Now showing items 65-84 of 345

  • Control of scroll-wave turbulence using resonant perturbations 

    Morgan, S. W.; Biktasheva, I. V.; Biktashev, V. N. (American Physical Society, 2008)
    Turbulence of scroll waves is a sort of spatiotemporal chaos that exists in three-dimensional excitable media. Cardiac tissue and the Belousov-Zhabotinsky reaction are examples of such media. In cardiac tissue, chaotic ...
  • Control-based continuation of unstable periodic orbits 

    Sieber, J.; Krauskopf, Bernd; Wagg, David; Neild, Simon; Gonzalez-Buelga, A. (American Society of Mechanical Engineers (ASME), 2011)
    We present an experimental procedure to track periodic orbits through a fold (saddle-node) bifurcation and demonstrate it with a parametrically excited pendulum experiment where the tracking parameter is the amplitude of ...
  • Controlling unstable chaos: stabilizing chimera states by feedback 

    Sieber, J.; Omel'chenko, Oleh E.; Wolfrum, Matthias (American Physical Society, 2014)
    We present a control scheme that is able to find and stabilize an unstable chaotic regime in a system with a large number of interacting particles. This allows us to track a high dimensional chaotic attractor through a ...
  • Convergence to local random attractors 

    Ashwin, Peter; Ochs, Gunter (Taylor & Francis, 2003)
    Random attractors allow one to classify qualitative and quantitative aspects of the long-time behaviour of stochastically forced systems viewed as random dynamical systems (RDS) in an analogous way to attractors for ...
  • Coronal Alfvén speed determination : consistency between seismology using AIA/SDO transverse loop oscillations and magnetic extrapolation 

    Verwichte, E.; Van Doorsselaere, T.; Foullon, Claire; White, R.S. (American Astronomical Society / IOP Publishing, 2013)
    Two transversely oscillating coronal loops are investigated in detail during a flare on the 2011 September 6 using data from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory. We compare two ...
  • A counterexample to "positive realness preserving model reduction with ℋ∞ norm error bounds" 

    Guiver, Chris; Opmeer, Mark R. (Institute of Electrical and Electronics Engineers (IEEE), 2011)
    We provide a counterexample to the H∞ error bound for the difference of a positive real transfer function and its positive real balanced truncation stated in “Positive realness preserving model reduction with H∞ norm error ...
  • Countertraveling waves in rotating Rayleigh-Bénard convection. 

    Li, Ligang; Liao, X.; Zhang, Keke (American Physical Society, 2008)
    Linear and nonlinear counter-traveling waves in a fluid-filled annular cylinder with realistic no-slip boundary conditions uniformly heated from below and rotating about a vertical axis are investigated. When the gap of ...
  • Criteria for robustness of heteroclinic cycles in neural microcircuits. 

    Ashwin, Peter; Karabacak, Ozkan; Nowotny, Thomas (BioMed Central / SpringerOpen, 2011)
    We introduce a test for robustness of heteroclinic cycles that appear in neural microcircuits modeled as coupled dynamical cells. Robust heteroclinic cycles (RHCs) can appear as robust attractors in Lotka-Volterra-type ...
  • Critical fronts in initiation of excitation waves 

    Idris, I.; Biktashev, V. N. (American Physical Society, 2007)
    We consider the problem of initiation of propagating waves in a one-dimensional excitable fiber. In the FitzHugh-Nagumo theory, the key role is played by "critical nucleus" and "critical pulse" solutions whose (center-) ...
  • Cycling chaos: its creation, persistence and loss of stability in a model of nonlinear magnetoconvection 

    Ashwin, Peter; Rucklidge, Alastair M. (Elsevier, 1998)
    We examine a model system where attractors may consist of a heteroclinic cycle between chaotic sets; this `cycling chaos' manifests itself as trajectories that spend increasingly long periods lingering near chaotic invariant ...
  • Cycling chaotic attractors in two models for dynamics with invariant subspaces 

