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  • 3601.
    Åstrand, Max
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ventilation Performance Monitoring in Underground Mines2016Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ventilation of underground mines is a critical, complex and expensive activity. Removing pollutants from e.g. diesel equipment is important to insure a safe and operable work environment in the mine. The energy consumption of ventilation for an underground mine typically comprises around 30-50% of the total energy consumption of underground mine operation. It is therefore vital that the performance of the ventilation system can be monitored and maintained as high as possible. The goal of this project is to develop methods  and algorithms which are useful in this context. The developed methods and algorithms are tested in two real mine case studies.

  • 3602.
    Öberg, Fredrik
    et al.
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Askenfelt, Anders
    KTH, School of Computer Science and Communication (CSC), Speech, Music and Hearing, TMH, Music Acoustics.
    Acoustical and perceptual influence of duplex stringing in grand pianos2012In: Journal of the Acoustical Society of America, ISSN 0001-4966, E-ISSN 1520-8524, Vol. 131, no 1, p. 856-871Article in journal (Refereed)
    Abstract [en]

    This study investigates the acoustical and perceptual influence of the string parts outside the speaking length in grand pianos (front and rear duplex strings). Acoustical measurements on a grand piano in concert condition were conducted, measuring the fundamental frequencies of all main and duplex strings in the four octaves D4-C8. Considerable deviations from the nominal harmonic relations between the rear duplex and main string frequencies, as described by the manufacturer in a patent, were observed. Generally the rear duplex strings were tuned higher than the nominal harmonic relations with average and median deviations approaching _50 cent. Single keys reached +190 and -100 cent. The spread in deviation from harmonic relations within trichords was also substantial with average and median values around 25 cent, occasionally reaching 60 cent. Contributions from both front and rear duplex strings were observed in the bridge motion and sound. The audibility of the duplex strings was studied in an ABX listening test. Complete dampening of the front duplex was clearly perceptible both for an experiment group consisting of musicians and a control group with naive subjects. The contribution from the rear duplex could also be perceived, but less pronounced.

  • 3603.
    Öberg, Sven
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Adjizian, Jean-Joseph
    Department of Chemistry, University of Sussex, Falmer, Brighton , Nanoscopic Physics (NAPS), Université catholique de Louvain.
    Erbahar, D.
    Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Rio, J.
    Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Humbert, Bernard
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Dossot, Manuel
    Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, Nancy Université, Laboratoire de Chimie Physique et Microbiologie pour l'Environnement, UMR 7564, CNRS–University of Lorraine.
    Soldatov, Alexander
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Lefrant, S.
    Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Mevellec, J-Y
    Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Briddon, Patrick R.
    Department of Physics, University of Newcastle, School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne, School of Natural Science, University of Newcastle upon Tyne, Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford, School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne.
    Ewels, Christopher P.
    Department of Physics, University of Exeter, CPES, University of Sussex, Falmer, Brighton, Université de Nantes, Institut des Mat´eriaux Jean Rouxel (IMN), Universit´e de Nantes, Centre national de la recherche scientifique (CNRS).
    Effect of functionalization and charging on resonance energy and radial breathing modes of metallic carbon nanotubes2016In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 93, no 4, article id 45408Article in journal (Refereed)
    Abstract [en]

    While changes in resonant Raman scattering measurements are commonly used to measure the effect of chemical functionalization on single-walled carbon nanotubes, the precise effects of functionalization on these spectra have yet to be clearly identified. In this density functional theory study, we explore the effects of functionalization on both the nanotube resonance energy and frequency shifts in radial breathing mode. Charge transfer effects cause a shift in the first Van Hove singularity spacings, and hence resonance excitation energy, and lead to a decrease in the radial breathing mode frequency, notably when the Fermi level decreases. By varying stochastically the effective mass of carbon atoms in the tube, we simulate the mass effect of functionalization on breathing mode frequency. Finally, full density functional calculations are performed for different nanotubes with varying functional group distribution and concentration using fluorination and hydrogenation, allowing us to determine overall effect on radial breathing mode and charge transfer. The results concur well with experiment, and we discuss the importance when using Raman spectroscopy to interpret experimental functionalization treatments

