11,987 research outputs found
On the existence of chaotic circumferential waves in spinning disks
We use a third-order perturbation theory and Melnikov's method to prove the
existence of chaos in spinning circular disks subject to a lateral point load.
We show that the emergence of transverse homoclinic and heteroclinic points
respectively lead to a random reversal in the traveling direction of
circumferential waves and a random phase shift of magnitude for both
forward and backward wave components. These long-term phenomena occur in
imperfect low-speed disks sufficiently far from fundamental resonances.Comment: 8 pages, 5 figures, to appear in CHAOS (Volume 17, Issue 2, June
2007
Battery Lifetime Extension Using Super capacitors in Small-Scale Wind-Energy System with fuzzy logic control
Because of the variable attributes of renewable era, batteries utilized as a part of renewable-force frameworks can experience numerous unpredictable, incomplete charge/release cycles. This study shows a technique for enhancing battery lifetime in a little scale remote-zone wind-power framework by the utilization of a battery/super capacitor half breed vitality stockpiling framework. An agent element model of the general framework, consolidating practical wind-speed and load power varieties has been produced
Neutral Larkin--Ovchinnikov--Fulde--Ferrell state and chromomagnetic instability in two-flavor dense QCD
In two-flavor dense quark matter, we describe the dynamics in the single
plane wave Larkin--Ovchinnikov--Fulde--Ferrell (LOFF) state satisfying the
color and electric neutrality conditions. We find that because the neutral LOFF
state itself suffers from a chromomagnetic instability in the whole region
where it coexists with the (gapped/gapless) two-flavor superconducting
(2SC/g2SC) phases, it cannot cure this instability in those phases. This is
unlike the recently revealed gluonic phase which seems to be able to resolve
this problem.Comment: Revtex4, 5 pages, 3 figures, clarifications added, to appear in
Phys.Rev.Let
Spin-lattice coupling mediated giant magnetodielectricity across the spin reorientation in Ca2FeCoO5
The structural, phonon, magnetic, dielectric, and magneto dielectric
responses of the pure bulk Brownmillerite compound Ca2FeCoO5 are reported. This
compound showed giant magneto dielectric response (10%-24%) induced by strong
spin-lattice coupling across its spin reorientation transition (150-250 K). The
role of two Debye temperatures pertaining to differently coordinated sites in
the dielectric relaxations is established. The positive giant
magneto-dielectricity is shown to be a direct consequence of the modulations in
the lattice degrees of freedom through applied external field across the spin
reorientation transition. Our study illustrates novel control of
magneto-dielectricity by tuning the spin reorientation transition in a material
that possess strong spin lattice coupling.Comment: 7 pages, 12 figure
Bulk viscosity in hyperonic star and r-mode instability
We consider a rotating neutron star with the presence of hyperons in its
core, using an equation of state in an effective chiral model within the
relativistic mean field approximation. We calculate the hyperonic bulk
viscosity coefficient due to nonleptonic weak interactions. By estimating the
damping timescales of the dissipative processes, we investigate its role in the
suppression of gravitationally driven instabilities in the -mode. We observe
that -mode instability remains very much significant for hyperon core
temperature of around K, resulting in a comparatively larger instability
window. We find that such instability can reduce the angular velocity of the
rapidly rotating star considerably upto , with as
the Keplerian angular velocity.Comment: 10 pages including 7 figure
Superfluid Phase Stability of He in Axially Anisotropic Aerogel
Measurements of superfluid He in 98% aerogel demonstrate the existence of
a metastable \emph{A}-like phase and a stable \emph{B}-like phase. It has been
suggested that the relative stability of these two phases is controlled by
anisotropic quasiparticle scattering in the aerogel. Anisotropic scattering
produced by axial compression of the aerogel has been predicted to stabilize
the axial state of superfluid He. To explore this possiblity, we used
transverse acoustic impedance to map out the phase diagram of superfluid He
in a % porous silica aerogel subjected to 17% axial compression. We
have previously shown that axial anisotropy in aerogel leads to optical
birefringence and that optical cross-polarization studies can be used to
characterize such anisotropy. Consequently, we have performed optical
cross-polarization experiments to verify the presence and uniformity of the
axial anisotropy in our aerogel sample. We find that uniform axial anisotropy
introduced by 17% compression does not stabilize the \emph{A}-like phase. We
also find an increase in the supercooling of the \emph{A}-like phase at lower
pressure, indicating a modification to \emph{B}-like phase nucleation in
\emph{globally} anisotropic aerogels.Comment: 4 pages, 4 figures, submitted to LT25 (25th International Conference
on Low Temperature Physics
Experimental Evidence of Time Delay Induced Death in Coupled Limit Cycle Oscillators
Experimental observations of time delay induced amplitude death in a pair of
coupled nonlinear electronic circuits that are individually capable of
exhibiting limit cycle oscillations are described. In particular, the existence
of multiply connected death islands in the parameter space of the coupling
strength and the time delay parameter for coupled identical oscillators is
established. The existence of such regions was predicted earlier on theoretical
grounds in [Phys. Rev. Lett. 80, 5109 (1998); Physica 129D, 15 (1999)]. The
experiments also reveal the occurrence of multiple frequency states, frequency
suppression of oscillations with increased time delay and the onset of both
in-phase and anti-phase collective oscillations.Comment: 4 aps formatted RevTeX pages; 6 figures; to appear in Phys. Rev. Let
- …