124 research outputs found
Analysis of balance control methods based on inverted pendulum for legged robots
Methods of balance control for a legged robot, the model of which is presented as a two-section inverted pendulum, are considered. The following balance methods for humanoid robots are analysed: the parallel algorithm of the network operator method; the method of natural synergies; the method of fuzzy control, the spherical inverted pendulum mode, a dual length linear inverted pendulum method. The best of these methods will be used in the development of the Russian anthropomorphic robot Antares
The graceful exit from the anomaly-induced inflation: Supersymmetry as a key
The stable version of the anomaly-induced inflation does not need a fine
tuning and leads to sufficient expansion of the Universe. The non-stable
version (Starobinsky model) provides the graceful exit to the FRW phase. We
indicate the possibility of the inflation which is stable at the beginning and
unstable at the end. The effect is due to the soft supersymmetry breaking and
the decoupling of the massive sparticles at low energy.Comment: 10 pages, 2 figures using axodraw. Modified version. Discussion
concerning the gravitational scale modified, the effect of massive particles
in the last stage of inflation taken into accoun
DeWitt-Schwinger Renormalization and Vacuum Polarization in d Dimensions
Calculation of the vacuum polarization, , has seen a recent resurgence, notably
for black hole spacetimes. To date, most calculations of this type have been
done only in four dimensions. Extending these calculations to dimensions
includes -dimensional renormalization. Typically, the renormalizing terms
are found from Christensen's covariant point splitting method for the
DeWitt-Schwinger expansion. However, some manipulation is required to put the
correct terms into a form that is compatible with problems of the vacuum
polarization type. Here, after a review of the current state of affairs for
calculations and a thorough introduction to
the method of calculating and for certain spacetimes is discussed, with application to four and
five dimensions.Comment: 21 pages, 2 tables, 3 figures. References added, rewritten to clarify
some points, corrections performed, our claim in the first version that there
is an error in Anderson's calculations is incorrec
Анализ данных системы учета и автоматического регулирования теплоснабжения пяти- и более этажных жилых домов
The paper considers regulation of heat supply to housing buildings using automatic regulators. Integral index of automatic regulator action on the heat-supply system of multi-storey housing building is proportional to a thermal criterion of Pomerantsev similarity.Рассмотрено регулирование теплоснабжения жилых домов с использованием автоматических регуляторов. Интегральный показатель воздействия автоматического регулятора на систему теплоснабжения многоэтажного жилого дома оказывается пропорциональным теплофизическому критерию подобия Померанцева
Route to nonlocality and observation of accessible solitons
We develop a general theory of spatial solitons in a liquid crystalline
medium exhibiting a nonlinearity with an arbitrary degree of effective
nonlocality. The model accounts the observability of "accessible solitons" and
establishes an important link with parametric solitons.Comment: 4 pages, 2 figure
Manipulation and removal of defects in spontaneous optical patterns
Defects play an important role in a number of fields dealing with ordered
structures. They are often described in terms of their topology, mutual
interaction and their statistical characteristics. We demonstrate theoretically
and experimentally the possibility of an active manipulation and removal of
defects. We focus on the spontaneous formation of two-dimensional spatial
structures in a nonlinear optical system, a liquid crystal light valve under
single optical feedback. With increasing distance from threshold, the
spontaneously formed hexagonal pattern becomes disordered and contains several
defects. A scheme based on Fourier filtering allows us to remove defects and to
restore spatial order. Starting without control, the controlled area is
progressively expanded, such that defects are swept out of the active area.Comment: 4 pages, 4 figure
Quadratic solitons as nonlocal solitons
We show that quadratic solitons are equivalent to solitons of a nonlocal Kerr
medium. This provides new physical insight into the properties of quadratic
solitons, often believed to be equivalent to solitons of an effective saturable
Kerr medium. The nonlocal analogy also allows for novel analytical solutions
and the prediction of novel bound states of quadratic solitons.Comment: 4 pages, 3 figure
Dipole-Mode Vector Solitons
We find a new type of optical vector soliton that originates from trapping of
a dipole mode by a soliton-induced waveguide. These solitons, which appear as a
consequence of the vector nature of the two component system, are more stable
than the previously found optical vortex-mode solitons and represent a new type
of extremely robust nonlinear vector structure.Comment: Four pages with five eps figure
Quantum cosmology in the models of 2d and 4d dilatonic supergravity with WZ matter
We consider N=1 two-dimensional (2d) dilatonic supergravity (SG), 2d
dilatonic SG obtained by dimensional reduction from N=1 four-dimensional (4d)
SG, N=2 2d dilatonic SG and string-inspired 4d dilatonic SG. For all the
theories, the corresponding action on a bosonic background is constructed and
the interaction with (dilatonic) Wess-Zumino (WZ) multiplets is presented.
Working in the large-N approximation, it is enough to consider the trace
anomaly induced effective action due to dilaton-coupled conformal matter as a
quantum correction (for 2d models s-waves approximation is additionally used).
The equations of motion for all such models with quantum corrections are
written in a form convenient for numerical analysis. Their solutions are
numerically investigated for 2d and 4d Friedmann-Robertson-Walker (FRW) or 4d
Kantowski-Sacks Universes with a time-dependent dilaton via exponential dilaton
coupling. The evolution of the corresponding quantum cosmological models is
given for different choices of initial conditions and theory parameters. In
most cases we find quantum singular Universes. Nevertheless, there are examples
of Universe non-singular at early times. Hence, it looks unlikely that quantum
matter back reaction on dilatonic background (at least in large
approximation) may really help to solve the singularity problem.Comment: LaTeX file of the text (36 pages) and 3 ps files of 14 figures, few
misprints are corrected and references adde
Modulational instability of solitary waves in non-degenerate three-wave mixing: The role of phase symmetries
We show how the analytical approach of Zakharov and Rubenchik [Sov. Phys.
JETP {\bf 38}, 494 (1974)] to modulational instability (MI) of solitary waves
in the nonlinear Schr\"oedinger equation (NLS) can be generalised for models
with two phase symmetries. MI of three-wave parametric spatial solitons due to
group velocity dispersion (GVD) is investigated as a typical example of such
models. We reveal a new branch of neck instability, which dominates the usual
snake type MI found for normal GVD. The resultant nonlinear evolution is
thereby qualitatively different from cases with only a single phase symmetry.Comment: 4 pages with figure
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