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  • 301. Larsson, E. K.
    et al.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Söderström, T.
    Identification of continuous-time ARX models from irregularly sampled data2004Report (Other academic)
  • 302. Larsson, E. K.
    et al.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Söderström, T.
    Identification of continuous-time ARX models from irregularly sampled data2007In: IEEE Transactions on Automatic Control, ISSN 0018-9286, E-ISSN 1558-2523, Vol. 52, no 3, p. 417-427Article in journal (Refereed)
  • 303. Larsson, E. K.
    et al.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Söderström, T.
    Practical aspects of continuous-time ARMA system identification2004Report (Other academic)
  • 304. Larsson, E. K.
    et al.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Söderström, T.
    The Cramér-Rao bound for estimation of continuous-time ARX parameters from irregularly sampled data2005Conference paper (Refereed)
  • 305.
    Larsson, Erik K.
    et al.
    Division of Systems and Control, Department of Information Technology, Uppsala University, Sweden .
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Söderström, Torsten
    Division of Systems and Control, Department of Information Technology, Uppsala University, Sweden .
    An overview of important practical aspects of continuous-time ARMA system identification2006In: Circuits, systems, and signal processing, ISSN 0278-081X, E-ISSN 1531-5878, Vol. 25, no 1, p. 17-46Article in journal (Refereed)
    Abstract [en]

    The problem of estimating the parameters in continuous-time autoregressive moving average (ARMA) processes from discrete-time data is considered. Both direct and indirect methods are studied, and similarities and differences are discussed. A general discussion of the inherent difficulties of the problem is given together with a comprehensive study on how the choice of the sampling interval influences the estimation result. A special focus is given to how the Cramer-Rao lower bound depends on the sampling interval.

  • 306.
    Laurenzi, Giulio
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Uppfattning av hårdhet vid ljudreproduktion2013Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    The purpose of this degree work is to try and explain the reasons for the perception of hardness in reproduction of sound. The technique used are analysis of some characteristics of different loudspeakers and some characteristics of the surrounding area where the sound tests have been performed.

    Download full text (pdf)
    Uppfattning av hårdhet i ljud reproduktion - Giulio Laurenzi
  • 307. Lequin, O.
    et al.
    Gevers, M.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bosmans, E.
    Triest, L.
    Iterative Feedback Tuning of PID parameters: Comparison with classical tuning rules2003In: Control Engineering Practice, ISSN 0967-0661, E-ISSN 1873-6939, Vol. 11, no 9, p. 1023-1033Article in journal (Refereed)
  • 308.
    Lerneman, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    RO hantering på ABB, TPE2014Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [sv]

    Arbetet har utförts på ABB i Ludvika med avsikt att förbättra revisionsprocessenför kontroll och skydd. En revision är en ändring på ett godkänt och klarmarkeratobjekt. Då objektet i fråga redan kan vara levererat till kund och man behöver göraen ändring krävs en strukturerad process för att utföra denna ändring. Processen föratt göra detta är i dagsläget komplicerad och kräver en hel del administrativt arbete.Processen använder sig utav ett antal program för lagring och databaser så som,Lotus Notes, HiDraw Studio, och HiDra32.Avdelningen för kontroll och skydd är i fasen att övergå till ett annat elCADsystem, Engineering Base. Detta är också en av anledningarna att man önskar en nyprocess för revisionshantering.Arbetet bestod till en början av inlärning av den dåvarande processen. På detta viskunde flaskhalsar identifieras och det konstaterades var i processen fokus börläggas. Samtidigt som den gamla processen gicks igenom gavs introduktioner i detnya elCAD systemet.Målet med arbetet var att färdigställa och testa en ny process men vissa förseningarfrån Aucotec som är Engineering Base utvecklare, gjorde att tidsbrist blev ettfaktum och ett förslag till process fick bli examensarbetets slutmål.

