4,429 research outputs found
Discrete-Time System of an Intracellular Delayed HIV Model with CTL Immune Response
In [Math. Comput. Sci. 12 (2018), no. 2, 111--127], a delayed model
describing the dynamics of the Human Immunodeficiency Virus (HIV) with
Cytotoxic T Lymphocytes (CTL) immune response is investigated by Allali,
Harroudi and Torres. Here, we propose a discrete-time version of that model,
which includes four nonlinear difference equations describing the evolution of
uninfected, infected, free HIV viruses, and CTL immune response cells and
includes intracellular delay. Using suitable Lyapunov functions, we prove the
global stability of the disease free equilibrium point and of the two endemic
equilibrium points. We finalize by making some simulations and showing,
numerically, the consistence of the obtained theoretical results.info:eu-repo/semantics/publishedVersio
THERMAL POST-BUCKLING OF SLENDER ELASTIC RODS WITH DIFFERENT BOUNDARY CONDITIONS
This paper presents mathematical formulation, critical buckling temperature and analytical and numerical solutions for the thermal post-buckling behavior of slender rods subjected to uniform thermal load. The material is assumed to be linear elastic, homogeneous and isotropic. Furthermore, large displacements are considered hence the formulation is geometrically non-linear. Three different boundary conditions are assumed: (i) double-hinged non-movable, (ii) hinged non-movable at one end, whereas at the other end longitudinal displacement is constrained by a linear spring, and (iii) double-fixed non-movable. The governing equations are derived from geometrical compatibility, equilibrium of forces and moments, constitutive equations and strain-displacement relation, yielding a set of six first-order non-linear ordinary differential equations with boundary conditions specified at both ends, which constitutes a complex boundary value problem. The buckling and post-buckling solutions are respectively accomplished assuming infinitesimal and finite rotations. The results are presented in non-dimensional graphs for a range of temperature gradients and different values of slenderness ratios, and it is shown that this parameter governs the rod post-buckling response. The influence of the boundary conditions is evaluated through graphic results for deformed configuration, maximum deflection, maximum inclination angle and maximum curvature in the rod
A discrete-time compartmental epidemiological model for COVID-19 with a case study for Portugal
Recently, a continuous-time compartmental mathematical model for the spread of the
Coronavirus disease 2019 (COVID-19) was presented with Portugal as case study, from 2 March to
4 May 2020, and the local stability of the Disease Free Equilibrium (DFE) was analysed. Here, we
propose an analogous discrete-time model and, using a suitable Lyapunov function, we prove the
global stability of the DFE point. Using COVID-19 real data, we show, through numerical simulations,
the consistence of the obtained theoretical results.publishe
Discrete-Time System of an Intracellular Delayed HIV Model with CTL Immune Response
In [Math. Comput. Sci. 12 (2018), no. 2, 111--127], a delayed model
describing the dynamics of the Human Immunodeficiency Virus (HIV) with
Cytotoxic T Lymphocytes (CTL) immune response is investigated by Allali,
Harroudi and Torres. Here, we propose a discrete-time version of that model,
which includes four nonlinear difference equations describing the evolution of
uninfected, infected, free HIV viruses, and CTL immune response cells and
includes intracellular delay. Using suitable Lyapunov functions, we prove the
global stability of the disease free equilibrium point and of the two endemic
equilibrium points. We finalize by making some simulations and showing,
numerically, the consistence of the obtained theoretical results.Comment: This is a preprint whose final form is published by Springer Nature
Switzerland AG in the book 'Dynamic Control and Optimization
Determinação eletroanalítica do pesticida paration metílico em eletrodo de carbono vítreo.
bitstream/CNPDIA-2009-09/11854/1/DOC26_2006.pd
Screening in two-dimensional foams
Using the Surface Evolver software, we perform numerical simulations of
point-like deformations in a two-dimensional foam. We study perturbations which
are infinitesimal or finite, isotropic or anisotropic, and we either conserve
or do not conserve the number of bubbles. We measure the displacement fields
around the perturbation. Changes in pressure decrease exponentially with the
distance to perturbation, indicating a screening over a few bubble diameters
General spherically symmetric elastic stars in Relativity
The relativistic theory of elasticity is reviewed within the spherically
symmetric context with a view towards the modeling of star interiors possessing
elastic properties such as theones expected in neutron stars. Emphasis is
placed on generality in the main sections of the paper, and the results are
then applied to specific examples. Along the way, a few general results for
spacetimes admitting isometries are deduced, and their consequences are fully
exploited in the case of spherical symmetry relating them next to the the case
in which the material content of the spacetime is some elastic material. This
paper extends and generalizes the pioneering work by Magli and Kijowski [1],
Magli [2] and [3], and complements, in a sense, that by Karlovini and
Samuelsson in their interesting series of papers [4], [5] and [6].Comment: 23 page
Desenvolvimento de metodologias eletroanalíticas para a determinação de pesticidas em óleo essencial de laranja.
Switching of +/-360deg domain wall states in a nanoring by an azimuthal Oersted field
We demonstrate magnetic switching between two domain wall vortex
states in cobalt nanorings, which are candidate magnetic states for robust and
low power MRAM devices. These domain wall (DW) or "twisted onion"
states can have clockwise or counterclockwise circulation, the two states for
data storage. Reliable switching between the states is necessary for any
realistic device. We accomplish this switching by applying a circular Oersted
field created by passing current through a metal atomic force microscope tip
placed at the center of the ring. After initializing in an onion state, we
rotate the DWs to one side of the ring by passing a current through the center,
and can switch between the two twisted states by reversing the current, causing
the DWs to split and meet again on the opposite side of the ring. A larger
current will annihilate the DWs and create a perfect vortex state in the rings.Comment: 5 pages, 5 figure
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