| 1. |
- Andersson, Jonathan, et al.
(författare)
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Density-Dependent Feedback in Age-Structured Populations
- 2019
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Ingår i: Journal of Mathematical Sciences. - : Springer Berlin/Heidelberg. - 1072-3374 .- 1573-8795. ; 242:1, s. 2-24
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Tidskriftsartikel (refereegranskat)abstract
- The population size has far-reaching effects on the fitness of the population, that, in its turn influences the population extinction or persistence. Understanding the density- and age-dependent factors will facilitate more accurate predictions about the population dynamics and its asymptotic behaviour. In this paper, we develop a rigourous mathematical analysis to study positive and negative effects of increased population density in the classical nonlinear age-structured population model introduced by Gurtin \& MacCamy in the late 1970s. One of our main results expresses the global stability of the system in terms of the newborn function only. We also derive the existence of a threshold population size implying the population extinction, which is well-known in population dynamics as an Allee effect.
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| 2. |
- Asadzadeh, Mohammad, 1952, et al.
(författare)
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A posteriori error estimates for a coupled wave system with a local damping
- 2011
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Ingår i: Journal of Mathematical Sciences (JMS). - 1072-3374 .- 1573-8795. ; 174:3
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Tidskriftsartikel (refereegranskat)abstract
- We study a finite element method applied to a system of coupled wave equations in a bounded smooth domain in Rd, d = 1, 2, 3, associated with a locally distributed damping function. We start with a spatially continuous finite element formulation allowing jump discontinuities in time. This approach yields, L2(L2) and L∞(L2), a posteriori error estimates in terms of weighted residuals of the system. The proof of the a posteriori error estimates is based on the strong stability estimates for the corresponding adjoint equations. Optimal convergence rates are derived upon the maximal available regularity of the exact solution and justified through numerical examples.
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| 3. |
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| 4. |
- Asadzadeh, Mohammad, 1952, et al.
(författare)
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Convergence of Finite Volume Scheme for a Three-Dimensional Poisson Equation
- 2014
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Ingår i: Journal of Mathematical Sciences. - : Springer-Verlag New York. - 1072-3374 .- 1573-8795. ; 202:2, s. 130-153
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Tidskriftsartikel (refereegranskat)abstract
- We construct and analyze a finite volume scheme for numerical solution of a three-dimensional Poisson equation. We derive optimal convergence rates in the discrete H1 norm and sub-optimal convergence in the maximum norm, where we use the maximal available regularity of the exact solution and minimal smoothness requirement on the source term. The theoretical results are justified through implementing some canonical examples in 3D.
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| 5. |
- Beilina, Larisa, 1970, et al.
(författare)
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Adaptivity with relaxation for ill-posed problems and global convergence for a coefficient inverse problem
- 2010
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Ingår i: Journal of Mathematical Sciences, JMS, Springer. - : Springer Science and Business Media LLC. - 1072-3374 .- 1573-8795. ; 167:3, s. 279-325
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Tidskriftsartikel (refereegranskat)abstract
- A new framework of the functional analysis is developed for the finite element adaptive method (adaptivity) for the Tikhonov regularization functional for some ill-posed problems. As a result, the relaxation property for adaptive mesh refinements is established. An application to a multidimensional coefficient inverse problem for a hyperbolic equation is discussed. This problem arises in the inverse scattering of acoustic and electromagnetic waves. First, a globally convergent numerical method provides a good approximation for the correct solution of this problem. Next, this approximation is enhanced via the subsequent application of the adaptivity. Analytical results are verified computationally. Bibliography: 30 titles. Illustration: 2 figures.
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| 6. |
- Beilina, Larisa, 1970, et al.
(författare)
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New a posteriori error estimates for adaptivity technique and global convergence for a hyperbolic coefficient inverse problem
- 2011
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Ingår i: Journal of Mathematical Sciences. - : Springer Science and Business Media LLC. - 1573-8795 .- 1072-3374. ; 172:4, s. 449-476
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Tidskriftsartikel (refereegranskat)abstract
- The coefficient inverse problem for a hyperbolic equation is studied by using the two-stage numerical procedure consisting of the global convergence method and the adaptive finite element method. We obtain new a posteriori error estimates for the Lagrangian and for the unknown coefficient, which is important at the second stage of procedure from the computational point of view. The results are illustrated by numerical experiments. Bibliography: 23 titles. Illustrations: figures. © 2011 Springer Science+Business Media, Inc.
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| 7. |
- Berbyuk, Viktor, 1953, et al.
(författare)
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Effect of the deformability of structural links on the motion of a two-legged walking robot
- 1993
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Ingår i: Journal of Mathematical Sciences. - 1573-8795 .- 1072-3374. ; 65:6, s. 1991-1994
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Tidskriftsartikel (refereegranskat)abstract
- The problems of the dynamics and parametric optimization of the motion of a walking robot are solved within theframework of a seven-link robot's model with the elasticity of the structural components taken into account. The effect of the elasticity of the links on the kinematic, dynamic, and energy characteristics of the locomotion of the walking mechanism is studied.
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| 8. |
- Berbyuk, Viktor, 1953
(författare)
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The use of first integrals in the problem of optimal control of a linear system with a quadratic functional
- 1993
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Ingår i: Journal of Mathematical Sciences. - 1573-8795 .- 1072-3374. ; 63:1, s. 75-79
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Tidskriftsartikel (refereegranskat)abstract
- A method for constructing an optimal control of a linear system in a variational problem with fixed time for the control process, fixed endpoints of the phase trajectory, and a quadratic functional is proposed. The method is based on the use of first integrals of the equations of unperturbed motion. Sufficient conditions for complete controllability of the linear nonstationary system have been obtained.
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| 9. |
- Berbyuk, Viktor, 1953
(författare)
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The use of first integrals to synthesize the energetically optimal control of a nonlinear system
- 1997
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Ingår i: Journal of Mathematical Sciences. - 1573-8795 .- 1072-3374. ; 86:2, s. 2642-2645
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Tidskriftsartikel (refereegranskat)abstract
- In the paper a method of solving problems of optimal control of the motion of nonlinear dynamical systemswith respect to energy expenditure given a fixed time and fixed ends of the phase trajectory has been proposed. The method is based on the use of first integrals of the equations of free motion. The application of the method isillustrated by examples.
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| 10. |
- Berbyuk, Viktor, 1953
(författare)
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Weight-Vibration Pareto Optimization of a Dual Mass Flywheel
- 2022
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Ingår i: Journal of Mathematical Sciences. - : Springer Science and Business Media LLC. - 1573-8795 .- 1072-3374. ; 263:1, s. 1-14
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Tidskriftsartikel (refereegranskat)abstract
- By using the methodology of the multiobjective optimal design of engineering systems, we consider the problem of weight-vibration Pareto optimization of a dual mass flywheel with an aim to study the feasibility of its application in heavy-duty truck powertrains. The results obtained show the following: the solution of the considered optimization problem does exist; the mass inertia, stiffness, and damping parameters of the absorber optimized in an operating engine speed range of 600–2000 rpm exist and provide the best attenuation of the torque oscillation at the transmission input shaft. Finally, the obtained results show the feasibility evidence for the application of weight-vibration optimized dual mass flywheels in heavy-duty truck drivetrain systems.
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