    Download full text (pdf)
    RO hantering på ABB, TPE
  • 309. León de la Barra, B. A.
    et al.
    Jin, L. H.
    Kim, Y.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Identification of First-Order Time-Delay Systems using Two Different Pulse Inputs2008Conference paper (Refereed)
  • 310. León de la Barra, B. A.
    et al.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Identification of under-damped second-order systems using finite duration rectangular pulse inputs2007Conference paper (Refereed)
  • 311. Lim, Woei Chet
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wainwright, John
    Asymptotic silence-breaking singularities2006In: Class. Quantum Grav. 23 (2006) 2607-2630Article in journal (Refereed)
    Abstract [en]

    We discuss three complementary aspects of scalar curvature singularities: asymptotic causal properties, asymptotic Ricci and Weyl curvature, and asymptotic spatial properties. We divide scalar curvature singularities into two classes: so-called asymptotically silent singularities and non-generic singularities that break asymptotic silence. The emphasis in this paper is on the latter class which have not been previously discussed. We illustrate the above aspects and concepts by describing the singularities of a number of representative explicit perfect fluid solutions

  • 312. Lim, Woei Chet
    et al.
    van Elst, Henk
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Wainwright, John
    Asymptotic isotropization in inhomogeneous cosmology2004In: Phys.Rev. D69 (2004) 103507Article in journal (Refereed)
    Abstract [en]

    In this paper we investigate asymptotic isotropization. We derive the asymptotic dynamics of spatially inhomogeneous cosmological models with a perfect fluid matter source and a positive cosmological constant near the de Sitter equilibrium state at late times, and near the flat FL equilibrium state at early times. Our results show that there exists an open set of solutions approaching the de Sitter state at late times, consistent with the cosmic no-hair conjecture. On the other hand, solutions that approach the flat FL state at early times are special and admit a so-called isotropic initial singularity. For both classes of models the asymptotic expansion of the line element contains an arbitrary spatial metric at leading order, indicating asymptotic spatial inhomogeneity. We show, however, that in the asymptotic regimes this spatial inhomogeneity is significant only at super-horizon scales

