391 research outputs found
Composite-fermion crystallites in quantum dots
The correlations in the ground state of interacting electrons in a
two-dimensional quantum dot in a high magnetic field are known to undergo a
qualitative change from liquid-like to crystal-like as the total angular
momentum becomes large. We show that the composite-fermion theory provides an
excellent account of the states in both regimes. The quantum mechanical
formation of composite fermions with a large number of attached vortices
automatically generates omposite fermion crystallites in finite quantum dots.Comment: 5 pages, 3 figure
Autonomous stochastic resonance in fully frustrated Josephson-junction ladders
We investigate autonomous stochastic resonance in fully frustrated
Josephson-junction ladders, which are driven by uniform constant currents. At
zero temperature large currents induce oscillations between the two ground
states, while for small currents the lattice potential forces the system to
remain in one of the two states. At finite temperatures, on the other hand,
oscillations between the two states develop even below the critical current;
the signal-to-noise ratio is found to display array-enhanced stochastic
resonance. It is suggested that such behavior may be observed experimentally
through the measurement of the staggered voltage.Comment: 6 pages, 11 figures, to be published in Phys. Rev.
3D target localization of modified 3D MUSIC for a triple-channel K-band radar
In this paper, a modified 3D multiple signal classification (MUSIC) algorithm is proposed for joint estimation of range, azimuth, and elevation angles of K-band radar with a small 2 × 2 horn antenna array. Three channels of the 2 × 2 horn antenna array are utilized as receiving channels, and the other one is a transmitting antenna. The proposed modified 3D MUSIC is designed to make use of a stacked autocorrelation matrix, whose element matrices are related to each other in the spatial domain. An augmented 2D steering vector based on the stacked autocorrelation matrix is proposed for the modified 3D MUSIC, instead of the conventional 3D steering vector. The effectiveness of the proposed modified 3D MUSIC is verified through implementation with a K-band frequency-modulated continuous-wave (FMCW) radar with the 2 × 2 horn antenna array through a variety of experiments in a chamber. © 2018 by the authors. Licensee MDPI, Basel, Switzerland.1
Social network market: Storytelling on a web 2.0 original literature site
This article looks at a Chinese Web 2.0 original literature site, Qidian, in order to show the coevolution of market and non-market initiatives. The analytic framework of social network markets (Potts et al., 2008) is employed to analyse the motivations of publishing original literature works online and to understand the support mechanisms of the site, which encourage readers’ willingness to pay for user-generated content. The co-existence of socio-cultural and commercial economies and their impact on the successful business model of the site are illustrated in this case. This article extends the concept of social network markets by proposing the existence of a ripple effect of social network markets through convergence between PC and mobile internet, traditional and internet publishing, and between publishing and other cultural industries. It also examines the side effects of social network markets, and the role of market and non-market strategies in addressing the issues
Evidence for partial melt in the crust beneath Mt. Paektu (Changbaishan), Democratic People's Republic of Korea and China
Mt. Paektu (also known as Changbaishan) is an enigmatic volcano on the border between the Democratic People's Republic of Korea (DPRK) and China. Despite being responsible for one of the largest eruptions in history, comparatively little is known about its magmatic evolution, geochronology, or underlying structure. We present receiver function results from an unprecedented seismic deployment in the DPRK. These are the first estimates of the crustal structure on the DPRK side of the volcano and, indeed, for anywhere beneath the DPRK. The crust 60 km from the volcano has a thickness of 35 km and a bulk / of 1.76, similar to that of the Sino-Korean craton. The / ratio increases ~20 km from the volcano, rising to >1.87 directly beneath the volcano. This shows that a large region of the crust has been modified by magmatism associated with the volcanism. Such high values of / suggest that partial melt is present in the crust beneath Mt. Paektu. This region of melt represents a potential source for magmas erupted in the last few thousand years and may be associated with an episode of volcanic unrest observed between 2002 and 2005.This work was supported by the Richard Lounsbery Foundation. The UK seismic instruments and data management facilities were provided under loan number 976 by SEIS-UK at the University of Leicester. The facilities of SEIS-UK are supported by the NERC under Agreement R8/H10/64. J.O.S.H. was supported by an NERC Fellowship NE/I020342/1
Quantum phase transitions in superconducting arrays under external magnetic fields
We study the zero-temperature phase transitions of two-dimensional
superconducting arrays with both the self- and the junction capacitances in the
presence of external magnetic fields. We consider two kinds of excitations from
the Mott insulating phase: charge-dipole excitations and single-charge
excitations, and apply the second-order perturbation theory to find their
energies. The resulting phase boundaries are found to depend strongly on the
magnetic frustration, which measures the commensurate-incommensurate effects.
Comparison of the obtained values with those in recent experiment suggests the
possibility that the superconductor-insulator transition observed in experiment
may not be of the Berezinskii-Kosterlitz-Thouless type. The system is also
transformed to a classical three-dimensional XY model with the magnetic field
in the time-direction; this allows the analogy to bulk superconductors,
revealing the nature of the phase transitions.Comment: 9 pages including 7 figures, to appear in Phys. Rev.
Spatiotemporal Stochastic Resonance in Fully Frustrated Josephson Ladders
We consider a Josephson-junction ladder in an external magnetic field with
half flux quantum per plaquette. When driven by external currents, periodic in
time and staggered in space, such a fully frustrated system is found to display
spatiotemporal stochastic resonance under the influence of thermal noise. Such
resonance behavior is investigated both numerically and analytically, which
reveals significant effects of anisotropy and yields rich physics.Comment: 8 pages in two columns, 8 figures, to appear in Phys. Rev.
XY model in small-world networks
The phase transition in the XY model on one-dimensional small-world networks
is investigated by means of Monte-Carlo simulations. It is found that
long-range order is present at finite temperatures, even for very small values
of the rewiring probability, suggesting a finite-temperature transition for any
nonzero rewiring probability. Nature of the phase transition is discussed in
comparison with the globally-coupled XY model.Comment: 5 pages, accepted in PR
Relaxation and Coarsening Dynamics in Superconducting Arrays
We investigate the nonequilibrium coarsening dynamics in two-dimensional
overdamped superconducting arrays under zero external current, where ohmic
dissipation occurs on junctions between superconducting islands through uniform
resistance. The nonequilibrium relaxation of the unfrustrated array and also of
the fully frustrated array, quenched to low temperature ordered states or
quasi-ordered ones, is dominated by characteristic features of coarsening
processes via decay of point and line defects, respectively. In the case of
unfrustrated arrays, it is argued that due to finiteness of the friction
constant for a vortex (in the limit of large spatial extent of the vortex), the
typical length scale grows as accompanied by the number
of point vortices decaying as . This is in contrast with the
case that dominant dissipation occurs between each island and the substrate,
where the friction constant diverges logarithmically and the length scale
exhibits diffusive growth with a logarithmic correction term. We perform
extensive numerical simulations, to obtain results in reasonable agreement. In
the case of fully frustrated arrays, the domain growth of Ising-like chiral
order exhibits the low-temperature behavior , with the
growth exponent apparently showing a strong temperature dependence in
the low-temperature limit.Comment: 9 pages, 5 figures, to be published in Phys. Rev.
- …