  • 3604.
    Ödén, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Proton plan evaluation: a framework accounting for treatment uncertainties and variable relative biological effectiveness2017Licentiate thesis, comprehensive summary (Other academic)
  • 3605.
    Ögren, Magnus
    Dept. of Mathematics, Technical University of Denmark, Kongens Lyngby, Denmark.
    ESGI-88 (European Study Group with Industry) workshop on industrial mathematics: Report2012Report (Other academic)
  • 3606.
    Ögren, Magnus
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Klassisk mekanik vs kvantmekanik2010In: Forskning, ISSN 1654-8876, no 3-4, p. 50-54Article, review/survey (Other (popular science, discussion, etc.))
  • 3607.
    Ögren, Magnus
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Lärarhandledning [Teacher's manual] till: Kvantvärldens fenomen: teori och begrepp2006Book (Other academic)
  • 3608.
    Ögren, Magnus
    Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Problem med lösningar till kvantmekanik: fördjupningskurs2006Book (Other academic)
  • 3609.
    Ögren, Magnus
    et al.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Bengtsson, Ragnar
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Vektoranalys: övningar2009Book (Other academic)
  • 3610.
    Ögren, Magnus
    et al.
    ARC Centre of Excellence for Quantum-Atom Optics, School of Mathematics and Physics, University of Queensland, Brisbane, Australia.
    Carlsson, M.
    Mathematics Department, Purdue University, West Lafayette IN, United States.
    An exact lower energy bound for the infinite square well potential2011In: European journal of physics, ISSN 0143-0807, E-ISSN 1361-6404, Vol. 32, no 2, p. L3-L6Article in journal (Refereed)
    Abstract [en]

    We give a lower bound for the energy of a quantum particle in the infinite square well. We show that the bound is exact and identify the well-known element that fulfils the equality. Our approach is not directly dependent on the Schrödinger equation and illustrates an example where the wavefunction is obtained directly by energy minimization. The derivation presented can serve as an example of a variational method in an undergraduate level university course in quantum mechanics.

  • 3611.
    Ögren, Magnus
    et al.
    Department of Mathematics, Technical University of Denmark, Kgs. Lyngby, Denmark.
    Carlsson, M.
    Center for Mathematical Sciences, Lund University, Lund, Sweden.
    On the dynamics of the Fermi-Bose model2013In: Journal of Physics A: Mathematical and Theoretical, ISSN 1751-8113, E-ISSN 1751-8121, Vol. 46, no 1, article id 015005Article in journal (Refereed)
    Abstract [en]

    We consider the exponential matrix representing the dynamics of the Fermi-Bose model in an undepleted bosonic field approximation. A recent application of this model is molecular dimers dissociating into its atomic compounds. The problem is solved in D spatial dimensions by dividing the system matrix into blocks with generalizations of Hankel matrices, here referred to as D-block-Hankel matrices. The method is practically useful for treating large systems, i.e. dense computational grids or higher spatial dimensions, either on a single standard computer or a cluster. In particular the results can be used for studies of three-dimensional physical systems of arbitrary geometry. We illustrate the generality of our approach by giving numerical results for the dynamics of Glauber type atomic pair correlation functions for a non-isotropic three-dimensional harmonically trapped molecular Bose-Einstein condensate.

  • 3612.
    Ögren, Magnus
    et al.
    Mathematical Physics, Lund Institute of Technology, Lund, Sweden.
    Heiselberg, H.
    University of Southern Denmark, Odense, Denmark.
    Supershell structures and pairing in ultracold trapped Fermi gases2007In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 76, no 2, article id 021601Article in journal (Refereed)
    Abstract [en]

    We calculate level densities and pairing gaps for an ultracold dilute gas of fermionic atoms in harmonic traps under the influence of mean field and anharmonic quartic trap potentials. Supershell nodes, which were found in Hartree-Fock calculations, are calculated analytically within periodic orbit theory as well as from WKB calculations. For attractive interactions, the underlying level densities are crucial for pairing and supershell structures in gaps are predicted.

