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This paper focuses on studying Lie symmetries and conserved quantities of discrete nonholonomic Hamiltonian systems. Firstly, the discrete generalized Hamiltonian canonical equations and discrete energy equation of nonholonomic Hamiltonian systems are derived from discrete Hamiltonian action. Secondly, the determining equations and structure equation of Lie symmetry of the system are obtained. Thirdly, the Lie theorems and the conservation quantities are given for the discrete nonholonomic Hamiltonian systems. Finally, an example is discussed to illustrate the application of the results. 相似文献
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A discrete total variation calculus with variable time steps is
presented for mechanico-electrical systems where there exist
non-potential and dissipative forces. By using this discrete
variation calculus, the symplectic-energy-first integrators for
mechanico-electrical systems are derived. To do this, the time step
adaptation is employed. The discrete variational principle and the
Euler--Lagrange equation are derived for the systems. By using this
discrete algorithm it is shown that mechanico-electrical systems are
not symplectic and their energies are not conserved unless they are
Lagrange mechanico-electrical systems. A practical example is
presented to illustrate these results. 相似文献
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Symmetries and conserved quantities of discrete wave equation associated with the Ablowitz-Ladik-Lattice system
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In this paper, we present a new method to obtain the Lie symmetries and conserved quantities of the discrete wave equation with the Ablowitz-Ladik-Lattice equations. Firstly, the wave equation is transformed into a simple difference equation with the Ablowitz-Ladik-Lattice method. Secondly, according to the invariance of the discrete wave equation and the Ablowitz-Ladik-Lattice equations under infinitesimal transformation of dependent and independent variables, we derive the discrete determining equation and the discrete restricted equations. Thirdly, a series of the discrete analogs of conserved quantities, the discrete analogs of Lie groups, and the characteristic equations are obtained for the wave equation. Finally, we study a model of a biological macromolecule chain of mechanical behaviors, the Lie symmetry theory of discrete wave equation with the Ablowitz-Ladik-Lattice method is verified. 相似文献
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