1,243 research outputs found
Exact solutions for equilibrium configurations of charged conducting liquid jets
A wide class of exact solutions is obtained for the problem of finding the
equilibrium configurations of charged jets of a conducting liquid; these
configurations correspond to the finite-amplitude azimuthal deformations of the
surface of a round jet. A critical value of the linear electric charge density
is determined, for which the jet surface becomes self-intersecting, and the jet
splits into two. It exceeds the density value required for the excitation of
the linear azimuthal instability of the round jet. Hence, there exists a range
of linear charge density values, where our solutions may be stable with respect
to small azimuthal perturbations.Comment: 7 pages, 5 figures, to appear in Physical Review
A temperature behavior of the frustrated translational mode of adsorbate and the nature of the "adsorbate-substrate" interaction
A temperature behavior of the frustrated translational mode (T-mode) of a
light particle, coupled by different regimes of ohmicity to the surface, is
studied within a formalism of the generalized diffusion coefficients. The
memory effects of the adsorbate motion are considered to be the main reason of
the T-mode origin. Numerical calculations yield a thermally induced shift and
broadening of the T-mode, which is found to be linear in temperature for Ohmic
and super-Ohmic systems and nonlinear for strongly sub-Ohmic ones. We obtain
analytical expressions for the T-mode shift and width at weak coupling for the
systems with integer "ohmicity" indexes n=0-2 in zero temperature and high
temperature limits. We provide an explanation of the experimentally observed
blue- or red-shifts of the T-mode on the basis of a comparative analysis of two
typical times of the system evolution: a time of decay of the
"velocity-velocity" autocorrelation function, and a correlation time of the
thermal bath random forces. A relation of the T-mode to the multiple jumps of
the adsorbate is discussed, and generalization of conditions of the multiple
hopping to the case of quantum surface diffusion is performed.Comment: 12 pages, 4 figure
Dynamics of the Free Surface of a Conducting Liquid in a Near-Critical Electric Field
Near-critical behavior of the free surface of an ideally conducting liquid in
an external electric field is considered. Based on an analysis of three-wave
processes using the method of integral estimations, sufficient criteria for
hard instability of a planar surface are formulated. It is shown that the
higher-order nonlinearities do not saturate the instability, for which reason
the growth of disturbances has an explosive character.Comment: 19 page
Statistical Description of Hydrodynamic Processes in Ionic Melts with taking into account Polarization Effects
Statistical description of hydrodynamic processes for ionic melts is proposed
with taking into account polarization effects caused by the deformation of
external ionic shells. This description is carried out by means of the Zubarev
nonequilibrium statistical operator method, appropriate for investigations of
both strong and weak nonequilibrium processes. The nonequilibrium statistical
operator and the generalized hydrodynamic equations that take into account
polarization processes are received for ionic-polarization model of ionic
molten salts when the nonequilibrium averaged values of densities of ions
number, their momentum, dipole momentum and total energy are chosen for the
reduced description parameters. A spectrum of collective excitations is
investigated within the viscoelastic approximation for ion-polarization model
of ionic melts.Comment: 24 pages, RevTex4.1-format, no figure
Research of the possibility of self-excited vibrations amplitude reducing when turning by the variation of the cutting speed
In this paper the results of research of the possibilities of self-excited vibrations suppression in turning by the cutting speed modulation are presented. The experimental approach to conduct the variative control of lathe main drive is described. The possibilities of main drive working in continuous rotation speed mode are researched.В статье приведены результаты исследования возможности подавления автоколебаний при точении модулированием скоростью резания. Описан экспериментальный подход осуществления вариативного управления приводом главного движения токарного станка. Исследованы возможности привода главного движения работы в режиме постоянного варьирования скоростью вращения
Two-dimensional quantum spin-1/2 Heisenberg model with competing interactions
We study the quantum spin-1/2 Heisenberg model in two dimensions, interacting
through a nearest-neighbor antiferromagnetic exchange () and a ferromagnetic
dipolar-like interaction (), using double-time Green's function, decoupled
within the random phase approximation (RPA). We obtain the dependence of as a function of frustration parameter , where is the
ferromagnetic (F) transition temperature and is the ratio between the
strengths of the exchange and dipolar interaction (i.e., ). The
transition temperature between the F and paramagnetic phases decreases with
, as expected, but goes to zero at a finite value of this parameter,
namely . At T=0 (quantum phase transition), we
analyze the critical parameter for the general case of an
exchange interaction in the form , where ferromagnetic
and antiferromagnetic phases are present.Comment: 4 pages, 1 figur
Effects of Frustrated Surface in Heisenberg Thin Films
We study by extensive Monte Carlo (MC) simulations and analytical Green
function (GF) method effects of frustrated surfaces on the properties of thin
films made of stacked triangular layers of atoms bearing Heisenberg spins with
an Ising-like interaction anisotropy. We suppose that the in-plane surface
interaction can be antiferromagnetic or ferromagnetic while all other
interactions are ferromagnetic. We show that the ground-state spin
configuration is non linear when is lower than a critical value .
The film surfaces are then frustrated. In the frustrated case, there are two
phase transitions related to disorderings of surface and interior layers. There
is a good agreement between MC and GF results. In addition, we show from MC
histogram calculation that the value of the ratio of critical exponents
of the observed transitions is deviated from the values of two and
three Ising universality classes. The origin of this deviation is discussed
with general physical arguments.Comment: 9 pages, 16 figure
Growth and crystallization of molybdenum layers on amorphous silicon
The structure of molybdenum layers deposited by direct current magnetron sputtering onto the amorphous silicon (a-Si) layers as function of nominal layer thickness was studied by methods of transmission electron microscopy. Molybdenum layers with nominal thickness 1.5btMo nomb1.9 nm consist of clusters which should be considered as a transient state between strongly disordered (amorphous) state and crystal one. A transition from clusters to polycrystals takes place within the thickness range of 1.9btMo nomb2.5 nm. Resulting Mo crystallites have an inequiaxial form with dimensions of (3–4)×(15–30)nm2 and consist of blocks. The lateral axis of inequiaxial crystallites is parallel to 110 direction. As the metal layer thickness increases Mocrystallites take the more regular form at the expense of recrystallization
Self-consistent theory of turbulence
A new approach to the stochastic theory of turbulence is suggested. The
coloured noise that is present in the stochastic Navier-Stokes equation is
generated from the delta-correlated noise allowing us to avoid the nonlocal
field theory as it is the case in the conventional theory. A feed-back
mechanism is introduced in order to control the noise intensity.Comment: submitted to J.Tech. Phys.Letters (St. Petersburg
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