72 research outputs found
Discrete Nonholonomic LL Systems on Lie Groups
This paper applies the recently developed theory of discrete nonholonomic
mechanics to the study of discrete nonholonomic left-invariant dynamics on Lie
groups. The theory is illustrated with the discrete versions of two classical
nonholonomic systems, the Suslov top and the Chaplygin sleigh. The preservation
of the reduced energy by the discrete flow is observed and the discrete
momentum conservation is discussed.Comment: 32 pages, 13 figure
Poisson structures for reduced non-holonomic systems
Borisov, Mamaev and Kilin have recently found certain Poisson structures with
respect to which the reduced and rescaled systems of certain non-holonomic
problems, involving rolling bodies without slipping, become Hamiltonian, the
Hamiltonian function being the reduced energy. We study further the algebraic
origin of these Poisson structures, showing that they are of rank two and
therefore the mentioned rescaling is not necessary. We show that they are
determined, up to a non-vanishing factor function, by the existence of a system
of first-order differential equations providing two integrals of motion. We
generalize the form of that Poisson structures and extend their domain of
definition. We apply the theory to the rolling disk, the Routh's sphere, the
ball rolling on a surface of revolution, and its special case of a ball rolling
inside a cylinder.Comment: 22 page
Nanoscale phase separation in films: evidence for the texture driven optical anisotropy
The IR optical absorption (0.1-1.5 eV) in the films
on LAO substrate exhibits the drastic temperature evolution of the spectral
weight evidencing the insulator to metal transition. Single crystal films were
found to reveal strong linear dichroism with anomalous spectral oscillations
and fairly weak temperature dependence. Starting from the concept of phase
separation, we develop the effective medium model to account for these effects.
The optical anisotropy of the films is attributed to the texturization of the
ellipsoidal inclusions of the quasimetal phase caused by a mismatch of the film
and substrate and the twin texture of the latter.Comment: 6 pages, 5 Encapsulated PostScript figures, uses RevTeX
The motion of the 2D hydrodynamic Chaplygin sleigh in the presence of circulation
We consider the motion of a planar rigid body in a potential flow with
circulation and subject to a certain nonholonomic constraint. This model is
related to the design of underwater vehicles.
The equations of motion admit a reduction to a 2-dimensional nonlinear
system, which is integrated explicitly. We show that the reduced system
comprises both asymptotic and periodic dynamics separated by a critical value
of the energy, and give a complete classification of types of the motion. Then
we describe the whole variety of the trajectories of the body on the plane.Comment: 25 pages, 7 figures. This article uses some introductory material
from arXiv:1109.321
Collisionless kinetic theory of rolling molecules
We derive a collisionless kinetic theory for an ensemble of molecules
undergoing nonholonomic rolling dynamics. We demonstrate that the existence of
nonholonomic constraints leads to problems in generalizing the standard methods
of statistical physics. In particular, we show that even though the energy of
the system is conserved, and the system is closed in the thermodynamic sense,
some fundamental features of statistical physics such as invariant measure do
not hold for such nonholonomic systems. Nevertheless, we are able to construct
a consistent kinetic theory using Hamilton's variational principle in
Lagrangian variables, by regarding the kinetic solution as being concentrated
on the constraint distribution. A cold fluid closure for the kinetic system is
also presented, along with a particular class of exact solutions of the kinetic
equations.Comment: Revised version; 31 pages, 1 figur
О подходе к созданию цифровой модели рельефа дна Арктического бассейна
In the report an approach to developing technology to create digital elevation models of the seabed using heterogeneous data is considered. The technology was tested on material hydrographic work carried out by domestic and foreign researchers in the Central Arctic Ocean with drifting ice, surface ships and submarines. The necessity of systematic analysis of different quality bathymetric information varying by level of reliability when creating common databases and digital models is justified.Описывается подход к разработке технологии создания цифровых моделей рельефа морского дна с использованием данных разнородных съемок. Технология апробирована на материалах гидрографических работ, выполненных отечественными и зарубежными исследователями в центральной части Северного Ледовитого океана с дрейфующего льда, с надводных и подводных носителей. Обоснована необходимость систематического анализа качества неравноточной батиметрической информации, полученной при маршрутных и площадных съемках и различающейся по уровню достоверности, при создании единых баз данных и цифровых моделей
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