Browsing Research Articles (Mathematical Sciences) by Title

Now showing items 2-21 of 22

    • Calculating the output distribution of stack filters that are erosion-dilation cascades, in particular LULU-filters 

      Anguelov, R.; Butler, P. W.; Rohwer, C. H.; Wild, Marcel (Cornell University Library, 2011)
      ENGLISH ABSTRACT: Two procedures to compute the output distribution 0S of certain stack filters S (so called erosion-dilation cascades) are given. One rests on the disjunctive normal form of S and also yields the rank ...

    • Codon test : modeling amino acid substitution preferences in coding sequences 

      Delport, Wayne; Scheffler, Konrad; Botha, Gordon; Gravenor, Mike B.; Muse, Spencer V.; Pond, Sergei L. Kosakovsky (PLOS Computational Biology, 2010-08)
      Codon models of evolution have facilitated the interpretation of selective forces operating on genomes. These models, however, assume a single rate of non-synonymous substitution irrespective of the nature of amino acids ...

    • Compactly generating all satisfying truth assignments of a horn formula 

      Wild, Marcel (Delft University in cooperation with IOS Press, 2012-01)
      ENGLISH ABSTRACT: While it was known that all models of a Horn formula can be generated in outputpolynomial time, here we present an explicit algorithm as opposed to the rather vague oracle-scheme suggested in the proof ...

    • Computing the output distribution of a stack filter from the DNF of its positive Boolean function 

      Wild, Marcel (Cornell University Library, 2010)
      ENGLISH ABSTRACT: The majority of nonlinear filters used in practise are stack filters. An algorithm is presented which calculates the output distribution of an arbitrary stack filter S from the disjunctive normal form ...

    • Computing various types of lattices freely generated by posets 

      Wild, Marcel (Edizioni CERFIM Centro di Ricerche in Fisica e MatematicaResearch Center for Mathematics and Physics - Locarno - Switzerland, 2000)
      see item for abstract

    • Correcting the bias of empirical frequency parameter estimators in codon models 

      Kosakovsky Pond, Sergei; Delport, Wayne; Muse, Spencer V.; Scheffler, Konrad (Public Library of Science -- PLOS, 2010-07)
      Markov models of codon substitution are powerful inferential tools for studying biological processes such as natural selection and preferences in amino acid substitution. The equilibrium character distributions of these ...

    • Decomposing the hypercube Qn into n isomorphic edge-disjoint trees 

      Wagner, Stephan; Wild, Marcel (Elsevier, 2012-02)
      The problem of finding edge-disjoint trees in a hypercube arises for example in the context of parallel computing [3]. Independently of applications it is of high aesthetic appeal. The hypercube of dimension n, denoted ...

    • Francis Guthrie : a colourful life 

      Maritz, Pieter; Mouton, Sonja (Springer, 2012-09)
      In 1852, in London, Francis Guthrie posed the question of colouring a map with four colours only, the question that eventually became known as the Four Colour Problem. The problem is famous, but what else do we know of ...

    • The geometry of unitary 2-representations of finite groups and their 2-characters 

      Bartlett, Bruce (Springer Link, 2011-02)
      Motivated by topological quantum field theory, we investigate the geometric aspects of unitary 2-representations of finite groups on 2-Hilbert spaces, and their 2-characters. We show how the basic ideas of geometric ...

    • Left ventricular segmentation from MRI datasets with edge modelling conditional random fields 

      Dreijer, Janto F.; Herbst, Ben M.; Du Preez, Johan A. (BioMed Central, 2013-07)
      Background: This paper considers automatic segmentation of the left cardiac ventricle in short axis magnetic resonance images. Various aspects, such as the presence of papillary muscles near the endocardium border, makes ...

