arXiv
(422,153 recursos)
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Mostrando recursos 21 - 40 de 13,166
21.
Generation of spin-wave dark solitons with phase engineering - Bischof, Bengt; Slavin, Andrei N.; Benner, Hartmut; Kivshar, Yuri
We generate experimentally spin-wave envelope dark solitons from rectangular
high-frequency dark input pulses with externally introduced phase shifts in
yttrium-iron garnet magnetic fims. We observe the generation of both odd and
even numbers of magnetic dark solitons when the external phase shift varies.
The experimental results are in a good qualitative agreement with the theory of
the dark-soliton generation in magnetic films developed earlier [Phys. Rev.
Lett. 82, 2583 (1999)].
22.
A new integrable 3+1 dimensional generalization of the Burgers equation - Rudnev, M.; Yurov, A. V.; Yurov, V. A.
A new nonlinear 3+1 dimensional evolution equation admitting the Lax pair is
presented. In the case of one spatial dimension, the equation reduces to the
Burgers equation. A method of construction of exact solutions, based on a class
of discrete symmetries of the former equation is developed. These symmetries
reduce to the Cole-Hopf transformation in one-dimensional limit. Some exact
solutions are analyzed, in the physical context of spatial dissipative
structures and shock wave dressing.
23.
Anomalous scaling of low-order structure functions of turbulent velocity - Chen, S. Y.; Dhruva, B.; Kurien, S.; Sreenivasan, K. R.; Taylor, M. A.
It is now believed that the scaling exponents of moments of velocity
increments are anomalous, or that the departures from Kolmogorov's (1941)
self-similar scaling increase nonlinearly with the increasing order of the
moment. This appears to be true whether one considers velocity increments
themselves or their absolute values. However, moments of order lower than 2 of
the absolute values of velocity increments have not been investigated
thoroughly for anomaly. Here, we discuss the importance of the scaling of
non-integer moments of order between +2 and -1, and obtain them from direct
numerical simulations at moderate Reynolds numbers (Taylor microscale Reynolds
numbers $R_\lambda \le$ 450) and experimental data at high...
24.
Observation of stable phase jump lines in convection of a twisted nematic - Tatsumi, Soichi; Rossberg, A. G.; Sano, Masaki
We report observations of stable, localized, line-like structures in the
spatially periodic pattern formed by nematic electroconvection, along which the
phase of the pattern jumps by $\pi$. With increasing electric voltage, these
lines form a grid-like structure that goes over into a structure
indistinguishable from the well known grid pattern. We present theoretical
arguments that suggest that the twisted cell geometry we are using is
indirectly stabilizing the phase jump lines, and that the PJL lattice is caused
by an interaction of phase jump lines and a zig-zag instability of the
surrounding pattern.
25.
Critical exponents of Nikolaevskii turbulence - Tanaka, Dan
We study the spatial power spectra of Nikolaevskii turbulence in
one-dimensional space. First, we show that the energy distribution in
wavenumber space is extensive in nature. Then, we demonstrate that, when
varying a particular parameter, the spectrum becomes qualitatively
indistinguishable from that of Kuramoto-Sivashinsky turbulence. Next, we derive
the critical exponents of turbulent fluctuations. Finally, we argue that in
some previous studies, parameter values for which this type of turbulence does
not appear were mistakenly considered, and we resolve inconsistencies obtained
in previous studies.
26.
Hodograph transformations for a Camassa- Holm hierarchy in 2+1 dimensions - Estevez, P. G.; Prada, J.
A generalization of the negative Camassa-Holm hierarchy to 2+1 dimensions is
presented under the name CHH(2+1). Several hodograph transformations are
applied in order to transform the hierarchy into a system of coupled CBS
(Calogero-Bogoyavlenskii-Schiff) equations in 2+1 dimensions that pass the
Painleve test. A non-isospectral Lax pair for CHH(2+1) is obtained through the
above mentioned relationship with the CBS spectral problem..
27.
