1,739 research outputs found
Novel Two-dimensional Carbon Allotrope with Strong Electronic Anisotropy
Two novel two-dimensional carbon allotropes comprised of octagons and
pentagons are proposed based on the first-principles calculations. The two
carbon allotropes, named OPG-L and OPG-Z, are found to have distinct
properties. OPG-L is metallic, while OPG-Z is a gapless semimetal. Remarkably,
OPG-Z exhibits pronounced electronic anisotropy with highly anisotropic Dirac
points at the Fermi level. A tight-binding model is suggested to describe the
low-energy quasiparticles, which clarifies the origin of the anisotropic Dirac
points. Such an anisotropic electronic characteristic of OPG-Z is expected to
have wide implications in nano-electronics.Comment: 6 pages, 5 figures (accepted by Physical Review B
Efficient Spatial Keyword Search in Trajectory Databases
An increasing amount of trajectory data is being annotated with text
descriptions to better capture the semantics associated with locations. The
fusion of spatial locations and text descriptions in trajectories engenders a
new type of top- queries that take into account both aspects. Each
trajectory in consideration consists of a sequence of geo-spatial locations
associated with text descriptions. Given a user location and a
keyword set , a top- query returns trajectories whose text
descriptions cover the keywords and that have the shortest match
distance. To the best of our knowledge, previous research on querying
trajectory databases has focused on trajectory data without any text
description, and no existing work has studied such kind of top- queries on
trajectories. This paper proposes one novel method for efficiently computing
top- trajectories. The method is developed based on a new hybrid index,
cell-keyword conscious B-tree, denoted by \cellbtree, which enables us to
exploit both text relevance and location proximity to facilitate efficient and
effective query processing. The results of our extensive empirical studies with
an implementation of the proposed algorithms on BerkeleyDB demonstrate that our
proposed methods are capable of achieving excellent performance and good
scalability.Comment: 12 page
Clinical observation of torsional phacoemulsification for a beginner
AIM: To observe the clinical security of torsional phacoemulsification for a beginner.<p>METHODS: The clinical data of 200 eyes who accepted torsional phacoemulsification by a beginner from February 2012 to March 2013 were reviewed. The operation complications were analyzed and the postoperative effect was assessed.<p>RESULTS: There was no collapse of the anterior chamber during operation. When the last nuclear was removed the surge occurred mildly. Posterior capsular rupture happened in 8 eyes, 5 eyes' intraocular lens#IOL#implanted in sclera sulcus after anterior vitrectomy, 3 eyes' IOL in bag without vitreous outflow. One eye without continuous curvilinear capsulotomy was transferred to the superior doctor for extracapsular cataract extraction#ECCE#. One eye with the loose zonular fiber was implanted a capsular tension ring by the superior doctor. Seven cases need suture because of short sclera tunnel incisions. Uncorrected visual acuity a week after operation: 2 eyes#1%#<0.05, 31 eyes#15.5%#0.05-<0.3, 64 eyes#32%#≥0.3, 103 eyes#51.5%#≥0.5. There was no grade 3 corneal edema. The high intraocular pressure can be controlled by anterior chamber penetration or drugs.<p>CONCLUSION: The technique of torsional phacoemulsification is safe and effective for a beginner
Transport properties of dense deuterium-tritium plasmas
Consistent descriptions of the equation of states, and information about
transport coefficients of deuterium-tritium mixture are demonstrated through
quantum molecular dynamic (QMD) simulations (up to a density of 600 g/cm
and a temperature of eV). Diffusion coefficients and viscosity are
compared with one component plasma model in different regimes from the strong
coupled to the kinetic one. Electronic and radiative transport coefficients,
which are compared with models currently used in hydrodynamic simulations of
inertial confinement fusion, are evaluated up to 800 eV. The Lorentz number is
also discussed from the highly degenerate to the intermediate region.Comment: 4 pages, 3 figure
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