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1.
Dynamics of aeolian sand ripples 总被引:1,自引:0,他引:1
Z. Csahók C. Misbah F. Rioual A. Valance 《The European physical journal. E, Soft matter》2000,3(1):71-86
We analyze theoretically the dynamics of aeolian sand ripples. In order to put the study in the context, we first review existing
models. This paper is a continuation of two previous papers (Z. Csahók et al., Physica D 128, 87 (1999); A. Valance et al., Eur. Phys. J. B 10, 543 (1999)), the first one is based on symmetries and the second on a hydrodynamical model. We show how the hydrodynamical
model may be modified to recover the missing terms that are dictated by symmetries. The symmetry and conservation arguments
are powerful in that the form of the equation is model-independent. We then present an extensive numerical and analytical
analysis of the generic sand ripple equation. We find that at the initial stage the wavelength of the ripple is that corresponding
to the linearly most dangerous mode. At later stages the profile undergoes a coarsening process leading to a significant increase
of the wavelength. We find that including the next higher-order nonlinear term in the equation leads naturally to a saturation
of the local slope. We analyze both analytically and numerically the coarsening stage, in terms of a dynamical exponent for
the mean wavelength increase. We discuss some future lines of investigations.
Received 20 January 2000 相似文献
2.
Following our experimental observations of disclination lines in freely suspended droplets and free-standing films (Yu.A.
Nastishin et al., Eur. Phys. J. E 5 353 (2001)), topological defects of the twist grain boundary (TGBA) phase are considered according to two aspects: topological
and energetical. There are two classes of line defects, disclinations (as in the cholesteric (N*) phase and the liquid vortices phase (NL*), relating to the directors tripod symmetries) and dispirations (relating to the translation-rotation symmetries); there are no topological point defects. Differences between N*, NL* and
TGBA disclinations are physical, not topological. The absence of focal conic domains in the TGBA phase is an immediate consequence of the materialization of the helical axis
(along the χ-director); the same feature, coupled to the trend to parallelism of the smectic layers, accounts for the predominance
of λ-lines. Finally, the presence of defects akin to developable domains is explained in the frame of the leastcurvaturemodel, that requires the introduction of a third type of defects: the densitiesofedgedislocations of the smectic layers.
Received 20 February 2002 相似文献
3.
We reinterpret an instability in a two-dimensional free foam cluster previously discussed by Weaire et al. (Eur. Phys. J. E 7, 123 (2002)) in terms of the excess pressure in the bubbles. We conclude that in a free foam cluster no bubble can have a
pressure below that of the surrounding gas.
Received: 20 September 2002 / Accepted: 5 May 2003 / Published online: 27 May 2003
RID="a"
ID="a"e-mail: fatima.vaz@ist.utl.pt 相似文献
4.
Fukuda J 《The European physical journal. E, Soft matter》2007,24(1):91-98
It was shown experimentally (P.V. Dolganov et al., Europhys. Lett. 76, 250 (2006)) and by numerical calculations (C. Bohley, R. Stannarius, Eur. Phys. J. E 23, 25 (2007)) that the c -director profile of a two-dimensional chiral smectic-C (SmC) film around a circular inclusion adopts dipolar rather than
quadrupolar configuration observed in achiral SmC films. We give an analytical argument on how spontaneous bend inherent in
chiral SmC liquid crystals influences the configuration of a SmC liquid crystal film around a circular inclusion imposing
tangential anchoring. We find how the angle α between two surface defects seen from the center of the inclusion depends on
the radius of the inclusion R and the strength of the spontaneous bend q . We show, however, that the contribution of the spontaneous bend to the free energy suffers from mathematical ambiguity;
it depends on the mathematical treatment of the outer boundary even when it is at infinity. This might indicate that the shape
as well as the treatment of the outer boundary of the film can significantly influence the equilibrium configuration of the
c -director and the position of the surface defects. 相似文献
5.