Singular manifold method for an equation in 2+1 dimensions - Estevez, P. G.; Prada, J.
he Singular Manifold Method is presented as an excellent tool to study a 2+1
dimensional equation in despite of the fact that the same method presents
several problems when applied to 1+1 reductions of the same equation.
Nevertheless these problems are solved when the number of dimensions of the
equation is increased.
28.
Large-scale energy spectra in surface quasi-geostrophic turbulence - Tran, Chuong V.; Bowman, John C.
The large-scale energy spectrum in two-dimensional turbulence governed by the
surface quasi-geostrophic (SQG) equation
$$\partial_t(-\Delta)^{1/2}\psi+J(\psi,(-\Delta)^{1/2}\psi) =\mu\Delta\psi+f$$
is studied. The nonlinear transfer of this system conserves the two quadratic
quantities $\Psi_1=<[(-\Delta)^{1/4}\psi]^2>/2$ and
$\Psi_2=<[(-\Delta)^{1/2}\psi]^2>/2$ (kinetic energy), where $<\cdot>$ denotes
a spatial average. The energy density $\Psi_2$ is bounded and its spectrum
$\Psi_2(k)$ is shallower than $k^{-1}$ in the inverse-transfer range. For
bounded turbulence, $\Psi_2(k)$ in the low-wavenumber region can be bounded by
$Ck$ where $C$ is a constant independent of $k$ but dependent on the domain
size. Results from numerical simulations confirming the theoretical predictions
are presented.
29.
Remarks on the KLB theory of two-dimensional turbulence - Tran, Chuong V.; Shepherd, Theodore G.
We study the inverse energy transfer in forced two-dimensional (2D)
Navier--Stokes turbulence in a doubly periodic domain. It is shown that an
inverse energy cascade that carries a nonzero fraction of the injected energy
to the large scales via a power-law energy spectrum $\propto k^{-\alpha}$
requires that $\alpha\ge5/3$. This result is consistent with the classical
theory of 2D turbulence that predicts a $k^{-5/3}$ inverse-cascading range,
thus providing for the first time a rigorous basis for this important feature
of the theory. We derive bounds for the Kolmogorov constant $C$ in the
classical energy spectrum $E(k)=C\epsilon^{2/3}k^{-5/3}$, where $\epsilon$ is
the energy injection rate. Issues related to Kraichnan's conjecture of energy
condensation...
30.
On chaotic behavior of gravitating stellar shells - Barkov, M. V.; Bisnovatyi-Kogan, G. S.; Neishtadt, A. I.; Belinski, V. A.
Motion of two gravitating spherical stellar shells around a massive central
body is considered. Each shell consists of point particles with the same
specific angular momenta and energies. In the case when one can neglect the
influence of gravitation of one ("light") shell onto another ("heavy") shell
("restricted problem") the structure of the phase space is described. The
scaling laws for the measure of the domain of chaotic motion and for the
minimal energy of the light shell sufficient for its escape to infinity are
obtained.
31.
Dynamical Properties of nystagmus - Vitanov, Nikolay K.; Todorova, Veneta
By the methods of the time series analysis we investigate human vestibular
and optovestibular nystagmus time series. They can be stationary or
nonstationary and are between the classes of purely periodic or purely chaotic
time series. The amplitudes of the autocorrelation functions of the time series
have an unexpected peak between 7 and 9 seconds on the time axis. The singular
spectrum analysis shows that the important information about the time series is
concentrated in the first four to six principal components. The influence of
the sensory input modality, which can be changed by opening or closing eyes of
the investigated persons, leads to changes in the histogram,...
33.
Two-Ion Dusty Plasma Waves and Landau Damping - Atamaniuk, B.; Zuchowski, K.
The paper analyses the properties of dusty plasmas in the extreme conditions
when the free electrons are absent. The nonlinear Korteveg de Vries equation
with a nonlocal (integral) term in a small parameter approximation is derived.
The conditions are determined when the integral term is essential hence the
Landau damping of two-ion-dusty plasma waves is substantial.
34.