  • 313.
    Lindkvist, Linus
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hagberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Transienta strömmar i HVDC-Light2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Download full text (pdf)
    Transienta strömmar i HVDC-Light
  • 314. Löhmus, R.
    et al.
    Erts, D.
    Löhmus, A.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Jompol, Y.
    Olin, H.
    STM and AFM instrumentation combined with transmission electron microscope2001In: Physics of Low-dimensional structuresArticle in journal (Refereed)
  • 315.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Studies of the electronic band structure of three Cd-compound II-VI semiconductors1987Doctoral thesis, monograph (Other academic)
  • 316.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Flodström, S.A.
    Experimental surface electronic band structure of the (1010) surfaces of CdS and CdSe1988In: Phys. Rev. B 38, 6137 (1988)Article in journal (Refereed)
  • 317.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Flodström, S.A.
    Valence- and conduction-band electronic structure of wurtzite CdSe1987In: Phys. Rev. B 35,2556 (1987)Article in journal (Refereed)
  • 318.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Flodström, S.A.
    Valence band structure and final states in photoemission from (1120) surfaces of CdS and CdSe1988In: Phys. Rev. B 38, 1285 (1988)Article in journal (Refereed)
  • 319.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Flodström, S.A.
    Mårtensson, P.
    Nicholls, J.M.
    Karlsson, U.O.
    Engelhardt, R.
    Koch, E.E.
    The electronic structure of wurtzite CdS studied using angle-resolved u.-v. photoelectron spectroscopy1985In: Solid State Commun. 55,643 (1985)Article in journal (Refereed)
  • 320.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Flodström, S.A.
    Persson, P.E.S.
    Valence band and surface electronic structure of CdTe1988In: Phys. Rev. B 38, 5384 (1988)Article in journal (Refereed)
  • 321.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Karlsson, U.O.
    Straub, D.
    Flodström, S.A.
    Himpsel, F.J.
    Angle-resolved inverse photoelectron spectroscopy studies of CdTe(110), CdS(1120) and CdSe(1120)1987In: Phys. Rev. B 36,6566 (1987)Article in journal (Refereed)
  • 322.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Neuhold, G.
    Horn, K.
    Evans, D.A.
    Electronic band structure of cubic CdSe determined by angle-resolved photoemission: Cd 4d and valence-level states1998In: Phys. Rev. B57, 8945 (1998)Article in journal (Refereed)
  • 323.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Destabilization of the Si(111) -bonded chain structure upon Cs adsorbtion1989In: Phys. Rev. B 39, 10456 (1989)Article in journal (Refereed)
  • 324.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Development of the surface electronic structure of K and Cs overlayers on Si(111)7x71990In: Phys. Rev. B 41, 12071 (1990)Article in journal (Refereed)
  • 325.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Filled and empty surface electronic states observed on GaAs(110)1x1-K1989In: Phys. Rev. B 40, 5864 (1989)Article in journal (Refereed)
  • 326.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Inverse and direct photoemission from alkali/semiconductor interfaces1990In: Vacuum 41, 757 (1990)Article in journal (Refereed)
  • 327.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Surface electronic structure of sub-monolayer to full-monolayer coverages of alkali metals on GaAs(110) : K and Cs1989In: Phys. Rev. B 40, 7814 (1989)Article in journal (Refereed)
  • 328.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Reihl, B.
    Persson, P.E.S.
    Empty surface electronic bands on CdTe(110)1990In: Surf. Sci. Lett. 233, L233 (1990)Article in journal (Refereed)
  • 329.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Wiklund, S.
    Interface formation of Bi on ceramic ZnO : A simple model varistor grainboundary1994In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 76, p. 7405-7409Article in journal (Refereed)
  • 330.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Wiklund, S.
    Dudde, R.
    Reihl, B.
    Adsorption of Cs on Si(111)7x7 : studies of photoemission from surface states and core levels1991In: Phys. Rev. B 44, 5657 (1991)Article in journal (Refereed)
  • 331.
    Magnusson, Kjell
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Wiklund, S.
    Dudde, R.
    Reihl, B.
    Interface formation of alkali metals on Si(111) surfaces1992In: Mol. Phys. 76, 909 (1992)Article in journal (Refereed)
  • 332.
    Magnusson, Sven
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bladh, Henrik
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Framtagning av reglerparametrar i badvattenreningsanläggningar2012Independent thesis Basic level (university diploma), 15 credits / 22,5 HE creditsStudent thesis
    Download full text (pdf)
    fulltext
  • 333. Mahata, K.
    et al.
    Mousavi, S.
    Söderström, T.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Valdek, U.
    Hillström, L.
    On the use of flexural wave propagation experiments for identification of complex modulus2003In: IEEE Transactions on Control Systems Technology, ISSN 1063-6536, E-ISSN 1558-0865, Vol. 11, no 6, p. 863-874Article in journal (Refereed)
    Abstract [en]

    In this paper, we investigate the nonparametric estimation of the frequency dependent complex modulus of a viscoelastic material. The strains due to flexural wave propagation in a bar specimen are registered at different cross sections. The time domain data is transformed into frequency domain using discrete Fourier transform and a nonlinear least squares algorithm is then employed to estimate the complex modulus at each frequency. Inherent numerical problems due to associated ill-conditioned matrices are treated with special care. An analysis of the quality of the nonlinear least squares estimate is also carried out. The validity of the theoretical results are confirmed by numerical studies and experimental tests

  • 334. Mahata, K.
    et al.
    Söderström, T.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hillström, L.
    Mousavi, S.
    Identification of complex elastic modulus from flexural wave propagation experiments2002Conference paper (Refereed)
  • 335. Mahata, K.
    et al.
    Söderström, T.
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Hillström, L.
    Mousavi, S.
    On the use of flexural wave propagation experiments for identification of complex modulus2001Report (Other academic)
  • 336. Mark Heinzle, J.
    et al.
    D. Rendall, Alan
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Theory of Newtonian self-gravitating stationary spherically symmetric systems2006In: Math. Proc. Camb. Phil. Soc. 140 (2006) 177-192Article in journal (Refereed)
    Abstract [en]