    • Model checking rational agents 

      Bordini, Rafael H.; Fisher, Michael; Wooldridge, Michael; Visser, Willem (IEEE - -Institute of Electrical and Electronics Engineers, 2004-10)
      Agent-oriented programming techniques seem appropriate for developing systems that operate in complex, dynamic, and unpredictable environments. We aim to address this requirement by developing model-checking techniques for ...

    • Modeling HIV-1 drug resistance as episodic directional selection 

      Murrell, Ben; De Oliveira, Tulio; Seebregts, Chris; Pond, Sergei L. Kosakovsky; Scheffler, Konrad (PLOS Computational Biology, 2011-05)
      The evolution of substitutions conferring drug resistance to HIV-1 is both episodic, occurring when patients are on antiretroviral therapy, and strongly directional, with site-specific resistant residues increasing in ...

    • Non-Negative Matrix Factorization for Learning Alignment-Specific Models of Protein Evolution 

      Murrell, Ben; Weighill, Thomas; Buys, Jan; Ketteringham, Robert; Moola, Sasha; Benade, Gerdus; du Buisson, Lise; Kaliski, Daniel; Hands, Tristan; Scheffler, Konrad (PLOS, 2011-12-22)
      Models of protein evolution currently come in two flavors: generalist and specialist. Generalist models (e.g. PAM, JTT, WAG) adopt a one-size-fits-all approach, where a single model is estimated from a number of different ...

    • On the validity of evolutionary models with site-specific parameters 

      Scheffler, Konrad; Murrell, Ben; Pond, Sergei L. Kosakovsky (PLoS, 2014-04-10)
      Evolutionary models that make use of site-specific parameters have recently been criticized on the grounds that parameter estimates obtained under such models can be unreliable and lack theoretical guarantees of convergence. ...

    • Partitioning the hypercube Qn into n isomorphic edge-disjoint trees 

      Wagner, Stephan; Wild, Marcel (TU Graz University of Technology, 2011)
      ENGLISH ABSTRACT: The problem of finding edge-disjoint trees in a hypercube e.g. arises in the context of parallel computing. Independent of applications it is of high aesthetic appeal.

    • Property-based slicing for agent verification 

      Bordini, Rafael H.; Fisher, Michael; Wooldridge, Michael; Visser, Willem (Oxford University Press (OUP), 2009-12)
      Programming languages designed specifically for multi-agent systems represent a new programming paradigm that has gained popularity over recent years, with some multi-agent programming languages being used in increasingly ...

    • Realization of abstract convex geometries by point configurations 

      Adaricheva, Kira; Wild, Marcel (Elsevier, 2010-01)
      The Edelman-Jamison problem is to characterize those abstract convex geometries that are representable by a set of points in the plane. We show that some natural modification of the Edelman-Jamison problem is equivalent ...

    • Spatial assortment of mixed propagules explains the acceleration of range expansion 

      Ramanantoanina, Andriamihaja; Ouhinou, Aziz; Hui, Cang (Public Library of Science, 2014-08)
      Abstract Range expansion of spreading organisms has been found to follow three types: (i) linear expansion with a constant rate of spread; (ii) bi-phase expansion with a faster linear expansion following a slower linear ...

    • Special subvarieties of Drinfeld modular varieties 

      Breuer, Florian (Walter de Gruyter, 2010-11)
      We explore an analogue of the Andr´e-Oort conjecture for subvarieties of Drinfeld modular varieties. The conjecture states that a subvariety X of a Drinfeld modular variety contains a Zariski-dense set of complex ...

    • Die Suid-Afrikaanse uitgebreide maritieme gebied : ’n alternatiewe metode vir die bepaling van die voet van die kontinentale helling 

      Pantland, N. A.; Van Vuuren, J. H. (AOSIS OpenJournal, 2006)
      Kuslande het ’n eenmalige geleentheid om by die Verenigde Nasies (VN) aansoek te doen om ’n uitgebreide maritieme gebied, indien hul wetenskaplik kan toon dat die voet van die kontinentale helling (VKH) buite hul soewereine ...