The classical dynamics of two-electron atoms near the triple collision - Lee, Min-Ho; Tanner, Gregor; Choi, Nark Nyul
The classical dynamics of two electrons in the Coulomb potential of an
attractive nucleus is chaotic in large parts of the high-dimensional phase
space. Quantum spectra of two-electron atoms, however, exhibit structures which
clearly hint at the existence of approximate symmetries in this system. In a
recent paper,(Phys. Rev. Lett. 93, 054302 (2004)), we presented a study of the
dynamics near the triple collision as a first step towards uncovering the
hidden regularity in the classical dynamics of two electron atoms. The
non-regularisable triple collision singularity is a main source of chaos in
three body Coulomb problems. Here, we will give a more detailed account of our
findings based...
35.
On integration of the Kowalevski gyrostat and the Clebsch problems - Komarov, I V; Tsiganov, A V
For the Kowalevski gyrostat change of variables similar to that of the
Kowalevski top is done. We establish one to one correspondence between the
Kowalevski gyrostat and the Clebsch system and demonstrate that Kowalevski
variables for the gyrostat practically coincide with elliptic coordinates on
sphere for the Clebsch case. Equivalence of considered integrable systems
allows to construct two Lax matrices for the gyrostat using known rational and
elliptic Lax matrices for the Clebsch model. Associated with these matrices
solutions of the Clebsch system and, therefore, of the Kowalevski gyrostat
problem are discussed. The Kotter solution of the Clebsch system in modern
notation is presented in detail.
36.
Innovation as Evolution: Case Study Phylomemetic of Cellphone Designs - Khanafiah, Deni; Situngkir, Hokky
Cellular phone is one of the most developing technological artifacts today.
The evolution occurs through random innovation. Our effort is trying to view
the evolution of this artifact from memetics. By constructing a phylomemetic
tree based on cellular phone memes to infer or estimate the evolutionary
history and relationship among cellular phone. We adopt several methods, which
are commonly used in constructing phylogenetic tree, they are UPGMA algorithm
and Parsimony Maximum algorithm to construct cellphone phylomemetic tree.
Therefore we compare with the innovation tree, which is based on serial number
and their appearance time. From phylomemetic tree, we then analyze the process
of a cellular phone innovation through looking...
37.
On application of fractal analysis to cranial sutures - Gorski, Andrzej Z.; Skrzat, Janusz
Fractal exponents ($d$) for human cranial sutures are calculated using the
box counting method. The results were found around $d = 1.5$ (within the range
$1.3\div 1.7$), supporting the random walk model for the suture formation
process. However, the calculated dispersion above the estimated accuracy
suggests that other mechanisms are also present. Similar numbers were obtained
for both the sagittal and coronal sutures, with the coronal sutures displaying
a better scaling. Our results are compared with estimations published by other
authors.
38.
Parameter mismatch estimation using large deviations from synchronization - Bagaipo, Jupiter; Restrepo, Juan G.
We present a method to determine the relative parameter mismatch in a
collection of nearly identical chaotic oscillators by measuring large
deviations from the synchronized state. We demonstrate our method with an
ensemble of slightly different circle maps. We discuss how to apply our method
when there is noise, and show an example where the noise intensity is
comparable to the mismatch.
39.
The Boussinesq equation and Miura type transformations - Pavlov, Maxim
A direct method for calculation of Miura type transformations via LA pair is
used for the Boussinesq equation. Quadratic Miura type transformations
connected with local weakly-nonlocal (Maltsev-Novikov) Hamiltonian structures.
Modified systems are presented.
40.
Explicit integration of the H\'enon-Heiles Hamiltonians - Conte, Robert; Musette, Micheline; Verhoeven, Caroline
We consider the cubic and quartic He'non-Heiles Hamiltonians with additional
inverse square terms, which pass the Painleve' test for only seven sets of
coefficients. For all the not yet integrated cases we prove the
singlevaluedness of the general solution. The seven Hamiltonians enjoy two
properties: meromorphy of the general solution, which is hyperelliptic with
genus two and completeness in the Painleve' sense (impossibility to add any
term to the Hamiltonian without destroying the Painleve' property).
21.