Dong Shu-bao Feng Er-yin Huang Wu-ying Cui Zhi-feng 《Czechoslovak Journal of Physics》2005,55(1):27-33
Molecular reaction dynamics of Cl + H2 (D2) has been studied on the latest analytical potential energy surface called BW3 using the Monte Carlo quasi-classical trajectory method. Excitation functions, differential cross sections and angular distributions of HCl and DCl products have been calculated. The excitation functions of the Cl (2P3/2) + n-H2 and Cl(2P3/2) + n-D2 reactions are also studied. The results are compared with those of quasi-classical trajectory [M. Alagia et al.: Phys. Chem. Chem. Phys. 2 (2000); F. J. Aoiz et al.: J. Phys. Chem. 100 (1996)], quantum mechanical (QM) calculations [F. J. Aoiz et al.:J. Chem. Phys. 115 (2001)] and experimental data [S. H. Lee et al.: J. Chem. Phys. 110 (1999); F. Dong et al.: J. Chem. Phys. 115 (2001)]. Discussions are given to some new results. 相似文献
6.
We discuss the interrelations between symmetry of an Ito stochastic differential equations (or systems thereof) and its integrability, extending in party results by R. Kozlov [J. Phys. A 43 (2010) & 44 (2011)]. Together with integrability, we also consider the relations between symmetries and reducibility of a system of SDEs to a lower dimensional one. We consider both “deterministic” symmetries and “random” ones, in the sense introduced recently by Gaeta and Spadaro [J. Math. Phys. 58 (2017)]. 相似文献
7.
A. Casado T. Marshall R. Risco-Delgado E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2001,13(1):109-119
We continue the study of parametric down conversion within the framework of the Wigner representation, by using a Maxwellian
approach developed in a recent paper [A. Casado et al., Eur. Phys. J. D 11, 465 (2000)]. This gives a mechanism, inside the crystal, for the production of the down-converted radiation. We obtain the
electric field to second order in the coupling constant by using the Green's function method, and compare our treatment with
the standard Hamiltonian approach. The spectrum of the down-converted radiation is calculated as a function of the parameters
of the nonlinear crystal (in particular the length) and the radius of the pumping beam.
Received 15 May 2000 相似文献
8.
J.S. H?ye I. Brevik 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,64(1):1-3
The Casimir friction problem can be dealt with in a simplified way by considering two
harmonic oscillators moving with constant relative velocity. Recently we calculated the
energy dissipation ΔE for such a case [Europhys. Lett. 91,
60003 (2010); Eur. Phys. J. D 61, 335 (2011)]. A recent study of Barton [New
J. Phys. 12, 113044 (2010)] seemingly leads to a different result for the
dissipation. If such a discrepancy really were true, it would imply a delicate difficulty
for the basic theory of Casimir friction. In the present note we show that the expressions
for ΔE are in fact physically equivalent, at
T = 0. 相似文献
9.
E. Santos 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(3):531-536
A recent experiment by Brida et al. [Eur. Phys. J. D 44, 547 (2007)] is analyzed with the conclusion that the results disagree with standard quantum predictions but fit a simple
local hidden variables model. New experiments are proposed which might throw new light on the anomaly. 相似文献
10.
Tomar G Shankar V Shukla SK Sharma A Biswas G 《The European physical journal. E, Soft matter》2006,20(2):185-200
The instability, rupture, and subsequent growth of holes in a thin Jeffreys-type viscoelastic film under the influence of
long-range van der Waals force are investigated using both linear stability analysis and nonlinear numerical solutions. The
linear stability analysis of full governing equations valid for arbitrary wave numbers shows that although fluid rheology
does not influence the dominant length scale of the instability, it significantly affects the growth rate. It is shown that
neglect of inertia and solvent dynamics results in a nonphysical singularity in the growth rate beyond a critical value of
relaxation time. We further carry out numerical simulations of a set of long-wave, nonlinear differential equations (also
derived in Rauscher et al., Eur. Phys. J. E 17, 373 (2005)) governing the evolution of the free surface. The nonlinear simulations, in their domain of validity, confirm
the results of the linear analysis. Interestingly, results from nonlinear simulations further show that both for Newtonian
and viscoelastic liquids, the shape and the dewetting dynamics of a hole are identical when examined in terms of a rescaled
time which depends on rheological parameters. Thus, viscoelasticity of Jeffreys type merely accelerates the growth rate, without
however affecting the important morphological characteristics. 相似文献
11.