  • 3613.
    Ögren, Magnus
    et al.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Yu, Y.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Åberg, S.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Reimann, S. M.
    Division of Mathematical Physics, LTH, Lund University, Lund, Sweden.
    Brack, M.
    Institut für Theoretische Physik, Universität Regensburg, Regensburg, Germany.
    Super-shell structure in harmonically trapped fermionic gases and its semi-classical interpretation2006In: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, no T125, p. 37-40Article in journal (Refereed)
    Abstract [en]

    It was recently shown in self-consistent Hartree–Fock calculations that a harmonically trapped dilute gas of fermionic atoms with a repulsive two-body interaction exhibits a pronounced super-shell structure: the shell fillings due to the spherical harmonic trapping potential are modulated by a beat mode. This changes the 'magic numbers' occurring between the beat nodes by half a period. The length and amplitude of the beating mode depends on the strength of the interaction. We give a qualitative interpretation of the beat structure in terms of a semi-classical trace formula that uniformly describes the symmetry breaking U(3) → SO(3) in a three-dimensional harmonic oscillator potential perturbed by an anharmonic term ∝ r 4 with arbitrary strength. We show that at low Fermi energies (or particle numbers), the beating gross-shell structure of this system is dominated solely by the twofold degenerate circular and (diametrically) pendulating orbits.

  • 3614.
    Öhlund, Olof
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Larsson, Conny
    Uppsala University, Disciplinary Domain of Science and Technology, Earth Sciences, Department of Earth Sciences, LUVAL.
    Wind turbine sound propagation in the atmospheric boundary layer – comparison between measurements and models2014Conference paper (Other academic)
    Abstract [en]

    Continuous acoustic measurements were taken for two years at two different wind turbine sites in Sweden. The sites were covered by forest; one site is relatively flat while the other has shifting terrain. Meteorological parameters from the ground to above 120 m height were measured in parallel with the acoustics. The long measurement time capture all different sound propagation conditions that occur due to seasonal and daily variations in the weather. Strict criteria were developed to avoid disturbances from ambient noise. The results show that meteorological effects on wind turbine sound propagation increase with distance and start to be important at distances somewhere between 400 – 1000 m. Variations of expected values between 6 - 14 dBA at the immission point are found depending on ground conditions and refraction. The effects are seen for all 1/3-octave bands from 63 Hz – 1000 Hz.

    A comparison between the wind turbine sound measurements and the Nord2000, ISO 9613-2 and Swedish Environmental Protection Agency sound propagation models reveals that models underestimates the highest WT sound levels. This shows the importance of including meteorological effects and terrain shape in models, to give accurate predictions.  

  • 3615.
    Öhman, L. O.
    et al.
    Umeå universitet.
    Ganemi, B.
    Kungliga tekniska högskolan, KTH.
    Björnbom, E.
    Kungliga tekniska högskolan, KTH.
    Rahkamaa, K.
    Åbo Akademi.
    Keiski, R. L.
    Uleåborg universitet.
    Paul, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Catalyst preparation through ion-exchange of zeolite Cu-, Ni-, Pd-, CuNi- and CuPd-ZSM-52002In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 73, no 2-3, p. 263-267Article in journal (Refereed)
    Abstract [en]

    Ion-exchanged zeolite ZSM-5 is the best known catalyst for direct NOx decomposition and a viable candidate for NOx reduction with methane. The preparation is crucial for the efficiency of the conversion and this paper describes the ion-exchange, with Cu2+, Ni2+ or Pd2+, and the dual exchange, with Cu2+/Ni2+ or Cu2+/Pd2+, under appropriate pH and ion concentrations for maximum dispersion.

  • 3616.
    Öhman, L.O.
    et al.
    Umeå universitet.
    Paul, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Materials aspects of titanium-doped aluminas: 14%Ti/γ-Al2O3/Cu and sulfided Al2O3-TiO2/NiMo2002In: Materials Chemistry and Physics, ISSN 0254-0584, E-ISSN 1879-3312, Vol. 73, no 2-3, p. 242-251Article in journal (Refereed)
    Abstract [en]

