共查询到14条相似文献,搜索用时 15 毫秒
1.
S. S. Riaz S. Banarjee S. Kar D. S. Ray 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):509-515
We consider a reaction-diffusion system in crossed electric and magnetic fields lying on the reaction plane. It is shown that
a
charge separation along the direction normal to the reaction plane
resulting in a diffusional flux may cause a differential flow
induced chemical instability and stationary pattern formation on a
homogeneous steady state. This pattern is generically different from
a Turing pattern modified by the crossed fields. The special role of
magnetic field is emphasized. Our theoretical analysis is
corroborated by numerical simulation on a reaction-diffusion system
in three dimensions. 相似文献
2.
F. N. Si Q. X. Liu J. Z. Zhang L. Q. Zhou 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,60(4):507-513
It has been reported that traveling waves propagate
periodically and stably in sub-excitable systems driven by noise
[Phys. Rev. Lett. 88, 138301 (2002)]. As a further
investigation, here we observe different types of traveling waves
under different noises and periodic forces, using a simplified
Oregonator model. Depending on different noises and periodic forces,
we have observed different types of wave propagation (or their
disappearance). Moreover, reversal phenomena are observed in this
system based on the numerical experiments in the one-dimensional
space. We explain this as an effect of periodic forces. Thus, we
give qualitative explanations for how stable reversal phenomena
appear, which seem to arise from the mixing function of the periodic
force and the noise. The output period and three velocities (normal,
positive and negative) of the travelling waves are defined and their
relationship with the periodic forces, along with the types of
waves, are also studied in sub-excitable system under a fixed noise
intensity.
Electronic supplementary material Supplementary Online Material 相似文献
3.
The Eckhaus stability boundaries of travelling periodic roll patterns arising in binary fluid convection is analysed using high-resolution numerical methods. We present results corresponding to three different values of the separation ratio used in experiments. Our results show that the subcritical branches of travelling waves bifurcating at the onset of convection suffer sideband instabilities that are restabilised further away in the branch. If this restabilisation is produced after the turning point of the travelling-wave branch, these waves do not become stable in a saddle node bifurcation as would have been the case in a smaller domain. In the regions of instability of the uniform travelling waves we expect to find either transitions between states of different wave number or modulated travelling waves arising in these bifurcations. 相似文献
4.
P. Bot I. Mutabazi 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):141-155
The dynamics of defects in a pattern of traveling inclined rolls has been investigated. Two regimes were identified in the
neighborhood of defects: a diffusive regime, with a negative phase diffusion coefficient, and a coalescence regime in which
the phase gradient diverges in time following a power law behavior. The observed periodic nucleation of defects is related
to the frequency inhomogeneity induced by the disymmetry of the wave amplitude. Amplitude holes have been observed in the
secondary modulated pattern.
Received 23 February 1999 and Received in final form 26 May 1999 相似文献
5.
The role of thermodiffusive generation of concentration fluctuations via the Soret effect, their contribution to the buoyancy forces that drive convection, the advective mixing effect of the latter, and the diffusive homogenisation are compared and elucidated for oscillatory convection. Numerically obtained solutions of the field equations in the form of spatially extended relaxed traveling waves, of standing waves, and of the transient growth of standing waves and their transition to traveling waves are discussed as well as spatially localized convective states of traveling waves that are surrounded by the quiescent fluid. 相似文献
6.
E. Plaut L. Pastur R. Ribotta 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(2):283-297
We study experimentally the evolution of thermoconvection in a laterally extended planar nematic layer, at zero or weak stabilizing
magnetic field. As the applied thermal gradient is increased, a cascade of symmetry breakings occurs, towards structures of
increasing spatial complexity, and ultimately towards oscillating states. The patterns are characterized optically, and simple
models for the distortion of the vertical (out of plane) component of the director field are proposed.
Received: 1st December 1997 / Revised: 25 May 1998 / Accepted: 2 June 1998 相似文献
7.
The lifting Hele-Shaw cell (LHSC) is used to study adhesion as well as viscous fingering. In the present paper we report a
series of observations of development of the interface for different viscous fluids, both Newtonian and non-Newtonian, in
a LHSC operated at a constant lifting force. Glass and perspex are used as the plates in two different sets of experiments.
The objectives are 1) to measure the time required to separate the plates as a function of the lifting force and 2) to note
the force above which viscous fingering appears. We find that for the Newtonian fluids, the plate separation time follows
a universal power law with the lifting force, irrespective of fluid and substrate. The non-Newtonian fluids too, with proper
scaling obey the same power law. The appearance of fingering, however, depends on the properties of the fluid as well as the
substrate. We suggest a modified form of the capillary number which controls the onset of fingering; this new quantity, termed
the “fingering parameter” involves the dielectric constants of the substrate and fluid in addition to the viscosity and surface
tension. 相似文献
8.
We study the instability of a very thin liquid film resting on a uniformly stretched soft elastomeric substrate driven by
van der Waals forces. A linear stability analysis shows that the critical fluctuation wavelength in the tensile direction
is larger than those in the other directions. The magnitudes of the critical wavelengths are adjustable in the sense that
they depend on the principal stretch of the substrate. For example, when the principal stretch of the substrate varies from
1.0 (unstretched) to 3.0, the range of the critical wavelength in the tensile direction increases by 7.0% while that normal
to the tensile direction decreases by 8.7%. Therefore, the phenomenon may find potential applications in creating tunable
topographically patterned surfaces with nano-to microscale features. 相似文献
9.