    We investigate spherically symmetric equilibrium states of the Vlasov-Poisson system, relevant in galactic dynamics. We recast the equations into a regular three-dimensional system of autonomous first order ordinary differential equations on a region with compact closure.Based on a dynamical systems analysis we derive theorems that guarantee that the steady state solutions have finite mass and compact support

  • 337. Mark Heinzle, J.
    et al.
    Rohr, N.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Matter and dynamics in closed cosmologies2005In: Phys.Rev. D71 (2005) 083506Article in journal (Refereed)
    Abstract [en]

    To systematically analyze the dynamical implications of the matter content in cosmology, we generalize earlier dynamical systems approaches so that perfect fluids with a general barotropic equation of state can be treated. We focus on locally rotationally symmetric Bianchi type IX and Kantowski-Sachs orthogonal perfect fluid models, since such models exhibit a particularly rich dynamical structure and also illustrate typical features of more general cases. For these models, we recast Einstein's field equations into a regular system on a compact state space, which is the basis for our analysis. We prove that models expand from a singularity and recollapse to a singularity when the perfect fluid satisfies the strong energy condition. When the matter source admits Einstein's static model, we present a comprehensive dynamical description, which includes asymptotic behavior, of models in the neighborhood of the Einstein model; these results make earlier claims about ``homoclinic phenomena and chaos'' highly questionable. We also discuss aspects of the global asymptotic dynamics, in particular, we give criteria for the collapse to a singularity, and we describe when models expand forever to a state of infinite dilution; possible initial and final states are analyzed. Numerical investigations complement the analytical results

  • 338. Mark Heinzle, J.
    et al.
    Rohr, N.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Spherically symmetric relativistic stellar structures2003In: Class.Quant.Grav. 20 (2003) 4567-4586Article in journal (Refereed)
    Abstract [en]

    We investigate relativistic spherically symmetric static perfect fluid models in the framework of the theory of dynamical systems. The field equations are recast into a regular dynamical system on a 3-dimensional compact state space, thereby avoiding the non-regularity problems associated with the Tolman-Oppenheimer-Volkoff equation. The global picture of the solution space thus obtained is used to derive qualitative features and to prove theorems about mass-radius properties. The perfect fluids we discuss are described by barotropic equations of state that are asymptotically polytropic at low pressures and, for certain applications, asymptotically linear at high pressures. We employ dimensionless variables that are asymptotically homology invariant in the low pressure regime, and thus we generalize standard work on Newtonian polytropes to a relativistic setting and to a much larger class of equations of state. Our dynamical systems framework is particularly suited for numerical computations, as illustrated by several numerical examples, e.g., the ideal neutron gas and examples that involve phase transitions

  • 339. Mark Heinzle, J.
    et al.
    Röhr, N.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Homoclinic chaos and energy condition violation2006In: Phys. Rev. D74 (2006) 061502Article in journal (Refereed)
    Abstract [en]

    In this letter we discuss the connection between so-called homoclinic chaos and the violation of energy conditions in locally rotationally symmetric Bianchi type IX models, where the matter is assumed to be non-tilted dust and a positive cosmological constant. We show that homoclinic chaos in these models is an artifact of unphysical assumptions: it requires that there exist solutions with positive matter energy density $\rho>0$ that evolve through the singularity and beyond as solutions with negative matter energy density $\rho<0$. Homoclinic chaos is absent when it is assumed that the dust particles always retain their positive mass.In addition, we discuss more general models: for solutions that are not locally rotionally symmetric we demonstrate that the construction of extensions through the singularity, which is required for homoclinic chaos, is not possible in general