    Materials aspects of titanium-doped alumina catalysts are discussed in light of a partly new synthesis route, ion exchange reactions and sulfidation. Starting with a solution of the isopropoxides of aluminum and titanium, we aimed at an Al:Ti ratio of 6:1, which corresponds to the maximum acidity of the final product. Transmission electron micrographs showed that the synthesis gave a product of nearly monodisperse, rectangular particles and X-ray diffractograms revealed an amorphous to nano-crystalline structure reminiscent of γ-Al2O3. The Brunauer-Emmet-Teller area was 340 m2 g-1 and the H+ titration found 3 acidic sites nm-2. These numbers indicate that the titanium modification may fourfold increase the ion exchange capacity of a regular alumina. The importance of titanium modification for catalysis is discussed in connection with selective catalytic reduction with hydrocarbon reactions over Cu/14%Ti-Al2O3 and hydrogenation of 1-Me-naphthalene over sulfided NiMo/Al2O3-TiO2. The Ti4+ ions in the alumina lattice are almost irreducible, but infrared spectra suggested that these ions act as dispersion agents not only for adsorbed Cu2+ ions, but also for a supported phase of sulfided NiMo. Finally, we show that a simple weight control can be used to monitor the sulfidation and to indicate if the synthesis has produced a separate, reducible titania phase.

  • 3617.
    Öhman, Nikanor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Simulation of LiDAR data for forestry applications2018Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In forestry it is important to have accurate information about the forest. LiDAR (laser scanning) can be used to scan vast areas of forest and from the data extract information about the trees. The purpose of this thesis is to develop a simulator for LiDAR data. The simulator will be tested on a method for tree localization (Holmgren and Lindberg 2013) to see how parameters like tree density and laser frequency effects the accuracy of the localization. First a simulator which uses simple shaped trees (in the shape of cones) is written. Later on a tree model based on real laser data is created by the use of histogram density estimation. Ray-tracing is used to simulate the LiDAR data which the trees give rise to. This is done by following each ray of laser and see where it is reflected. The tree localization method is tested on the data and we report the following findings: 1: The percentage of correctly located trees decreases with increasing tree density. 2: Larger trees yields an increase in false trees found by the localization method. 3: Higher laser pulse density decreases the number of false trees. 4: The minimum radius at which the localization method start fitting ellipsoids greatly effects the number of false trees. Smaller radius yield more false trees.

  • 3618.
    Öhrman, Jakob
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evaluation of a CFD method for estimating aerodynamic loads on external stores on JAS 39 Gripen2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Loads determination for external stores on fighter aircraft is an important task for manufacturers in ensuring the safe operation of their aircraft. Due to the large number of possible store combinations, wind tunnel tests – the primary approach to obtaining loads data – cannot be performed for all configurations. Instead, supplementary techniques to estimating loads are necessary. One approach is to use information from another store and adapt it, using so-called scaling methods, to the non-tested store.

    In this thesis, a scaling method combining the results of computational fluid dynamics (CFD) simulations, for both a non-tested and a reference store, with existing wind tunnel data for the reference store, is thoroughly examined for a number of different stores, angles of attack, sideslip angles and Mach numbers. The performance of the proposed scaling method is assessed in relation to currently used scaling methods, using non-parametric and multivariate statistics.

    The results show no definitive improvement in performance for the proposed scaling method over the current methods. Although the proposed method is slightly more conservative, considerable variability in the estimates and an increased time consumption for scaling leads the author to advise against using the proposed method for scaling aerodynamic loads on external stores.

  • 3619.
    Örlü, Ramis
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, Linné Flow Center, FLOW.
    Talamelli, A.
    Oberlack, M.
    Peinke, J.
    Preface2017In: Springer Proceedings in Physics, Springer Science+Business Media B.V., 2017, Vol. 196, p. v-viConference paper (Refereed)
  • 3620.
    Örn, Markus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Towards Better Alternator Efficiency2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The requirements on vehicle industry are constantly getting stricter, especially when it comes to emissions. At the same time cars, trucks and buses are needed for our way of living. This have forced companies to be as ecient as possible in their way of using fossil fuels for travelling and transport. To increase the eciency companies investigate all possible fuel savings to decrease their carbon footprint as much as possible. One area of savings that is not that obvious to many people is the alternator. Several percent of the total energy used by a vehicle are needed to operate the alternator. With a typical alternator eciency of 70% considerable savings can be achieved.

