9,599 research outputs found
Aging in the Relaxor Ferroelectric PMN/PT
The relaxor ferroelectric
(PbMnNbO)(PbTiO), ,
(PMN/PT(90/10)) is found to exhibit several regimes of complicated aging
behavior. Just below the susceptibility peak there is a regime exhibiting
rejuvenation but little memory. At lower temperature, there is a regime with
mainly cumulative aging, expected for simple domain-growth. At still lower
temperature, there is a regime with both rejuvenation and memory, reminiscent
of spin glasses. PMN/PT (88/12) is also found to exhibit some of these aging
regimes. This qualitative aging behavior is reminiscent of that seen in
reentrant ferromagnets, which exhibit a crossover from a domain-growth
ferromagnetic regime into a reentrant spin glass regime at lower temperatures.
These striking parallels suggest a picture of competition in PMN/PT (90/10)
between ferroelectric correlations formed in the domain-growth regime with
glassy correlations formed in the spin glass regime. PMN/PT (90/10) is also
found to exhibit frequency-aging time scaling of the time-dependent part of the
out-of-phase susceptibility for temperatures 260 K and below. The stability of
aging effects to thermal cycles and field perturbations is also reported.Comment: 8 pages RevTeX4, 11 figures; submitted to Phys. Rev.
Dividing the Ontology Alignment Task with Semantic Embeddings and Logic-based Modules
Large ontologies still pose serious challenges to state-of-the-art ontology alignment systems. In this paper we present an approach that combines a neural embedding model and logic-based modules to accurately divide an input ontology matching task into smaller and more tractable matching (sub)tasks. We have conducted a comprehensive evaluation using the datasets of the Ontology Alignment Evaluation Initiative. The results are encouraging and suggest that the proposed method is adequate in practice and can be integrated within the workflow of systems unable to cope with very large ontologies
Studies of surface two-dimensional photonic band-gap structures
Two-dimensional (2D) surface photonic band-gap (SPBG) structures can be obtained by providing a shallow corrugation of the inner surface of a waveguide wall. It can be used as a distributed mirror, a cavity, or a filter in integrated optics or microwave electronics. These structures can also be an alternative to conventional 2D PBG or 1D Bragg structures. In this article, we present the results of theoretical and experimental studies of 2D SPBG structures. Data obtained from experiments are compared with theoretical results and good agreement between theory and experiment is demonstrated. Comparison of a coaxial 2D SPBG structure with a conventional 1D Bragg structure is also presented
Two-step phase changes in cubic relaxor ferroelectrics
The field-driven conversion between the zero-field-cooled frozen relaxor
state and a ferroelectric state of several cubic relaxors is found to occur in
at least two distinct steps, after a period of creep, as a function of time.
The relaxation of this state back to a relaxor state under warming in zero
field also occurs via two or more sharp steps, in contrast to a one-step
relaxation of the ferroelectric state formed by field-cooling. An intermediate
state can be trapped by interrupting the polarization. Giant pyroelectric noise
appears in some of the non-equilibrium regimes. It is suggested that two
coupled types of order, one ferroelectric and the other glassy, may be required
to account for these data.Comment: 27 pages with 8 figures to appear in Phys. Rev.
Spread of Infectious Diseases with a Latent Period
Infectious diseases spread through human networks.
Susceptible-Infected-Removed (SIR) model is one of the epidemic models to
describe infection dynamics on a complex network connecting individuals. In the
metapopulation SIR model, each node represents a population (group) which has
many individuals. In this paper, we propose a modified metapopulation SIR model
in which a latent period is taken into account. We call it SIIR model. We
divide the infection period into two stages: an infected stage, which is the
same as the previous model, and a seriously ill stage, in which individuals are
infected and cannot move to the other populations. The two infectious stages in
our modified metapopulation SIR model produce a discontinuous final size
distribution. Individuals in the infected stage spread the disease like
individuals in the seriously ill stage and never recover directly, which makes
an effective recovery rate smaller than the given recovery rate.Comment: 6 pages, 3 figure
Cylindrical, periodic surface lattice — theory, dispersion analysis, and experiment
A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model
Mean flow and spiral defect chaos in Rayleigh-Benard convection
We describe a numerical procedure to construct a modified velocity field that
does not have any mean flow. Using this procedure, we present two results.
Firstly, we show that, in the absence of mean flow, spiral defect chaos
collapses to a stationary pattern comprising textures of stripes with angular
bends. The quenched patterns are characterized by mean wavenumbers that
approach those uniquely selected by focus-type singularities, which, in the
absence of mean flow, lie at the zig-zag instability boundary. The quenched
patterns also have larger correlation lengths and are comprised of rolls with
less curvature. Secondly, we describe how mean flow can contribute to the
commonly observed phenomenon of rolls terminating perpendicularly into lateral
walls. We show that, in the absence of mean flow, rolls begin to terminate into
lateral walls at an oblique angle. This obliqueness increases with Rayleigh
number.Comment: 14 pages, 19 figure
PACE into fruit tree spraying practice
A concerted effort was made over a 2 year period (2012-13) to transfer the webpage linked PACE (Pesticide dose Adjustment to the Crop Environment) (Walklate and Cross 2013a) system into commercial practice in the UK and to test the results of its implementation on 7 commercial tree fruit farms, feeding back the results to growers and industry. The aim of PACE is to support lo
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