37,237 research outputs found
Optimization of synchronization in gradient clustered networks
We consider complex clustered networks with a gradient structure, where sizes
of the clusters are distributed unevenly. Such networks describe more closely
actual networks in biophysical systems and in technological applications than
previous models. Theoretical analysis predicts that the network
synchronizability can be optimized by the strength of the gradient field but
only when the gradient field points from large to small clusters. A remarkable
finding is that, if the gradient field is sufficiently strong,
synchronizability of the network is mainly determined by the properties of the
subnetworks in the two largest clusters. These results are verified by
numerical eigenvalue analysis and by direct simulation of synchronization
dynamics on coupled-oscillator networks.Comment: PRE, 76, 056113 (2007
Cusp-scaling behavior in fractal dimension of chaotic scattering
A topological bifurcation in chaotic scattering is characterized by a sudden
change in the topology of the infinite set of unstable periodic orbits embedded
in the underlying chaotic invariant set. We uncover a scaling law for the
fractal dimension of the chaotic set for such a bifurcation. Our analysis and
numerical computations in both two- and three-degrees-of-freedom systems
suggest a striking feature associated with these subtle bifurcations: the
dimension typically exhibits a sharp, cusplike local minimum at the
bifurcation.Comment: 4 pages, 4 figures, Revte
Two-dimensional viscous flow computations of hypersonic scramjet nozzle flowfields at design and off-design conditions
The PARC2D code has been selected to analyze the flowfields of a representative hypersonic scramjet nozzle over a range of flight conditions from Mach 3 to 20. The flowfields, wall pressures, wall skin friction values, heat transfer values and overall nozzle performance are presented
Sheath ionization model of beam emissions from large spacecraft
An analytical model of the charging of a spacecraft emitting electron and ion beams has been applied to the case of large spacecraft. In this model, ionization occurs in the sheath due to the return current. Charge neutralization of spherical space charge flow is examined by solving analytical equations numerically. Parametric studies of potential large spacecraft are performed. As in the case of small spacecraft, the ions created in the sheath by the returning current play a large role in determining spacecraft potential
Trapped photoelectrons during spacecraft charging in sunlight
For a dielectric spacecraft charging in sunlight, the potentials are different on the sunlit and dark sides. Differential charging of spacecraft surfaces can trap low-energy electrons by means of potential wells and barriers. The low-energy electrons are mostly photoelectrons and secondary electrons. Motivated by the recent interest in trapped photoelectrons measured by the Van Allen Probes in the radiation belts, we calculate the extent of the trapped photoelectron area and the potential barrier as a function of the dipole strength and sun angle using the monopole- dipole model. We find that the dipole strength is an important parameter in controlling the behavior of the potential wells and barriers. The usual inequality, 1/2 ≤ A ≤ 1 where A is the dipole strength, used in the monopole-dipole model can be relaxed and amended for finite sun angles. We then use a simple method to estimate the density of the trapped low-energy electrons in these areas. In sunlight charging, the low-energy electron population around the spacecraft is enhanced by the photoelectrons trapped inside the potential barrier
Regional Capital Mobility in China: 1978-2006
We examine cross-region capital mobility in China and track how the degree of mobility has changed over time. The effects of fiscal and redistributive activities of different levels of government in China on private capital mobility are taken into account. Our results indicate that there was a significant improvement in capital mobility over time in China, particularly for private capital in the more developed regions. The central and provincial governments, via their taxation, spending, and transfers, loosen the relationship between private saving and investment and appear to promote capital mobility, particularly for less developed regions. There are considerable differences between more and less developed regions in terms of the degree of capital market integration and the improvement in capital mobility over time. The results have important policy implications on global re-balancing as well as regional development gap and risk-sharing within China.Feldstein-Horioka; Chinese cross-region capital mobility; saving-investment relationship; Chinese capital market integration
Internal localized eigenmodes on spin discrete breathers in antiferromagnetic chains with on-site easy axis anisotropy
We investigate internal localized eigenmodes of the linearized equation
around spin discrete breathers in 1D antiferromagnets with on-site easy axis
anisotropy. The threshold of occurrence of the internal localized eigenmodes
has a typical structure in parameter space depending on the frequency of the
spin discrete breather. We also performed molecular dynamics simulation in
order to show the validity of our linear analysis.Comment: 4 pages including 5 figure
General-relativistic coupling between orbital motion and internal degrees of freedom for inspiraling binary neutron stars
We analyze the coupling between the internal degrees of freedom of neutron
stars in a close binary, and the stars' orbital motion. Our analysis is based
on the method of matched asymptotic expansions and is valid to all orders in
the strength of internal gravity in each star, but is perturbative in the
``tidal expansion parameter'' (stellar radius)/(orbital separation). At first
order in the tidal expansion parameter, we show that the internal structure of
each star is unaffected by its companion, in agreement with post-1-Newtonian
results of Wiseman (gr-qc/9704018). We also show that relativistic interactions
that scale as higher powers of the tidal expansion parameter produce
qualitatively similar effects to their Newtonian counterparts: there are
corrections to the Newtonian tidal distortion of each star, both of which occur
at third order in the tidal expansion parameter, and there are corrections to
the Newtonian decrease in central density of each star (Newtonian ``tidal
stabilization''), both of which are sixth order in the tidal expansion
parameter. There are additional interactions with no Newtonian analogs, but
these do not change the central density of each star up to sixth order in the
tidal expansion parameter. These results, in combination with previous analyses
of Newtonian tidal interactions, indicate that (i) there are no large
general-relativistic crushing forces that could cause the stars to collapse to
black holes prior to the dynamical orbital instability, and (ii) the
conventional wisdom with respect to coalescing binary neutron stars as sources
of gravitational-wave bursts is correct: namely, the finite-stellar-size
corrections to the gravitational waveform will be unimportant for the purpose
of detecting the coalescences.Comment: 22 pages, 2 figures. Replaced 13 July: proof corrected, result
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