    Ashwin, Peter; Rucklidge, Alastair M.; Sturman, Rob (American Institute of Physics, 2004)
    Nonergodic attractors can robustly appear in symmetric systems as structurally stable cycles between saddle-type invariant sets. These saddles may be chaotic giving rise to "cycling chaos." The robustness of such attractors ...
  • Damped large amplitude transverse oscillations in an EUV solar prominence, triggered by large-scale transient coronal waves 

    Hershaw, J.; Foullon, Claire; Nakariakov, V.M.; Verwichte, E. (EDP Sciences, 2011)
    Aims. We investigate two successive trains of large amplitude transverse oscillations in an arched EUV prominence, observed with SoHO/EIT on the north-east solar limb on 30 July 2005. The oscillatory trains are triggered ...
  • Decelerating defects and non-ergodic critical behaviour in a unidirectionally coupled map lattice 

    Ashwin, Peter; Sturman, Rob (Elsevier, 2003)
    We examine a coupled map lattice (CML) consisting of an infinite chain of logistic maps coupled in one direction by inhibitory coupling. We find that for sufficiently strong coupling strength there are dynamical states ...
  • Declining summer snowfall in the Arctic: Causes, impacts and feedbacks 

    Screen, James A.; Simmonds, Ian (Springer Verlag, 2012)
    Recent changes in the Arctic hydrological cycle are explored using in situ observations and an improved atmospheric reanalysis data set, ERA-Interim. We document a pronounced decline in summer snowfall over the Arctic Ocean ...
  • Dengue epidemic early warning system for Brazil 

    Lowe, Rachel; Rodo, X.; Barcellos, Christovam; Carvalho; Coelho, Caio A.S.; Bailey, Trevor C.; Jupp, Tim E.; Stephenson, David B.; Coelho, G.E.; Graham, Richard J.; Ramalho, W.M. (UNISDR Scientific and Technical Advisory Group, 2015)
    The problem Brazil has reported more cases of dengue fever than anywhere else in the world this century1. Many cities have tropical and sub-tropical climate conditions that allow the dengue mosquito to thrive during warmer, ...
  • Dependency of global mean precipitation on surface temperature 

    Lambert, F. Hugo; Webb, Mark J. (American Geophysical Union (AGU), 2008)
    We investigate the causes of temperature dependent changes in global precipitation in contemporary General Circulation Models (GCMs) subjected to a doubling of atmospheric CO2 concentration. By analyzing the energy budget ...
  • Designing the dynamics of globally coupled oscillators 

    Orosz, Gábor; Moehlis, Jeff; Ashwin, Peter (Oxford University Press, 2009)
    A method for designing cluster states with prescribed stability is presented for coupled phase oscillator systems with all-to-all coupling. We determine criteria for the coupling function that ensure the existence and ...
  • Detection of ultra-long-period oscillations in an EUV filament 

    Foullon, Claire; Verwichte, E.; Nakariakov, V.M. (EDP Sciences, 2004)
    We report the first detection of long-period (8-27 h) oscillatory intensity variations in a coronal filament. The filament is observed continuously as it crosses the solar disk in a 12-min-cadence SoHO/EIT 195 Å uninterrupted ...
  • The development of an early warning system for climate-sensitive disease risk with a focus on dengue epidemics in Southeast Brazil 

    Lowe, Rachel; Bailey, Trevor C.; Stephenson, David B.; Jupp, Tim E.; Graham, Richard J.; Barcellos, Christovam; Carvalho, Marilia Sa (2013)
    Previous studies demonstrate statistically significant associations between disease and climate variations, highlighting the potential for developing climate-based epidemic early warning systems. However, limitations include ...
  • Diffusion and the formation of vorticity staircases in randomly strained two-dimensional vortices 

    Turner, M.R.; Bassom, Andrew P.; Gilbert, Andrew D. (Cambridge University Press, 2009)
    The spreading and diffusion of two-dimensional vortices subject to weak external random strain fields is examined. The response to such a field of given angular frequency depends on the profile of the vortex and can be ...