N. Destainville 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,52(1):119-123
We perform Transition matrix Monte Carlo simulations to evaluate the
entropy of rhombus tilings with fixed polygonal boundaries and
2D-fold rotational symmetry. We estimate the large-size limit of
this entropy for D=4 to 10. We confirm analytic predictions of
[N. Destainville et al., J. Stat. Phys. 120, 799
(2005) and M. Widom et al., J. Stat. Phys. 120, 837
(2005)], in particular that the large size and large D limits
commute, and that entropy becomes insensible to size, phason strain
and boundary conditions at large D. We are able to infer finite
D and finite size scalings of entropy. We also show that
phason elastic constants can be estimated for any D by measuring the
relevant perpendicular space fluctuations. 相似文献
12.
A. Faggionato D. Gabrielli M. Ribezzi Crivellari 《Journal of statistical physics》2009,137(2):259-304
We consider a class of stochastic dynamical systems, called piecewise deterministic Markov processes, with states (x,σ)∈Ω×Γ, Ω being a region in ℝ
d
or the d-dimensional torus, Γ being a finite set. The continuous variable x follows a piecewise deterministic dynamics, the discrete variable σ evolves by a stochastic jump dynamics and the two resulting evolutions are fully-coupled. We study stationarity, reversibility
and time-reversal symmetries of the process. Increasing the frequency of the σ-jumps, the system behaves asymptotically as deterministic and we investigate the structure of its fluctuations (i.e. deviations
from the asymptotic behavior), recovering in a non Markovian frame results obtained by Bertini et al. (Phys. Rev. Lett. 87(4):040601,
2001; J. Stat. Phys. 107(3–4):635–675, 2002; J. Stat. Mech. P07014, 2007; Preprint available online at , 2008), in the context of Markovian stochastic interacting particle systems. Finally, we discuss a Gallavotti–Cohen-type symmetry
relation with involution map different from time-reversal. 相似文献
13.
D. Merten U. Löring K. Kretzschmar B. Metsch H.-R. Petry 《The European Physical Journal A - Hadrons and Nuclei》2002,14(4):477-489
We compute electroweak form factors of the nucleon and photon transition form factors of non-strange baryon resonances up
to the third resonance region in a model with instanton-induced interaction. The calculation is based on the Bethe-Salpeter
equation for three light constituent quarks and is fully relativistic (U. L?ring et al., Eur. Phys. J. A 10, 309 (2001)). Static nucleon properties and photon resonance couplings are in good agreement with experiment and the Q2 behaviour of the experimentally known form factors up to large momentum transfer is accounted for.
Received: 4 April 2002 / Accepted: 2 May 2002 相似文献
14.
E.P. Borges 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(4):593-595
Comment on Eur. Phys. J. B 27, 445 (2002)
We analyze the distribution of success of musicians, comparing a stretched exponential (found by J.A. Davies [Eur. Phys.
J. B 27, 445 (2002)]) with a distribution of the family of the q-exponential (presenting an intermediate power-law regime with a crossover to an exponential tail). We find that both assumptions
yield comparable results, within the available range of data, hence a definite conclusion cannot yet be taken. But this example
joins many others that has been found to be fairly described by q-exponentials (or variations of it), which may be indicative that there is a (significantly large) class of systems described
by nonextensive statistical mechanics, from where q-exponentials naturally appear.
Received 17 October 2002 Published online 31 December 2002 相似文献
15.