    This thesis that concern alternator eciency was carried out at Scania in Södertälje, Sweden. The goal of the thesis is to construct a mathematical model of an alternator. The model is supposed to consider all losses in the alternator and together with the output power give an eciency model of the alternator at different speeds and loads. A great part of the project has been dealing with the magnetic losses. The magnetic losses have been modeled as an equivalent circuit with the load angle as a central piece. The equivalent circuit is built up by the fact that the alternator used in the vehicles is a salient pole alternator. The equivalent circuit describes a voltage equation where the voltage drop over the magnetic inductance is described. From that relations between the signals in the alternator and output signals can be written.

    The alternator model is then used together with data recorded from different buses all over the world, this to be able to investigate how the alternator contributes to the fuel consump- tion depending on the way that the buses are driven.

    The result of this thesis is a mathematical model that describes the losses in the alternator for different load cases and speeds. 

  • 3621.
    Öster, Michael
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics . Linköping University, The Institute of Technology.
    Stability and Mobility of Localized and Extended Excitations in Nonlinear Schrödinger Models2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis is mainly concerned with the properties of some discrete nonlinear Schrödinger equations. These naturally arise in many different physical contexts as the limiting form of general dynamical lattice equations that incorporate nonlinearity and coupling. Interest is focused on theoretical models of coupled optical waveguides constructed from materials with a nonlinear index of refraction. In arrays of waveguides the overlap of the evanescent electric field of the modes in neighbouring waveguides provides a coupling and the nonlinearity of the material provides a mechanism to halt the discrete diffraction that otherwise would spread localized energy across the array. In particular, waveguide structures where also a nonlinear coupling is taken into account are studied. It is noted that the equation for the evolution of the complex amplitudes of the electric field along an array of waveguides also can be used to describe the dynamics of Bose-Einstein condensates trapped in a periodic optical potential. Possible excitations in arrays in both one and two dimensions are considered, with emphasis on the effects of the nonlinear coupling.

    Localized excitations are considered from the viewpoint of the theory of discrete breathers, or intrinsic localized modes, i.e., solutions of the dynamical equations that are periodic in time and have a spatial localization. The general theory of such solutions, that appear under very general circumstances in nonlinear lattice equations, is reviewed. In an array of waveguides this means that light can propagate along the array confined essentially to one or a few waveguides. In general a distinction is made between excitations that are centred on a waveguide, or site in the lattice, and excitations that are centred inbetween waveguides. Usually only the former give stable propagation. When the localized beam can be displaced to neighbouring waveguides the array can operate as an optical switch. With the inclusion of nonlinear coupling between the sites, as in the model derived in this thesis, the stability of the site-centred and bond-centred solutions can be exchanged. It is shown how this leads to the existence of highly localized mobile solutions that can propagate transversely in the one-dimensional array of waveguides. The inversion of stability of stationary solutions occurs also in the two-dimensional array, but in this setting it fails to give good mobility of localized excitations. The reason for this is also explained.

    In a two-dimensional lattice a discrete breather can have the form of a vortex. This means that the phase of the complex amplitude will vary on a contour around the excitation, such that the phase is increased by 2πS, where S is the topological charge, on the completion of one turn. Some ring-like vortex excitations are considered and in particular a stable vortex with S=2 is found. It is also noted that the effect of charge flipping, i.e., when the topological charge periodically changes between -S and S, is connected to the existence of quasiperiodic solutions.

    The nonlinear coupling of the waveguide model will also give rise to some more exotic and novel properties of localized solutions, e.g., discrete breathers with a nontrivial phase. When the linear coupling and the nonlinear coupling have opposite signs, there can be a decoupling in the lattice that allows for compact solutions. These localized excitations will have no decaying tail. Of interest is also the flexibility in controlling the transport of power across the array when it is excited with a nonlinear plane wave. It is shown how a change of the amplitude of a plane wave can affect the magnitude and direction of power flow in the array.

    Also the continuum limit of the one-dimensional discrete waveguide model is considered with an equation incorporating both nonlocal and nonlinear dispersion. In general continuum equations the balance between nonlinearity and dispersion can lead to the formation of localized travelling waves, or solitons. With nonlinear dispersion it is seen that these solitons can be nonanalytic and have discontinuous spatial derivatives. The emergence of short-wavelength instabilities due to the simultaneous presence of nonlocal and nonlinear dispersion is also explained.

