces on manifolds and ... More
Wavelet transforms for homogeneous mixed-norm Triebel--Lizorkin spacesAug 12 2016Homogeneous mixed-norm Triebel--Lizorkin spaces are introduced and studied with the use of a discrete wavelet transformation, the so-called $\varphi$-transform. This extends the classical $\varphi$-transform approach introduced by Frazier and Jawerth ... More
Two Steps to ObfuscationFeb 12 2014This note addresses the historical antecedents of the 1998 PageRank measure of centrality. An identity relation links it to 1990-1991 models of Friedkin and Johnsen.
Traces of anisotropic Besov--Lizorkin--Triebel spaces---a complete treatment of the borderline casesMar 20 2017Including the previously untreated borderline cases, the trace spaces in the distributional sense of the Besov--Lizorkin--Triebel spaces are determined for the anisotropic (or quasi-homogeneous) version of these classes. The ranges of the trace are in ... More
Isolated rational curves on K3-fibered Calabi-Yau threefoldsOct 08 1997Jan 24 2001We study each of the 16 types of complete intersection Calabi-Yau threefolds in projective n-space times the projective line, for various n, and prove existence of isolated rational curves of bidegree (d,0) for all positive integers d on a general threefold ... More
A generalization of Kung's theoremMay 21 2015Oct 02 2015We give a generalization of Kung's theorem on critical exponents of linear codes over a finite field, in terms of sums of extended weight polynomials of linear codes. For all i=k+1,...,n, we give an upper bound on the smallest integer m such that there ... More
Anisotropic, Mixed-Norm Lizorkin--Triebel Spaces and Diffeomorphic MapsAug 16 2016This article gives general results on invariance of anisotropic Lizorkin--Triebel spaces with mixed norms under coordinate transformations on Euclidean space, open sets and cylindrical domains.
Characterisation by Local Means of Anisotropic Lizorkin--Triebel Spaces with Mixed NormsSep 22 2016This is a contribution to the theory of Lizorkin--Triebel spaces having mixed Lebesgue norms and quasi-homogeneous smoothness. We discuss their characterisation in terms of general quasi-norms based on convolutions. In particular, this covers the case ... More
Betti numbers associated to the facet ideal of a matroidJul 14 2012Jan 06 2015To a matroid M with n edges, we associate the so-called facet ideal F(M) generated by monomials corresponding to bases of M. We show that the Betti numbers related to an N-graded minimal free resolution of F(M) are determined by the Betti numbers related ... More
Time complexity of concurrent programsNov 16 2015We study the problem of automatically computing the time complexity of concurrent object-oriented programs. To determine this complexity we use intermediate abstract descriptions that record relevant information for the time analysis (cost of statements, ... More
A Type-Safe Model of Adaptive Object GroupsAug 22 2012Services are autonomous, self-describing, technology-neutral software units that can be described, published, discovered, and composed into software applications at runtime. Designing software services and composing services in order to form applications ... More
A continuous stream flash evaporator for the calibration of an IR cavity ring down spectrometer for isotopic analysis of waterSep 01 2014A new technique for high resolution simultaneous isotopic analysis of $\delta^{18}\mathrm{O}$ and $\delta\mathrm{D}$ in liquid water is presented. A continuous stream flash evaporator has been designed that is able to vaporise a stream of liquid water ... More
Modeling Deployment Decisions for Elastic Services with ABSOct 26 2016The use of cloud technology can offer significant savings for the deployment of services, provided that the service is able to make efficient use of the available virtual resources to meet service-level requirements. To avoid software designs that scale ... More
Assumption Commitment Types for Resource Management in Virtually Timed AmbientsJun 22 2018This paper introduces a type system for resource management in the context of nested virtualization. With nested virtualization, virtual machines compete with other processes for the resources of their host environment in order to provision their own ... More
Generalizations of Wei's Duality TheoremOct 12 2009Wei's celebrated Duality Theorem is generalized in several ways, expressed as duality theorems for linear codes over division rings and, more generally, duality theorems for matroids. These results are further generalized, resulting in two Wei-type duality ... More
Lightweight Time Modeling in Timed CreolSep 22 2010Creol is an object-oriented modeling language in which inherently concurrent objects exchange asynchronous method calls. The operational semantics of Creol is written in an actor-based style, formulated in rewriting logic. The operational semantics yields ... More