  • 340. Mark Heinzle, J.
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Dynamics of the spatially homogeneous Bianchi type I Einstein-Vlasov equations2006In: Class. Quantum Grav. 23 (2006) 3463-3490Article in journal (Refereed)
    Abstract [en]

    We investigate the dynamics of spatially homogeneous solutions of the Einstein-Vlasov equations with Bianchi type I symmetry by using dynamical systems methods. All models are forever expanding and isotropize toward the future; toward the past there exists a singularity. We identify and describe all possible past asymptotic states; in particular, on the past attractor set we establish the existence of a heteroclinic network, which is a new type of feature in general relativity. This illustrates among other things that Vlasov matter can lead to quite different dynamics of cosmological models as compared to perfect fluids

  • 341. Mark Heinzle, J.
    et al.
    Uggla, Claes
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Newtonian Stellar Models2003In: Annals Phys. 308 (2003) 18-61Article in journal (Refereed)
    Abstract [en]

    We investigate static spherically symmetric perfect fluid models in Newtonian gravity for barotropic equations of state that are asymptotically polytropic at low and high pressures. This is done by casting the equations into a 3-dimensional regular dynamical system with bounded dependent variables. The low and high central pressure limits correspond to two 2-dimensional boundary subsets, described by homology invariant equations for exact polytropes. Thus the formulation naturally places work about polytropes in a more general context. The introduced framework yields a visual aid for obtaining qualitative information about the solution space and is also suitable for numerical investigations. Last, but not least, it makes a host of mathematical tools from dynamical systems theory available. This allows us to prove a number of theorems about the relationship between the equation of state and properties concerning total masses and radii

  • 342.
    Modig, Niklas
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Study of Different Concepts of Harmonic Filters Variable in Frequency Range2012Independent thesis Basic level (degree of Bachelor), 15 credits / 22,5 HE creditsStudent thesis
    Abstract [en]

    Many harmonics are generated in the HVDC converters during operation. To avoid the harmonics to

    reach the AC network, AC filters are installed at the converter station. A filter bank does usually

    consist of band pass filters for the major harmonics and high pass filters for the higher order harmonics.

    The band pass filters are designed to work as a short circuit for one specific harmonic current.

    If the filter parameters such as fundamental frequency or capacitance in the capacitor banks start to

    alter, the filter performance will decrease.

    By being able to compensate the tuning frequency of the filter it is possible to always keep a good filter

    performance. Variable filters can be designed by either controlling the capacitance or the inductance.

    The capacitance can be controlled by connecting or disconnecting tuning capacitors. The inductance

    can be altered by using adjustable reactors with tap changers.

    Variable AC filters can be designed with a narrower bandwidth and higher Q-factor (quality factor),

    compared to a passive filter. A higher Q-factor will provide lower the active power losses.

    A smart design of the variable filter may decrease the footprint of the filter. The decrease will lead to

    smaller filter yards and lower costs for prepared surface.

    A smart control system must be used to calculate the appropriate filter characteristics. The control

    system must be applied with special features to make the filter run as smooth as possible. Some

    features are synchronized connection, hysteresis and detection of filter failure.

    Variable AC filters are a requirement for HVDC stations including CCC (Capacitor Commutated

    Converter) compensation. In connection with CCC the band pass filter will earn a very narrow

    bandwidth. If the AC filters is not variable, the performance will decrease a lot during frequency

    deviations.

    The conclusion is that a variable filter will increase the filter performance when the frequency is

    deviating and the ambient temperature is altering the filter capacitance. Installation of variable filters

    offers smaller footprints, lower losses, better performance and lower costs.