  • 3622.
    Österdahl, Emma
    Karlstad University, Faculty of Arts and Social Sciences (starting 2013), Department of Educational Studies (from 2013).
    Barns utforskande av fysikaliska fenomen på kullar: En design-baserad studie om barns utforskande av friktion.2019Independent thesis Basic level (professional degree), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The aim of the study is to provide knowledge about how children explore, understand and reason about the physical phenomenon of friction. This study have been based on the younger children’s exploring. The method of the study has been observation in order to get as close to the environment that’s being investigated and to bring attention to the younger children’s actions. A nonparticipating observation was also used for the observer to influence the children as little as possible. The observations that have been made have taken place over two days and have been video recorded to ensure documentation of children's reasoning, body language and actions. The result shows how the children focused on overcoming the friction to get an object to slide instead of getting stuck. The participants’ interaction also emerged in the result as central to driving the exploration further. The conclusions drawn after the study is that the result can be linked to the preschool’s curriculum, which addresses the fact that the children should be given the opportunity to explore, discuss and develop understanding of physical phenomena. The study has also highlighted that hills can be used as a tool for teaching and exploring the phenomenon of friction.

  • 3623.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Chakarov, D V
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Potassium adsorption on graphite(0001)1999In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 420, no 2-3, p. 174-189Article in journal (Refereed)
    Abstract [en]

    Potassium adsorption on graphite has been studied with emphasis on the two-dimensional K adlayer below one monolayer. Data are presented for the work function versus coverage, high-resolution electron energy loss spectroscopy (HREELS) vibrational spectra of K-adlayers, low energy electron diffraction and ultraviolet photoemission spectroscopy (UPS) spectra at different coverages. The data provide information regarding the vibrational properties of the K-adlayer, the metallization of the adlayer at submonolayer coverages, and the charge transfer from the It adatoms to the graphite substrate. Analysis of the work function, HREELS, and UPS data provides a qualitatively consistent picture of the charge state of the K adatoms, where at low coverages, below a critical coverage theta(c) (theta(c) = 0.2-0.3), the K adatoms are dispersed and (partially) ionized, whereas at theta > theta(c) islands of a metallic 2 x 2 K phase develop that coexist with the dispersed K adatoms up to theta = 1. We show that it is possible to understand the variation of the work function data based on a two-phase model without invoking a depolarization mechanism of adjacent dipoles, as is normally done for alkali-metal adsorption on metal surfaces. Similarly, the intensity variation as a function of coverage of the energy loss peak at 17 meV observed in HREELS, and the photoemission peak at E-b = 0.5 eV seen in UPS can be understood from a two-phase model. A tentative explanation is presented that connects apparent discrepancies in the literature concerning the electronic structure of the K adlayer. In particular, a new assignment of the K-induced states near the Fermi level is proposed. (C) 1999 Elsevier Science B.V. All rights reserved.

  • 3624.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Kielbassa, S
    Chalmers University of Technology.
    Werdinius, C
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Reactivity of Pt/ceria and Pt/alumina planar model catalysts prepared by colloidal lithography2003In: Journal of Catalysis, ISSN 0021-9517, E-ISSN 1090-2694, Vol. 215, no 1, p. 94-107Article in journal (Refereed)
    Abstract [en]

    We report on the structure, chemical state, and catalytic activity of nanofabricated, planar Pt/ceria and Pt/alumina model catalysts prepared by colloidal lithography. Employing extended etching times, catalyst particles are fabricated that are much smaller than the size of the polystyrene colloidal particle mask. Using CO oxidation as a probe reaction, the influence of various pretreatments has been studied. We find that the H-2/O-2 pretreatment deteriorates the reactivity on Pt/alumina, which is accompanied by blocking of the high-temperature CO adsorption sites as seen by TPD. After prolonged reactions the Pt/ceria particles show pronounced restructuring, indicating a low-temperature, reaction-induced, strong metal-support interaction, where ceria is decorating the Pt particles. In contrast, after an identical reaction history the Pt/alumina particles become facetted. The nanofabrication approach allows us to attribute the structural changes on individual particles to the integrated, macroscopic catalytic response. (C) 2003 Elsevier Science (USA). All rights reserved.

