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Natural Alternatives For One Dimensional Median Filtering
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: C.H. Rohwer M. WildFor practical purposes median smoothers have often been considered the basic components for the construction of simple non-linear smoothers for removing impulsive noise before any subsequent linear signal extraction from a sequence. Alternatives exist that are computationally convenient, conceptually simpler... -
Variation Reduction and Lu Lu-smoothing
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: C.H. RohwerIn the space of absolutely summable sequences the total variation of a sequence becomes a natural norm, and is a measure of smoothness. This norm is preserved by the so-called LU LU-smoothers, in that the variation of the image plus... -
The
Lu Lu -semigroup for Envelopes Of Functions Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: E. Malkowsky C.H. RohwerIn the theory of non-linear smoothers a semigroup of operators has been established, that structures the rank based selectors in a lattice for the purpose of comparison and analysis. The well known upper and lower envelopes of functions can be... -
Fully Trend Preserving Operators
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: C.H. RohwerThe concept of fully trend preserving (ftp) operators on sequences was introduced to prove variation preservation on the outputs of LULU-separators. It turns out that this property is central in further analysis of compositions of LULU-smoothers, and other smoothers. Several... -
On the way to Frölicher Lie groups
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: P.P. Ntumba T.A. BatubengeIn this paper, we start by showing that one can obtain by way of diffeomorphisms some classical smooth curves and surfaces. The notion of bundles is also introduced in the category of Frölicher spaces, and one may carry on investigating... -
Boman's theorem: Strengthened and applied
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: H. L. Bentley Paul CherenackA 1-variable calculus type argument is used to show that, for a function f : R 2 → R, if for all (a, b) ∈ R 2 we have that f o c is smooth for every smooth curve c... -
Quasi-inverses and approximation with min-max operators in the ℓ1-norm
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: C.H. RohwerThe semi-group of min-max operators, as used for nonlinear smoothing or multiresolution analysis, has no nontrivial inverses. Having chosen a smoother for a specific purpose, the secondary approximation problem of minimising damage was considered by showing that quasi-inverses exist. This... -
Rotundity in transitive and separable Banach spaces
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: A. Aizpuru F.J. García-PachecoIn every separable Banach space the set of smooth points of the unit ball is a Gδ dense subset of the unit sphere. In this paper, we find some conditions in order to obtain a similar result for rotund points... -
Interpreting behavioural data from Radio-Acoustic Positioning Telemetry (RAPT) systems
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: PR Rigby Y Andrade RK O'DorTo detect behavioural patterns of individually tagged squid Loligo vulgaris reynaudii in a Radio-Acoustic Positioning Telemetry (RAPT) buoy array, trajectories reflecting the four dimensions of latitude, longitude, depth and time were plotted from data collected during field experiments in South... -
LULU operators for functions of continuous argument
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Roumen Anguelov Carl RohwerThe LULU operators, well known in the nonlinear multiresolution analysis of sequences, are extended to functions defined on a continuous domain, namely, a real interval. We show that the extended operators replicate the essential properties of their discrete counterparts. More... -
Extraordinary items: Accounting and market risk
Item type: Journal Article • Journal: South African Journal of Accounting Research • Authors: J A Miller --- Emeritus Professor in Accounting and Finance,The market reaction to the recurrent reporting of extraordinary items was tested by calculating and comparing the betas for a portfolio of shares that reported extraordinary items in each of the five years 1990 through 1994 and a control portfolio... -
Profit smoothing in industrial companies listed on the Johannesburg Stock Exchange
Item type: Journal Article • Journal: De Ratione • Authors: K E Prinsloo --- Department of Accounting, S D Ramsay-Slogrove --- Department of Accounting, J E Rowlands --- Department of Accounting,This study evaluated the extent to which profit smoothing is practised in the industrial sector of the Johannesburg Stock Exchange (JSE), identified the smoothing dimensions most likely to be used and evaluated the impact of ex ante profit patterns on... -
Human immunodeficiency virus-related Epstein-Barr virus-associated smooth muscle tumours: South African experience from Chris Hani Baragwanath Academic Hospital
Item type: Journal Article • Journal: Southern African Journal of Infectious Diseases • Authors: Sugeshnee Pather --- Division of Anatomical Pathology, National Health Laboratory Service, South Africa Rosalind D. Wainwright --- Haematology and Oncology Unit, Department of Paediatrics, South Africa Faieza Sahid --- Division of Infectious Diseases, Department of Internal Medicine, South Africa Thembi Mashele --- Division of Anatomical Pathology, National Health Laboratory Service, South Africa Eunice J. van den Berg --- Division of Anatomical Pathology, National Health Laboratory Service, South Africa Reena D. Mohanlal --- Division of Anatomical Pathology, National Health Laboratory Service, South AfricaBackground: Despite the rampant human immunodeficiency (HIV) epidemic in Africa, there is a paucity of published data of HIV-related Epstein-Barr virus-associated smooth muscle tumours (EBV-SMT) from Africa. -
Predicting soil carbon in granitic soils using Fourier-transform mid-infrared (FT-MIR) spectroscopy: the value of database disaggregation
Item type: Journal Article • Journal: South African Journal of Plant and Soil • Authors: Kelebohile Rose Seboko --- University of the Free State, South Africa Johan van Tol --- University of the Free State, South Africa Elmarie Kotze --- University of the Free State, South AfricaSoil carbon (C) is an important component in quality assessments and efficient models are required to estimate C rapidly. Accurate C assessments are valuable in monitoring land-use changes. Fourier-transform mid-infrared (FT-MIR) spectroscopy has proved to be a powerful tool for... -
Differential geometry of Hom-Lie algebras and Hom-Lie algebroids
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Bayram Şahin --- Ege University, Turkey Fulya Şahin --- Ege University, TurkeyIn this paper, the geometry of Hom-Lie algebras and Hom-Lie algebroids are studied. In this direction, the effects of connections on Hom-Lie algebras and Hom-Lie algebroids are first investigated. By finding the relations among hom-curvature operator, torsion and connection on... -
Flows with constant slope on the Klein bottle
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Luís Barreira --- Universidade de Lisboa, Portugal Jaume Llibre --- Universitat Autònoma de Barcelona, Spain Claudia Valls --- Instituto Superior Técnico, Universidade de Lisboa, PortugalWe consider smooth flows with constant slope on the 2-dimensional (flat) torus and on the (flat) Klein bottle. It is well known that for a flow with constant slope on the torus either all orbits are periodic or all orbits... -
On asymptotically almost periodic mild solutions of chemotaxis-fluid systems on bounded domains
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Dam Thi Ngoc Van --- Division of Mathematics, Banking Academy of Vietnam, Vietnam Tran Minh Nguyet --- Department of Mathematics, Thang Long University, Vietnam Pham Truong Xuan --- Thang Long University, VietnamWe study the well-posedness and exponential stability of almost periodic (AP-) and asymptotically almost periodic (AAP-) mild solutions for the chemotaxis-Navier-Stokes systems on a bounded domain Ω ⊂ ℝd (d ⩾ 2) with the smooth boundary. Our strategy is: we...