Cálculo variacional e aplicações

This paper consists of a brief review and introduction to the main concepts of Classic Variational Calculus. Starting from thedefinitions of the concepts of first and second variation of a functional, we present a mathematically rigorous treatment for theVariational Calculus, establishing necessary and sufficient conditions for obtaining extrema. In this context, the notion of conjugatepoints is introduced, which is fundamental for the classification of weak extrema. Some simple and enlightening examples are dealtwith throughout the paper. Strong extrema are characterized and sufficient conditions for their occurrence are given. The paperconcludes with a brief application to Lagrange mechanics, showing the existence of actions whose stationary points are saddlepoints instead of minima.

Spherical Pendulum Small Oscillations for Slewing Crane Motion

The present paper focuses on the Lagrange mechanics-based description of small oscillations of a spherical pendulum with a uniformly rotating suspension center. The analytical solution of the natural frequencies’ problem has been derived for the case of uniform rotation of a crane boom. The payload paths have been found in the inertial reference frame fixed on earth and in the noninertial reference frame, which is connected with the rotating crane boom. The numerical amplitude-frequency characteristics of the relative payload motion have been found. The mechanical interpretation of the terms in Lagrange equations has been outlined. The analytical expression and numerical estimation for cable tension force have been proposed. The numerical computational results, which correlate very accurately with the experimental observations, have been shown.

Constant curvature coefficients and exact solutions in fractional gravity and geometric mechanics

We present a study of fractional configurations in gravity theories and Lagrange mechanics. The approach is based on a Caputo fractional derivative which gives zero for actions on constants. We elaborate fractional geometric models of physical interactions and we formulate a method of nonholonomic deformations to other types of fractional derivatives. The main result of this paper consists of a proof that, for corresponding classes of nonholonomic distributions, a large class of physical theories are modelled as nonholonomic manifolds with constant matrix curvature. This allows us to encode the fractional dynamics of interactions and constraints into the geometry of curve flows and solitonic hierarchies.

SUBALGEBRAS OF THE LIE ALGEBRA R6 AND THEIR APPLICATIONS

As we all know, the Hamiltonian systems are the same describing forms as Newton mechanics and Lagrange mechanics. Therefore, researching for a new Hamiltonian structure of the soliton equations has important significance. In the paper, firstly, with the help of the Lie algebra R6, a few types of subalgebras are constructed, from which the corresponding equivalent tensor systems are given. For their applications, two integrable couplings hierarchies along with the multi-potential component functions generated from the soliton theory and the Virasoro symmetric algebra are obtained. Secondly, the Hamiltonian structures of the above integrable couplings are worked out, which may become another describing expression for the Newton and Lagrange mechanics. In particular, one of the integrable couplings presented above reduces to the famous AKNS hierarchy of soliton equations.

Time-Integral Variational Principles for Nonlinear Nonholonomic Systems

This is a comprehensive treatment of the time-integral variational “principles” of mechanics for systems subject to general nonlinear and possibly nonholonomic velocity constraints (i.e., equations of the form f(t, q, q˙) = 0, where t = time and q/q˙ = Lagrangean coordinates/velocities), in general nonlinear nonholonomic coordinates. The discussion is based on the Maurer-Appell-Chetaev-Hamel definition of virtual displacements and subsequent formulation of the corresponding nonlinear transitivity (or transpositional) equations. Also, a detailed analysis of the latter supplies a hitherto missing clear geometrical interpretation of the well-known discrepancies between the equations of motion obtained by formal application of the calculus of variations (mathematics) and those obtained from the principle of d’Alembert-Lagrange (mechanics); i.e., admissible adjacent paths (mathematics) are locally nonvirtual; and adjacent paths built from locally virtual displacements (mechanics) are not admissible. (These discrepancies, although revealed about a century ago, for systems under Pfaffian constraints (Hertz (1894), Ho¨lder (1896), Hamel (1904), Maurer (1905), and others) seem to be relatively unknown and/or misunderstood among today’s engineers.) The discussion includes all relevant nonlinear nonholonomic variational principles, in both unconstrained and constrained forms of their integrands, and the corresponding nonlinear nonholonomic equations of motion. Such time-integral formulations are useful both conceptually and computationally (e.g., multibody dynamics).