Browsing by Author "Angelova J."

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    I-optimal curve for impulsive Lotka-Volterra predator-prey model
    (2002-05-01) Angelova J.; Dishliev A.; Nenov S.
    For the classical Lotka-Volterra predator-prey system, new notion I-optimal curve ξI is introduced. This curve is disposed in the phase space of the system. The curve ξI intersects each trajectory γc of Lotka-Volterra system at least once. The points of ξI possess the following optimal property: if (m, M) ∈ ξI ∩ γc(0), then after a ``jump`` with magnitude I to the origin of coordinates, it hits a trajectory γc(1) and c1 is minimal; i.e., γc(1) is the ``nearest`` to the stable centre. The minimality concerns the rest points of initial trajectory γc(0), from which the ``impulsive jumps`` (subtractings) with magnitude I to (0, 0) are realized. The monotonicity, continuity, and linear asymptotical behaviour of ξI curve are proved. © 2002 Elsevier Science Ltd. All rights reserved.
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    On the modified Reynolds equation for journal bearings in a case of non-Newtonian Rabinowitsch fluid model
    (2018-01-09) Javorova J.; Angelova J.
    In this paper, a theoretical analysis of hydrodynamic plain journal bearings with finite length at taking into account the effect of non-Newtonian lubricants is presented. Based upon the Rabinowitsch fluid model (cubic stress constitutive equation) and by integrating the continuity equation across the film, the nonlinear modified 2D Reynolds type equation is derived in details so that to study the dilatant and pseudoplastic nature of the lubricant in comparison with Newtonian fluid. A dimensionless equation of hydrodynamic pressure distribution in a form appropriate for numerical modeling is also presented. Some particular cases of 1D applications can be recovered from the present derivation.