  • 3625.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Pedersen, M O
    University of Aarhus, Aarhus, Denmark.
    Stensgaard, I
    University of Aarhus, Aarhus, Denmark.
    Laegsgaard, E
    University of Aarhus, Aarhus, Denmark.
    Besenbacher, F
    University of Aarhus, Aarhus, Denmark.
    Quantitative determination of adsorbate-adsorbate interactions1999In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 83, no 23, p. 4812-4815Article in journal (Refereed)
    Abstract [en]

    A new concept called configuration distribution analysis is introduced to extract quantitative information on adsorbate-adsorbate interactions from high-resolution scanning tunneling microscopy data. From atom-resolved nitrogen island configurations on an Fe(100) surface we show that the propensity to form small, compact c(2 X 2) nitrogen islands is due to a nearest neighbor repulsion and next-nearest neighbor attraction. We demonstrate the importance of including many-body terms and elastic interactions to account for the detailed description of the island distribution.

  • 3626.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Rasmussen, P B
    University of Aarhus, Aarhus, Denmark.
    Thostrup, P
    University of Aarhus, Aarhus, Denmark.
    Laegsgaard, E
    University of Aarhus, Aarhus, Denmark.
    Stensgaard, I
    University of Aarhus, Aarhus, Denmark.
    Besenbacher, F
    University of Aarhus, Aarhus, Denmark.
    Bridging the pressure gap in surface science at the atomic level: H/Cu(110)2001In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 86, no 3, p. 460-463Article in journal (Refereed)
    Abstract [en]

    The structural response of the Cu(110) surface to H-2 gas pressures ranging from 10(-13) to 1 bar is studied using a novel high-pressure scanning tunneling microscope (HP-STM). We find that at H-2 pressures larger than 2 mbar the Cu(110) surface reconstructs into the (1 X 2) "missing-row" structure. From a quantitative analysis of the pressure dependence of the surface reconstruction, we conclude that Cu(110) responds identically to hydrogen at ultrahigh vacuum conditions and at atmospheric pressures. From the HP-STM data, we extract refined values for the adsorption and desorption rate constants.

  • 3627.
    Österlund, Lars
    et al.
    Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Physics.
    Zoric, I
    Chalmers University of Technology.
    Kasemo, B
    Chalmers University of Technology.
    Dissociative sticking of O-2 on Al(111)1997In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 55, no 23, p. 15452-15455Article in journal (Refereed)
    Abstract [en]

    The dissociative sticking probability, S-0, of O-2 on Al(111) has been measured as a function of incident translational and vibrational energy. S-0 rises from approximate to 10(-2) for energies approximate to 30 meV to near unity in the range 0.6-2.0 eV, demonstrating an activated dissociation event. Vibrational excitation enhances the sticking. Surface temperature has no effect on S-0. A peculiar dependence on polar angle is observed. The results are used to discuss possible mechanisms for the recent observation [H. Brune et al. Phys. Rev. Lett. 68, 624 (1992)] of widely separated O atoms after O-2 dissociation on Al(111).

  • 3628.
    Österlund, Michael
    et al.
    Jönköping University, School of Engineering, JTH, Physics.
    Nilsson, Örjan
    Jönköping University, School of Engineering, JTH, Physics.
    Modern Technology in Physics Education1998In: SEFI WGP Seminar EMEPE98, 1998, p. 5-Conference paper (Other scientific)
  • 3629.
    Österlund, Michael
    et al.
    Jönköping University, School of Engineering, JTH, Physics.
    Nilsson, Örjan
    Jönköping University, School of Engineering, JTH, Physics.
    Projectile Motion in Real Life2000In: Proc. Physics Teaching in Engineering Education (PTEE 2000), 2000Conference paper (Other scientific)
  • 3630.
    Österlund, Michael
    et al.
    Jönköping University, School of Engineering, JTH, Physics.
    Nilsson, Örjan
    Jönköping University, School of Engineering, JTH, Physics.
    Simulering med Interactive Physics1997In: Datorn i Utbildningen, ISSN 1100-3650, no 1, p. 36-39Article in journal (Other (popular science, discussion, etc.))
  • 3631.
    Östman, Alexander
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Collision detection for trimming curves and BREPs2014Independent thesis Advanced level (degree of Master (Two Years)), 300 HE creditsStudent thesis
    Abstract [en]

