2,855 research outputs found
Magnetic ordering of nitrogen-vacancy centers in diamond via resonator-mediated coupling
Nitrogen-vacancy centers in diamond, being a promising candidate for quantum
information processing, may also be an ideal platform for simulating many-body
physics. However, it is difficult to realize interactions between
nitrogen-vacancy centers strong enough to form a macroscopically ordered phase
under realistic temperatures. Here we propose a scheme to realize long-range
ferromagnetic Ising interactions between distant nitrogen-vacancy centers by
using a mechanical resonator as a medium. Since the critical temperature in the
long-range Ising model is proportional to the number of spins, a ferromagnetic
order can be formed at a temperature of tens of millikelvin for a sample with
nitrogen-vacancy centers. This method may provide a new platform for
studying many-body physics using qubit systems.Comment: 5 pages, 4 figure
Towards Understanding Astrophysical Effects of Nuclear Symmetry Energy
Determining the Equation of State (EOS) of dense neutron-rich nuclear matter
is a shared goal of both nuclear physics and astrophysics. Except possible
phase transitions, the density dependence of nuclear symmetry \esym is the most
uncertain part of the EOS of neutron-rich nucleonic matter especially at
supra-saturation densities. Much progresses have been made in recent years in
predicting the symmetry energy and understanding why it is still very uncertain
using various microscopic nuclear many-body theories and phenomenological
models. Simultaneously, significant progresses have also been made in probing
the symmetry energy in both terrestrial nuclear laboratories and astrophysical
observatories. In light of the GW170817 event as well as ongoing or planned
nuclear experiments and astrophysical observations probing the EOS of dense
neutron-rich matter, we review recent progresses and identify new challenges to
the best knowledge we have on several selected topics critical for
understanding astrophysical effects of the nuclear symmetry energy.Comment: 77 pages. Invited Review Article, EPJA (2019) in pres
Joint Extraction of Entities and Relations Based on a Novel Tagging Scheme
Joint extraction of entities and relations is an important task in
information extraction. To tackle this problem, we firstly propose a novel
tagging scheme that can convert the joint extraction task to a tagging problem.
Then, based on our tagging scheme, we study different end-to-end models to
extract entities and their relations directly, without identifying entities and
relations separately. We conduct experiments on a public dataset produced by
distant supervision method and the experimental results show that the tagging
based methods are better than most of the existing pipelined and joint learning
methods. What's more, the end-to-end model proposed in this paper, achieves the
best results on the public dataset
Aspect ratio dependence of heat transport by turbulent Rayleigh-B\'{e}nard convection in rectangular cells
We report high-precision measurements of the Nusselt number as a
function of the Rayleigh number in water-filled rectangular
Rayleigh-B\'{e}nard convection cells. The horizontal length and width
of the cells are 50.0 cm and 15.0 cm, respectively, and the heights ,
25.0, 12.5, 6.9, 3.5, and 2.4 cm, corresponding to the aspect ratios
, , ,
, , and . The measurements were carried out
over the Rayleigh number range and the
Prandtl number range . Our results show that for
rectangular geometry turbulent heat transport is independent of the cells'
aspect ratios and hence is insensitive to the nature and structures of the
large-scale mean flows of the system. This is slightly different from the
observations in cylindrical cells where is found to be in general a
decreasing function of , at least for and larger. Such a
difference is probably a manifestation of the finite plate conductivity effect.
Corrections for the influence of the finite conductivity of the top and bottom
plates are made to obtain the estimates of for plates with
perfect conductivity. The local scaling exponents of are calculated and found to increase from 0.243 at
to 0.327 at .Comment: 15 pages, 7 figures, Accepted by Journal of Fluid Mechanic
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