  • 343.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Conjugated Polymer Blends: Linking Film Morphology to Performance of Light Emitting Diodes and Photodiodes2002In: J. Phys.: Condens. Matter 14, 47 (2002) p. 12235-12260Article in journal (Refereed)
  • 344.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Polymer solar cells – Visualising spontaneous organisation in solution-based thin films of Polymer:fullerene blends2011In: Soft and hard materials: A symposium on surface and materials chemistry / [ed] Swedish Chemical Society, division for surface and materials chemistry, 2011Conference paper (Refereed)
    Abstract [en]

    The performance and recent improvements of polymer-based solar cells can be traced back

    to two main factors: the chemical design of new conjugated polymers and the control and

    improved understanding of morphology in these solution-processed thin films. When a thin

    film is prepared from a blend of a conjugated polymer and the fullerene-based material,

    PCBM, demixing determines the final nanostructure, which in turn is influenced by the

    polymer-fullerene interactions, the molecules’ tendency to self-organise, and the kinetics of

    the film formation. During spincoating, characterized of rapid solvent evaporation, the

    kinetics of nucleation and of two-phase separation compete. The resulting film morphology

    is important for the performance of photovoltaic devices, because, first of all, excitons need

    to diffuse to the donor/acceptor interface to separate into mobile charges, and, secondly,

    these mobile charges need to travel to the electrodes. Characterization of the structure,

    composition and molecular orientation at these interfaces and in the thin film has been one

    major challenge, because of the critical requirements of chemical contrast combined with

    lateral or depth resolution. We have used a combination of Atomic Force Microscopy

    (AFM), dynamic Secondary Ion Mass Spectrometry (d-SIMS), Near-Edge Absorption Fine

    Structure (NEXAFS) spectroscopy, and recently Neutron Reflectometry (NR), to probe the

    surface and bulk composition of polymer:fullerene blends. Differences in composition

    between surface and sub-surface are observed, and form strong evidence for vertical phase

    separation.

     

  • 345.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Spontaneous Organisation in Films of Polymer:Fullerene Blends2011Conference paper (Refereed)
  • 346.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Materials Science. Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Vertical Phase Separation in Polymer:Fullerene Films for Photovoltaics2012In: Hybrid and Organics Photovoltaics Conference 2012: Uppsala, Sweden, 6th to 9th May 2012 / [ed] Anders Hagfeldt, Castelló, Spain: Society for Nanomolecular Photovoltaics (SEFIN) , 2012, p. 53-53Conference paper (Refereed)
  • 347.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Björström Svanström, Cecilia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Magnusson, Kjell
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Rysz, J
    Bernasik, A
    Budkowski, A
    Zhang, F
    Benson-Smith, J.J
    Inganäs, O
    Andersson, M.R
    Nelson, J
    Device performance of APFO-3/PCBM solar cells with controlled morphology2009In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 21, no 43, p. 4398-4403Article in journal (Refereed)
    Abstract [en]

    Polymer/fullerene solar cells with three different device structures: A) diffuse bilayer, B) spontaneously formed multilayer, and C) vertically homogenous thin films, are fabricated. The photocurrent/voltage performance is compared and it is found that the self-stratified structure (B) yields the highest energy conversion efficiency

  • 348.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Eschle, M.K.
    Grätzel, M.
    Determination of the Energy Diagram of the Dithioketopyrrolopyrrole/SnO2:F Heterojunctions by Surface Photovoltage Spectroscopy1997In: Appl. Phys. Lett. 71, 22 (1997) p. 3305-3307Article in journal (Refereed)
  • 349.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Gal, D.
    Beier, J.
    Hodes, G.
    Cahen, D.
    Kronik, L.
    Burstein, L.
    Mishori, B.
    Shapira, Y.
    Hariskos, D.
    Chock, H.W.
    Effect of Air Annealing on the Electronic Properties of CdS/Cu(In,Ga)Se2 Solar Cells1996In: Solar Energy Mater. Solar Cells 43, 1 (1996) p. 73-78Article in journal (Refereed)
  • 350.
    Moons, Ellen
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Goossens, A.
    Savenije, TJ.
    Surface Photovoltage of Porphyrin Layers Using the Kelvin Probe Technique1997In: J. Phys. Chem. B 101, 42 (1997) p. 8492-8498Article in journal (Refereed)
45678910 301 - 350 of 699
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