    This report treats the implementation of collision detection algorithms for Boundary representations (BREPs) consisting of connected trimmed surfaces, mainly Non Uniform Rational Basis Spline (NURBS) surfaces. Using the OpenNurbs software package, complicated geometries created in CAD program Space Claim were imported to the physics engine AgX, where dynamic simulations were carried out. Collision detection algorithms for the geometry pairs BREP-line, BREP-plane and BREP-sphere have been developed and investigated. In the case of BREP-sphere collision detection, experiments have been carried out which show that BREP-shape representation exceeds trimesh-shape representation both in computational performance and in collision accuracy. The conclusion is that BREP representation has the potential to replace trimesh representation for some complex geometries with higher computational performance and more accurate simulations as a result.

  • 3632.
    Öström, Jonatan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Erratum: “Reaction rate constant for radiative association of CF+” [J. Chem. Phys. 144, 044302 (2016)]2019In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 150, no 24, article id 249901Article in journal (Refereed)
  • 3633.
    Öström, Jonatan
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Bezrukov, Dmitry S.
    Department of Chemistry, M. V. Lomonosov Moscow State University.
    Nyman, Gunnar
    Department of Chemistry and Molecular Biology, University of Gothenburg.
    Gustafsson, Magnus
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Reaction rate constant for radiative association of CF+2016In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 144, no 4, article id 44302Article in journal (Refereed)
    Abstract [en]

    Reaction rate constants and cross sections are computed for the radiative association of carbon cations (C+) and fluorine atoms (F) in their ground states. We consider reactions through the electronic transition 11Π → X1Σ+ and rovibrational transitions on the X1Σ+ and a3Π potentials. Semiclassical and classical methods are used for the direct contribution and Breit–Wigner theory for the resonance contribution. Quantum mechanical perturbation theory is used for comparison. A modified formulation of the classical method applicable to permanent dipoles of unequally charged reactants is implemented. The total rate constant is fitted to the Arrhenius–Kooij formula in five temperature intervals with a relative difference of <3%. The fit parameters will be added to the online database KIDA. For a temperature of 10–250 K, the rate constant is about 10−21 cm3 s−1, rising toward 10−16 cm3 s−1 for a temperature of 30 000 K.

  • 3634.
    Öztas, Ahmet M.
    et al.
    Hacettepe University, Ankara.
    Smith, Michael L.
    Anabolic Laboratories, Inc., Tempe, AZ.
    Paul, Jan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Spacetime curvature is important for cosmology constrained with supernova emissions2008In: International journal of theoretical physics, ISSN 0020-7748, E-ISSN 1572-9575, Vol. 47, no 9, p. 2464-2478Article in journal (Refereed)
    Abstract [en]

    We investigate universe expansion models as functions of emission frequency ratio decline rather than redshift z, using the latest on-line, self-consistent data from 192 supernovae. We present results for simpler and some current models of cosmology, including those with dark energy (standard model) and a recent model correcting for the effect of a small time-dependent, emission frequency increase with lookback. This new model, with a gentle lookback decline of the Planck constant, and the standard model fit the data with similar confidence according to Bayesian Information Criteria. The standard model tends towards solutions high in matter density while remaining flat, but models without dark energy tend towards dilute universes with significant spacetime and curvature and a smaller Hubble constant. We conclude the normalized spacetime parameter, Ω k , should not be ignored and it includes the combined contributions of huge spacetime magnitude and curvature.

  • 3635.
    Škultéty, Viktor
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Critical behaviour of directed percolation process in the presence of compressible velocity field2017Independent thesis Advanced level (degree of Master (Two Years)), 40 credits / 60 HE creditsStudent thesis
    Abstract [en]

    Renormalization group analysis is a useful tool for studying critical behaviour of stochastic systems. In this thesis, field-theoretic renormalization group will be applied to the scalar model representing directed percolation, known as Gribov model, in presence of the random velocity field. Turbulent mixing will be modelled by the compressible form of stochastic Navier-Stokes equation where the compressibility is described by an additional field related to the density. The task will be to find corresponding scaling properties.

70717273 3601 - 3635 of 3635
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