A wall-function approach for direct precipitation/crystallization fouling in cfd modellingJun 09 2017The main objective of this paper is to present a generic modelling framework, for the diffusive mass transport through the turbulent, reactive boundary layer of multi-component fluid mixtures that precipitate on the wall. The modelling is based on Maxwell-Stefan ... More
EasyInterface: A toolkit for rapid development of GUIs for research prototype toolsFeb 01 2017In this paper we describe EasyInterface, an open-source toolkit for rapid development of web-based graphical user interfaces (GUIs). This toolkit addresses the need of researchers to make their research prototype tools available to the community, and ... More
CFD simulations of turbulent flow in the human upper airwaysJun 08 2017In this paper, investigations are conducted using Reynolds-averaged Navier-Stokes (RANS) turbulence models to investigate the importance of turbulence modelling for nasal inspiration at a constant flow rate of 250 ml/s. Four different, standard turbulence ... More
Contact resistance of quantum tubesJul 02 1999Nov 15 1999We consider the conductance of a quantum tube connected to a metallic contact. The number of angular momentum states that the tube can support depends on the strength of the radial confinement. We calculate the transmission coefficients which yield the ... More
Assumption-Commitment Types for Resource Management in Virtually Timed AmbientsJun 22 2018Apr 12 2019This paper introduces a type system for resource management in the context of nested virtualization. With nested virtualization, virtual machines compete with other processes for the resources of their host environment in order to provision their own ... More
Patient specific numerical simulation of flow in the human upper airways for assessing the effect of nasal surgeryJun 08 2017The study is looking into the potential of using computational fluid dynamics (CFD) as a tool for predicting the outcome of surgery for alleviation of obstructive sleep apnea syndrome (OSAS). From pre- and post-operative computed tomography (CT) of an ... More
Nighttime mesospheric ozone enhancements during the 2002 southern hemispheric major stratospheric warmingJul 31 2018Sudden Stratospheric Warmings (SSW) affect the chemistry and dynamics of the middle atmosphere. Major warmings occur roughly every second winter in the Northern Hemisphere (NH), but has only been observed once in the Southern Hemisphere (SH), during the ... More
Huge Thermoelectric Power Factor: FeSb2 versus FeAs2 and RuSb2Oct 05 2009The thermoelectric power factor of the narrow-gap semiconductor FeSb2 is greatly enhanced in comparison to the isostructural homologues FeAs2 and RuSb2. Comparative studies of magnetic and thermodynamic properties provide evidence that the narrow and ... More
Strong electron correlations in FeSb2: An optical investigation and comparison with RuSb2Dec 15 2010We report investigations of the optical properties of the narrow gap semiconductor FeSb2 in comparison with the structural homolog RuSb2. In the infrared region the latter shows insulating behavior in whole investigated temperature range (10 - 300 K) ... More
On the wall boundary conditions for species-specific mass conservation equations in mathematical modelling of direct precipitation fouling from supersaturated, multi-component fluid mixturesMar 04 2017Mar 21 2017The mathematical modelling of species transport in the turbulent boundary layer of fluids that precipitate on the wall, is an important topic at the heart of one of the biggest challenges in efficient energy utilization in all process industries; namely ... More
Water isotopic ratios from a continuously melted ice core sampleApr 23 2014A new technique for on-line high resolution isotopic analysis of liquid water, tailored for ice core studies is presented. We built an interface between a Wavelength Scanned Cavity Ring Down Spectrometer (WS-CRDS) purchased from Picarro Inc. and a Continuous ... More
Unchanged thermopower enhancement at the semiconductor-metal transition in correlated FeSb$_{2-x}$Te$_x$Feb 01 2011Substitution of Sb in FeSb$_2$ by less than 0.5% of Te induces a transition from a correlated semiconductor to an unconventional metal with large effective charge carrier mass $m^*$. Spanning the entire range of the semiconductor-metal crossover, we observed ... More
Modeling and Simulation of Spark StreamingAug 27 2018Sep 11 2018As more and more devices connect to Internet of Things, unbounded streams of data will be generated, which have to be processed "on the fly" in order to trigger automated actions and deliver real-time services. Spark Streaming is a popular realtime stream ... More
Higher weights of Grassmann codes in terms of properties of Schubert unionsApr 30 2011We describe the higher weights of the Grassmann codes $G(2,m)$ over finite fields ${\mathbb F}_q$ in terms of properties of Schubert unions, and in each case we determine the weight as the minimum of two explicit polynomial expressions in $q$.
