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Fluid Dynamics of Parallel Plates Viscometer: a Case Study of Methods Of Series Summation
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: O.D. MakindeThe fluid dynamics of parallel plates viscometer is investigated mathematically using both the Navier-Stokes and continuity equations for an incompressible viscous fluid. The problem admits similarity solutions, thereby reducing the unsteady Navier-Stokes equations to a parameter dependent fourth order nonlinear... -
Stability of asymptotic properties of Hille-yosida operators under perturbations and retarded differential equations
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Lahcen ManiarWe give conditions on the strongly continuous semigroup (T 0(t)) t≥0, generated by the part of a Hille-Yosida operator A on X 0 := D(A), and a non-autonomous family of operators (B(t)) t≥0 such that the evolution family (U(t,s)) t≥s≥0,... -
Compact perturbations and norm attaining operators
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Janice KoverIn 1963, Lindenstrauss showed that for a reflexive space, X, and any Banach space,Y, that the norm attaining operators in L(X, Y) are dense. Recall that a linear operator A is norm attaining if there exists a unit vector x... -
Perturbations by norm attaining operators
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Janice KoverIn this note, we develop a connection between Fredholm operators and norm attaining operators in the set L(H) of bounded linear operators on a Hilbert space. We use this connection to extend an earlier result about the stability of norm... -
Comparison of assemblages and some life-history traits of seabirds in the Humboldt and Benguela systems
Item type: Journal Article • Journal: African Journal of Marine Science • Authors: RJM Crawford E Goya J-P Roux CB ZavalagaThere are 21 and 15 species of seabirds that breed in the Humboldt and Benguela upwelling systems respectively. Only two species of gull are common to both systems, one as an endemic subspecies to the Benguela system. Eleven species and... -
Reliable finite element methods for self-adjoint singular perturbation problems
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: JeanM.-S. Lubuma --- Department of Mathematics and Applied Mathematics, South Africa KailashC. Patidar --- Department of Mathematics and Applied Mathematics, South AfricaIt is well known that the standard finite element method based on the space Vh of continuous piecewise linear functions is not reliable in solving singular perturbation problems. It is also known that the solution of a two-point boundary-value singular... -
Macroinvertebrate distributions in relation to human and animal-induced physical disturbance of the sediment surface in two Kenyan tropical Rift Valley streams
Item type: Journal Article • Journal: African Journal of Aquatic Science • Authors: CM M'Erimba --- Department of Biological Sciences, Kenya JM Mathooko --- Global Research Akademik and Mentoring Services, Kenya KO Ouma --- Department of Biological Sciences, KenyaA study of macroinvertebrate distribution in relation to different levels of human and animal physical disturbance of the sediments of the Njoro (highly disturbed) and Ellegirini (less disturbed) rivers was conducted from October 2001 to June 2002, and again in... -
A note on a conjecture concerning rank one perturbations of singular M-matrices
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: B. Anehila --- ROC Mondriaan, The Netherlands A.C.M. Ran --- VU Amsterdam, The NetherlandsA conjecture from [3] concerning the location of eigenvalues of rank one perturbations of singular M-matrices is shown to be false in dimension four and higher, but true for dimension two, as well as for dimension three with an additional... -
Comultiplication structures on the wedge product of spheres
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Dae-Woong Lee --- Jeonbuk National University, Republic of Korea Sunyoung Lee --- Jeonbuk National University, Republic of KoreaHomotopy multiplications on H-spaces and homotopy comultiplications on co-H-spaces play an important role in topology for many reasons. They are the duals with each other in the sense of Eckmann and Hilton, and have many kinds of examples to construct... -
Perturbations with nonpositive Lyapunov exponents
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Luis Barreira --- Instituto Superior Técnico, Universidade de Lisboa, Portugal Claudia Valls --- Instituto Superior Técnico, Universidade de Lisboa, PortugalThe notion of uniform hyperbolicity is equivalent to various admissibility properties. For example, one such property is expressed in terms of the existence of bounded solutions for any bounded perturbation of the dynamics. Our main objective is to describe a... -
Periodic solution for perturbed Hamiltonian systems
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Khaled Khachnaoui --- University of Kairouan, TunisiaIn this paper, we study the existence of infinitely many periodic solutions for second-order perturbed Hamiltonian systems. By using variational methods, we obtain new criteria to guarantee the existence of infinitely many periodic solutions using Bolle’s perturbation method. Our results... -
A fully discrete scheme on piecewise-equidistant mesh for singularly perturbed delay integro-differential equations
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Musa Cakir --- Van Yuzuncu Yil University, Turkey Baransel Gunes --- Van Yuzuncu Yil University, TurkeyThis paper chiefly takes into account the singularly perturbed delay Volterra-Fredholm integro-differential equations by numerically. In this context, firstly, priori estimates are given and a new discretization is constructed on piecewise-equidistant mesh by using interpolating quadrature rules [2] and composite... -
Asymptotical convergence of solutions of boundary value problems for singularly perturbed higher-order integro-differential equations
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: M.K. Dauylbayev --- Al-Farabi Kazakh National University, Kazakhstan K.T. Konisbayeva --- Al-Farabi Kazakh National University, KazakhstanThe article considers a two-point boundary value problem for a linear integro-differential equation of the n + m order with small parameters for m higher derivatives, provided that the roots of the additional characteristic equation are negative. The aim of... -
Adaptive grid based moving mesh algorithms for singularly perturbed second-order Volterra integro differential equations
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Sushree Priyadarshana --- Centre for Data Science, Institute of Technical Education and Research, SOA Deemed to be University, India Ajaya Padhan --- National Institute of Technology Rourkela, India Jugal Mohapatra --- National Institute of Technology Rourkela, IndiaRobust adaptive grid-based moving mesh algorithms are discussed for singularly perturbed second-order convection-diffusion type Volterra integro differential equations. Two different kinds of monitor functions are used to establish the numerical schemes. A well-studied first-order monitor function is used to construct... -
One-sided Drazin invertibility in Banach algebras and perturbations of B-Fredholm spectra
Item type: Journal Article • Journal: Quaestiones Mathematicae • Authors: Kai Yan --- Fuzhou University, P.R. ChinaThe famous Drazin inverse and generalized Drazin inverse were originally introduced by Drazin in 1958 and Koliha in 1996, respectively. In this paper, the author presents simplified notions of left and right (generalized) Drazin inverses, which are the one-sided versions...