L. Giuggioli Z. Kalay V. M. Kenkre 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(3):341-348
We study the transient dynamics of single species reaction diffusion systems whose reaction terms f(u) vary nonlinearly near
u ≈ 0, specifically as f(u) ≈ u2 and f(u) ≈ u3. We consider three cases, calculate
their traveling wave fronts and speeds analytically and solve the equations numerically with different initial conditions to study the approach to the asymptotic front shape
and speed. Observed time evolution is found to be
quite sensitive to initial conditions and to display in some cases nonmonotonic behavior, ascribable to the disparity in time
scales between the evolution of the front interior and the front tail. 相似文献
10.
R. D. Benguria M. C. Depassier M. Loss 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,61(3):331-334
We establish rigorous upper and lower bounds for the speed of pulled fronts with a cut-off. For all reaction terms of KPP
type a simple analytic upper bound is given. The lower bounds however depend on details of the reaction term. For a small
cut-off parameter the two leading order terms in the asymptotic expansion of the upper and lower bounds coincide and correspond
to the Brunet-Derrida formula. For large cut-off parameters the bounds do not coincide and permit a simple estimation of the
speed of the front. 相似文献
11.
T. M. Mishonov M. V. Stoev Y. G. Maneva 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,44(3):533-536
Absorption of Alfvén waves is considered to be the main mechanism of
heating in the solar corona. It is concluded that the sharp increase
of the plasma temperature by two orders of magnitude is related to a
self-induced opacity with respect to Alfvén waves. The maximal
frequency for propagation of Alfvén waves is determined by the
strongly temperature dependent kinematic viscosity. In such a way
the temperature jump is due to absorption of high frequency Alfvén
waves in a narrow layer above the solar surface. It is calculated
the power per unit area dissipated in this layer due to damping of
Alfvén waves that blows up the plasma and gives birth to the
solar wind. A model short wave-length (WKB) evaluation takes into
account the 1/f2 frequency dependence of the transversal magnetic
field and velocity spectral densities. Such spectral densities agree
with old magnetometric data taken by Voyager 1 and recent
theoretical calculations in the framework of Langevin-Burgers MHD.
The presented theory predicts existence of intensive high frequency
MHD Alfvén waves in the cold layer beneath the corona. It is
briefly discussed how this statement can be checked experimentally.
It is demonstrated that the magnitude of the Alfvén waves
generating random noise and the solar wind velocity can be expressed
only in terms of satellite experimental data. It is advocated that
investigation of properties of the solar surface as a random driver by
optical methods is an important task for future solar physics. 相似文献
12.
Dirk Helbing 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,67(3):345-356
A local agglomeration of cooperators can support the survival or spreading of cooperation, even when cooperation is predicted
to die out according to the replicator equation, which is often used in evolutionary game theory to study the spreading and
disappearance of strategies. In this paper, it is shown that success-driven motion can trigger such local agglomeration and
may, therefore, be used to supplement other mechanisms supporting cooperation, like reputation or punishment. Success-driven
motion is formulated here as a function of the game-theoretical payoffs. It can change the outcome and dynamics of spatial
games dramatically, in particular as it causes attractive or repulsive interaction forces. These forces act when the spatial
distributions of strategies are inhomogeneous. However, even when starting with homogeneous initial conditions, small perturbations
can trigger large inhomogeneities by a pattern-formation instability, when certain conditions are fulfilled. Here, these instability
conditions are studied for the prisoner’s dilemma and the snowdrift game. Furthermore, it is demonstrated that asymmetrical
diffusion can drive social, economic, and biological systems into the unstable regime, if these would be stable without diffusion. 相似文献
13.
R. L. Woulaché D. Yemélé T. C. Kofané 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,65(1):99-108
We investigate the effect of local inhomogeneity on the nucleation process of kink-antikink pairs in the driven nonlinear
Klein-Gordon model with the Remoissenet-Peyrard substrate potential, whose shape can be varied as a function of the shape
parameter and which has the sine-Gordon shape as a particular case. From numerical integrations of the model equations under
defined conditions, the configuration of the critical nucleus in the presence of a localized inhomogeneity is determined and
shown to be affected by the shape parameter of the substrate potential. The expression of the depinning threshold field of
kink-antikink pairs, which is the value of the applied field at which the process of the nucleation of kink-antikink pairs
takes place, is also obtained. The dependence of this depinning threshold field on the shape parameter r shows that it strongly increases, for small intensity of the impurity potential when the shape of the substrate potential
deviates from the sinusoidal one. 相似文献
14.
P. Berthault H. Desvaux 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,22(1):65-73
NMR of laser-polarized xenon is used to probe the dissolution behaviour of the noble gas in different liquids. The dissolution
and self-relaxation rates are extracted via a macroscopic model, and comparison of the decay rate of the xenon magnetization in deuterated and non-deuterated solvent
pairs allows the determination of the pure dipole-dipole contribution to relaxation. A transient convective effect, tentatively
assigned to the xenon concentration gradient, is observed and characterized by diffusion encoding MRI experiments. The flow
of xenon penetrates inside the solvent near the walls of the NMR tube, the longitudinal images showing a “” shape, the transverse ones a “O” shape. This convection effect has implications for delivery conditions of laser-polarized
xenon in continuous flow experiments and magnetic resonance imaging.
Received 29 April 2002 / Received in final form 26 July 2002 Published online 22 October 2002
RID="a"
ID="a"e-mail: hdesvaux@cea.fr
RID="b"
ID="b"URA CNRS/CEA 331 相似文献