Implementation, demonstration and validation of a user-defined wall-function for direct precipitation fouling in ANSYS FluentJun 02 2017In a previous paper (Johnsen et al., 2015) and presentation (Johnsen et al., 2016), we developed and demonstrated a generic modelling framework for the modelling of direct precipitation fouling from multi-component fluid mixtures that become super-saturated ... More
Quantifying Legibility of Indoor Spaces Using Deep Convolutional Neural Networks: Case Studies in Train StationsJan 22 2019Legibility is the extent to which a space can be easily recognized. Evaluating legibility is particularly desirable in indoor spaces, since it has a large impact on human behavior and the efficiency of space utilization. However, indoor space legibility ... More
Time and spectrum-resolving mutiphoton correlator for 300-900 nmJun 17 2014We demonstrate a single-photon sensitive spectrometer in the visible range, which allows us to perform time-resolved and multi-photon spectral correlation measurements. It is based on a monochromator composed of two gratings, collimation optics and an ... More
Granular Rayleigh-Taylor Instability: Experiments and SimulationsJun 01 2007Oct 04 2007A granular instability driven by gravity is studied experimentally and numerically. The instability arises as grains fall in a closed Hele-Shaw cell where a layer of dense granular material is positioned above a layer of air. The initially flat front ... More
Excitation of radial collective modes in a quantum dot: Beyond linear responseNov 13 2013Jul 21 2014We compare the response of five different models of two interacting electrons in a quantum dot to an external short lived radial excitation that is strong enough to excite the system well beyond the linear response regime. The models considered describe ... More
Controlled fabrication of single-walled carbon nanotube electrodes by electron-beam-induced oxidationJun 30 2011The fabrication of metallic single-walled carbon nanotube electrodes separated by gaps of typically 20nm width by electron-beam-induced oxidation is studied within an active device configuration. The tube conductance is measured continuously during the ... More
Reproducible probe-level analysis of the Affymetrix Exon 1.0 ST array with R/BioconductorFeb 15 2013Feb 18 2013The presence of different transcripts of a gene across samples can be analysed by whole-transcriptome microarrays. Reproducing results from published microarray data represents a challenge due to the vast amounts of data and the large variety of pre-processing ... More
An ultrahigh-vacuum cryostat for simultaneous scanning tunneling microscopy and magneto-transport measurements down to 400mKJul 29 2017Jan 17 2018We present the design and calibration measurements of a scanning tunneling microscope setup in a 3He ultrahigh-vacuum cryostat operating at 400 mK with a hold time of 10 days. With 2.70 m in height and 4.70 m free space needed for assembly, the cryostat ... More
Challenges and Recommendations for Preparing HPC Applications for ExascaleMar 24 2015Jun 09 2015While the HPC community is working towards the development of the first Exaflop computer (expected around 2020), after reaching the Petaflop milestone in 2008 still only few HPC applications are able to fully exploit the capabilities of Petaflop systems. ... More
Nitric Oxide Response to the April 2010 Electron Precipitation Event: UsingWACCM andWACCM-DWith andWithout Medium-Energy ElectronsJul 31 2018Energetic electrons from the magnetosphere deposit their energy in the atmosphere and lead to production of nitric oxide (NO) in the mesosphere and lower thermosphere. We study the atmospheric NO response to a geomagnetic storm in April 2010 with WACCM ... More
Time-resolved double-slit experiment with entangled photonsApr 17 2013May 06 2013The double-slit experiment strikingly demonstrates the wave-particle duality of quantum objects. In this famous experiment, particles pass one-by-one through a pair of slits and are detected on a distant screen. A distinct wave-like pattern emerges after ... More
Excitonic Dynamical Franz-Keldysh EffectApr 23 1998The Dynamical Franz-Keldysh Effect is exposed by exploring near-bandgap absorption in the presence of intense THz electric fields. It bridges the gap between the DC Franz- Keldysh effect and multi-photon absorption and competes with the THz AC Stark Effect ... More
Estimation of cold plasma outflow during geomagnetic stormsMay 31 2016Low-energy ions of ionospheric origin constitute a significant contributor to the magnetospheric plasma population. Measuring cold ions is difficult though. Observations have to be done at sufficiently high altitudes and typically in regions of space ... More
Distributed Co-Simulation of Maritime Systems and OperationsJan 04 2017Here, we present the concept of an open virtual prototyping framework for maritime systems and operations that enables its users to develop re-usable component or subsystem models, and combine them in full-system simulations for prototyping, verification, ... More
Spectral Calibration of the Fluorescence Telescopes of the Pierre Auger ObservatorySep 05 2017Oct 02 2017We present a novel method to measure precisely the relative spectral response of the fluorescence telescopes of the Pierre Auger Observatory. We used a portable light source based on a xenon flasher and a monochromator to measure the relative spectral ... More
A targeted search for point sources of EeV photons with the Pierre Auger ObservatoryDec 13 2016Mar 21 2017Simultaneous measurements of air showers with the fluorescence and surface detectors of the Pierre Auger Observatory allow a sensitive search for EeV photon point sources. Several Galactic and extragalactic candidate objects are grouped in classes to ... More