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Search Results: 1 - 10 of 8010 matches for " Dan Comanescu "
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The Angular Momentum-Energy Space
Dan Comanescu
Physics , 2007,
Abstract: In this paper we shall define and study the angular momentum-energy space for the classical problem of plane-motions of a particle situated in a potential field of a central force. We shall present the angular momentum-energy space for some important cases.
The conservation of mass-moment parameters
Dan Comanescu
Physics , 2007,
Abstract: In this paper we study a concept of mass-moment parameter which is the generalization of the mass and the moments of inertia of a continuous media. We shall present some interesting kinematical results in the hypothesis that a set of mass-moment parameters are conserved in a motion of a continuous media.
An Adhesion Model for the Drag Force
Dan Comanescu
Physics , 2008,
Abstract: The paper present a model for the drag force between a resistive medium and a solid body using the hypothesis that the drag force is created by the adhesion of some particles of the resistive medium on the solid body's surface. The study focus on the mass evolution of the solid body.
Stability problem for the torque-free gyrostat by using algebraic methods
Dan Comanescu
Physics , 2011, DOI: 10.1016/j.aml.2012.02.035
Abstract: We apply an algebraic method for studying the stability with respect to a set of conserved quantities for the problem of torque-free gyrostat. If the conditions of this algebraic method are not fulfilled then the Lyapunov stability cannot be decided using the specified set of conserved quantities.
Stability of equilibrium states in the Zhukovski case of heavy gyrostat using algebraic methods
Dan Comanescu
Mathematics , 2011, DOI: 10.1002/mma.2595
Abstract: We study the stability of the equilibrium points of a skew product system. We analyze the possibility to construct a Lyapunov function using a set of conserved quantities and solving an algebraic system. We apply the theoretical results to study the stability of an equilibrium state of a heavy gyrostat in the Zhukovski case.
A note on stability of the vertical uniform rotations of the heavy top
Dan Comanescu
Mathematics , 2012, DOI: 10.1002/zamm.201200162
Abstract: We prove that the stability problem of a vertical uniform rotation of a heavy top is completely solved by using the linearization method and the conserved quantities of the differential system which describe the rotation of the heavy top.
A note on stability of nongeneric equilibria for an underwater vehicle
Petre Birtea,Dan Comanescu
Physics , 2014,
Abstract: We study the Lyapunov stability of a family of nongeneric equilibria with spin for underwater vehicles with noncoincident centers. The nongeneric equilibria belong to singular symplectic leaves that are not characterized as a preimage o a regular value of the Casimir functions. We find an invariant submanifold such that the nongeneric equilibria belong to a preimage of a regular value that involves sub-Casimir functions. We obtain results for nonlinear stability on this invariant submanifold.
Geometrical dissipation for dynamical systems
Petre Birtea,Dan Comanescu
Mathematics , 2011, DOI: 10.1007/s00220-012-1589-6
Abstract: On a Riemannian manifold $(M,g)$ we consider the $k+1$ functions $F_1,...,F_k,G$ and construct the vector fields that conserve $F_1,...,F_k$ and dissipate $G$ with a prescribed rate. We study the geometry of these vector fields and prove that they are of gradient type on regular leaves corresponding to $F_1,...,F_k$. By using these constructions we show that the cubic Morrison dissipation and the Landau-Lifschitz equation can be formulated in a unitary form.
The $ε$ - revised system with three linear controls
Dan Comanescu,Mihai Ivan,Gheorghe Ivan
Mathematics , 2006,
Abstract: In this paper we introduce the $\epsilon$ - revised system associated to a Hamilton - Poisson system. The $\epsilon$ - revised system of the rigid body with three linear controls is defined and some of its geometrical and dynamical properties are investigated.
Instability conditions for circulatory and gyroscopic conservative systems
Petre Birtea,Ioan Casu,Dan Comanescu
Mathematics , 2011, DOI: 10.1016/j.physd.2012.07.002
Abstract: We give a method which generates sufficient conditions for instability of equilibria for circulatory and gyroscopic conservative systems. The method is based on the Gramians of a set of vectors whose coordinates are powers of the roots of the characteristic polynomial for the studied systems. New instability results are obtained for general circulatory and gyroscopic conservative systems. We also apply this method for studying the instability of motion for a charged particle in a stationary electromagnetic field.
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