Now showing items 1-20 of 143

  • 3D PiC code investigations of Auroral Kilometric Radiation mechanisms 

    Gillespie, K. M.; McConville, S. L.; Speirs, D. C.; Ronald, K.; Phelps, A. D. R.; Bingham, R.; Cross, A. W.; Robertson, C. W.; Whyte, C. G.; He, W.; Vorgul, I.; Cairns, R. A.; Kellett, B. J. (IOP Publishing Ltd., 2014) - Conference item
    Efficient (similar to 1%) electron cyclotron radio emissions are known to originate in the X mode from regions of locally depleted plasma in the Earths polar magnetosphere. These emissions are commonly referred to as the ...
  • Algorithms for detecting dependencies and rigid subsystems for CAD 

    Farre, James; Kleinschmidt, Helena; Sidman, Jessica; John, Audrey St.; Stark, Stephanie; Theran, Louis; Yu, Xilin (2016-10-01) - Journal article
    Automated approaches for detecting dependencies in structures created with Computer Aided Design software are critical for developing robust solvers and providing informative user feedback. We model a set of geometric ...
  • The Assouad dimension of randomly generated fractals 

    Fraser, Jonathan MacDonald; Miao, Jun Jie; Troscheit, Sascha (2016-09-22) - Journal article
    We consider several dierent models for generating random fractals including random self-similar sets, random self-affine carpets, and Mandelbrot percolation. In each setting we compute either the almost sure or the Baire ...
  • The Assouad dimension of self-affine carpets with no grid structure 

    Fraser, Jonathan MacDonald; Jordan, Thomas (2016-12-21) - Journal article
    Previous study of the Assouad dimension of planar self-affine sets has relied heavily on the underlying IFS having a `grid structure', thus allowing for the use of approximate squares. We study the Assouad dimension of a ...
  • The Assouad dimensions of projections of planar sets 

    Fraser, Jonathan M.; Orponen, Tuomas (2017-02) - Journal article
    We consider the Assouad dimensions of orthogonal projections of planar sets onto lines. Our investigation covers both general and self-similar sets. For general sets, the main result is the following: if a set in the plane ...
  • Assouad type dimensions and homogeneity of fractals 

    Fraser, Jonathan M. (2014-12) - Journal article
    We investigate several aspects of the Assouad dimension and the lower dimension, which together form a natural 'dimension pair'. In particular, we compute these dimensions for certain classes of self-affine sets and ...
  • Attractors of directed graph IFSs that are not standard IFS attractors and their Hausdorff measure 

    Boore, Graeme; Falconer, Kenneth John (2013) - Journal article
    For directed graph iterated function systems (IFSs) defined on R, we prove that a class of 2-vertex directed graph IFSs have attractors that cannot be the attractors of standard (1-vertex directed graph) IFSs, with or ...
  • Automatic presentations and semigroup constructions 

    Cain, Alan J.; Oliver, Graham; Ruskuc, Nik; Thomas, Richard M. (2010-08) - Journal article
    An automatic presentation for a relational structure is, informally, an abstract representation of the elements of that structure by means of a regular language such that the relations can all be recognized by finite ...
  • Automatic presentations for semigroups 

    Cain, Alan James; Oliver, Graham; Ruskuc, Nik; Thomas, Richard M. (2009-11) - Journal article
    This paper applies the concept of FA-presentable structures to semigroups. We give a complete classification of the finitely generated FA-presentable cancellative semigroups: namely, a finitely generated cancellative ...
  • Automorphism groups of countable algebraically closed graphs and endomorphisms of the random graph 

    Dolinka, Igor; Gray, Robert Duncan; McPhee, Jillian Dawn; Mitchell, James David; Quick, Martyn (2016-05) - Journal article
    We establish links between countable algebraically closed graphs and the endomorphisms of the countable universal graph R. As a consequence we show that, for any countable graph Γ, there are uncountably many maximal subgroups ...
  • Average distances on self-similar sets and higher order average distances of self-similar measures 

    Allen, D.; Edwards, H.; Harper, S.; Olsen, Lars Ole Ronnow (2016-12-29) - Journal article
    The purpose of this paper is twofold: (1) We study different notions of the average distance between two points of a self-similar subset of ℝ, and (2) we investigate the asymptotic behaviour of higher order average moments ...
  • Backward wave cyclotron-maser emission in the auroral magnetosphere 

    Speirs, D. C.; Bingham, R.; Cairns, R. A.; Vorgul, I.; Kellett, B. J.; Phelps, A. D. R.; Ronald, K. (2014-10-07) - Journal article
    In this Letter, we present theory and particle-in-cell simulations describing cyclotron radio emission from Earth's auroral region and similar phenomena in other astrophysical environments. In particular, we find that the ...
  • The Bergman property for semigroups 

    Maltcev, V.; Mitchell, J. D.; Ruskuc, N. (2009-08) - Journal article
    In this article, we study the Bergman property for semigroups and the associated notions of cofinality and strong cofinality. A large part of the paper is devoted to determining when the Bergman property, and the values ...
  • Bernoulli convolutions and 1D dynamics 

    Kempton, Thomas Michael William; Persson, Tomas (2015-10-08) - Journal article
    We describe a family φλ of dynamical systems on the unit interval which preserve Bernoulli convolutions. We show that if there are parameter ranges for which these systems are piecewise convex, then the corresponding ...
  • Between primitive and 2-transitive : synchronization and its friends 

    Araújo, João; Cameron, Peter Jephson; Steinberg, Benjamin (2017-06-15) - Journal article
    An automaton (consisting of a finite set of states with given transitions) is said to be synchronizing if there is a word in the transitions which sends all states of the automaton to a single state. Research on this topic ...
  • Beyond sum-free sets in the natural numbers 

    Huczynska, Sophie (2014-02-07) - Journal article
    For an interval [1,N]⊆N, sets S⊆[1,N] with the property that |{(x,y)∈S2:x+y∈S}|=0, known as sum-free sets, have attracted considerable attention. In this paper, we generalize this notion by considering r(S)=|{(x,y)∈S2:x+y∈S}|, ...
  • Cancellative and Malcev presentations for finite Rees index subsemigroups and extensions 

    Cain, Alan James; Robertson, Edmund Frederick; Ruskuc, Nik (2008-02) - Journal article
    It is known that, for semigroups, the property of admitting a finite presentation is preserved on passing to subsemigroups and extensions of finite Rees index. The present paper shows that the same holds true for Malcev, ...
  • Catastrophe versus instability for the eruption of a toroidal solar magnetic flux rope 

    Kliem, B.; Lin, J.; Forbes, T. G.; Priest, E. R.; Toeroek, T. (2014-07-01) - Journal article
    The onset of a solar eruption is formulated here as either a magnetic catastrophe or as an instability. Both start with the same equation of force balance governing the underlying equilibria. Using a toroidal flux rope in ...
  • The classification of partition homogeneous groups with applications to semigroup theory 

    André, Jorge; Araúo, Joāo; Cameron, Peter Jephson (2016-04-15) - Journal article
    Let λ=(λ1,λ2,...) be a partition of n, a sequence of positive integers in non-increasing order with sum n. Let Ω:={1,...,n}. An ordered partition P=(A1,A2,...) of Ω has type λ if |Ai|=λi.Following Martin and Sagan, we say ...
  • Codimension formulae for the intersection of fractal subsets of Cantor spaces 

    Donoven, Casey; Falconer, Kenneth John (2016-02) - Journal article
    We examine the dimensions of the intersection of a subset E of an m-ary Cantor space Cm with the image of a subset F under a random isometry with respect to a natural metric. We obtain almost sure upper bounds for the ...