We previously observed that an intrinsic staking fault shrunk through a glide of a Shockley partial dislocation terminating its lower end in a hard-sphere crystal under gravity coherently grown in ?001? by Monte Carlo simulations [Mori et al., Molec. Phys. 105, 1377 (2007)]; it was an answer to a one-decade long standing question why the stacking disorder in colloidal crystals reduced under gravity [Zhu et al., Nature 387, 883 (1997)]. Here, we present an elastic energy calculation; in addition to the self-energy of the partial dislocation [Mori et al., Prog. Theor. Phys. Suppl. 178, 33 (2009)] we calculate the cross-coupling term between elastic field due to gravity and that due to a Shockley partial dislocation. The cross-term is an increasing function of the linear dimension R over which the elastic field expands, showing that a driving force arises for the partial dislocation moving toward the upper boundary of a grain. 相似文献
16.
G. Q. Zhang U. Tirnakli L. Wang T. L. Chen 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,82(1):83-89
A modified version of the Olami-Feder-Christensen model
has been introduced to consider avalanche size differences. Our
model well demonstrates the power-law behavior and finite size
scaling of avalanche size distribution in any range of the adding
parameter p
a
d
d
of the model. The probability density
functions of the avalanche size differences at consecutive
time steps (defined as returns) appear to be well approached, in
the thermodynamic limit, by q-Gaussian shape with appropriate
q values which can be obtained a priori from the avalanche size
exponent τ. For small system sizes, however, return
distributions are found to be consistent with the crossover
formulas proposed recently in Tsallis and Tirnakli [J. Phys.
Conf. Ser. 201, 012001 (2010)]. Our results strengthen
recent findings of Caruso et al. [Phys. Rev. E
75, 055101(R) (2007)] on the real earthquake data
which support the hypothesis that knowing the magnitude of
previous earthquakes does not make the magnitude of the next
earthquake predictable. 相似文献
17.
In the context of molecular dynamics simulations of rare events, the application of constraints on a suitable reaction coordinate has often been found useful for sampling of the free energy barrier. The efficiency of these calculations is hampered by geometrical difficulties, related to the metric factor and inertial forces. Some years ago Mulders et al. [1996, J. chem. Phys., 104, 48691 suggested a way to simplify the approach. Their idea was demonstrated shortly afterwards by Sprik and Ciccotti [1998, J. chem. Phys., 109, 77371. The present paper extends these results to vector reaction coordinate and molecular systems modelled with holonomic constraints. 相似文献
18.
J.E. Lorenzo H. Requardt 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(2):185-186
Eur. Phys. J. B 24, 315 (2001) Here we comment on a recently published paper on the presence of a phason contribution in the low temperature heat capacity data of the charge-density-wave compounds K0.3MoO3 and (TaSe4)2I. We have shown that the anomaly in the C
P
/
T
3
data reported by Odin et al. is straightforwardly interpreted in terms of low energy phonon modes resulting from the peculiar topology of these compounds.
Received 21 February 2002 Published online 19 July 2002 相似文献
19.
V. A. Bernshtam Yu. Ralchenko Y. Maron 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,51(3):319-320
We show that the criticism [Eur. Phys. J. D 49, 167 (2008)] of our
empirical formula for electron-impact ionization of atomic ions [J. Phys B. 33, 5025 (2000)] is unjustified. 相似文献
20.
B. H. Yanga P. C. Stancil 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,49(3):317-324
Quantum close-coupling and coupled-state approximation scattering calculations for rotational energy transfer of rotationally
excited CH4 due to collisions with He are presented for collision energies between 10−7 and 3000 cm−1 using the MP4 potential of Calderoni et al. [J. Chem. Phys. 121, 8261 (2004)]. State-to-state cross sections and rate coefficients
from selected initial rotational states of CH4 in symmetries A, E, and F are studied from the ultra-cold to the thermal regime. Comparison of the cross sections with available theoretical results
and experimental data show good agreement. Applications to astrophysics and cold laboratory environments are briefly addressed. 相似文献