25,871 research outputs found
Opportunities for weed manipulation using GMHT row crops
The herbicides and cultivation systems available in most non-GM crops allow farmers little flexibility as to when they control weeds. However, glyphosate and glufosinate-ammonium, as used in GM herbicide tolerant crops, offer the opportunity to control large weeds and weed control can be timed according to the agronomic and environmental aims of the user. This paper will use sugar beet as a model crop and report results where different approaches to weed control have been used and discuss their relevance in the wider agricultural and environmental contextNon peer reviewe
An edge index for the Quantum Spin-Hall effect
Quantum Spin-Hall systems are topological insulators displaying
dissipationless spin currents flowing at the edges of the samples. In
contradistinction to the Quantum Hall systems where the charge conductance of
the edge modes is quantized, the spin conductance is not and it remained an
open problem to find the observable whose edge current is quantized. In this
paper, we define a particular observable and the edge current corresponding to
this observable. We show that this current is quantized and that the
quantization is given by the index of a certain Fredholm operator. This
provides a new topological invariant that is shown to take same values as the
Spin-Chern number previously introduced in the literature. The result gives an
effective tool for the investigation of the edge channels' structure in Quantum
Spin-Hall systems. Based on a reasonable assumption, we also show that the edge
conducting channels are not destroyed by a random edge.Comment: 4 pages, 3 figure
Real-time motion data annotation via action string
Even though there is an explosive growth of motion capture data, there is still a lack of efficient and reliable methods to automatically annotate all the motions in a database. Moreover, because of the popularity of mocap devices in home entertainment systems, real-time human motion annotation or recognition becomes more and more imperative. This paper presents a new motion annotation method that achieves both the aforementioned two targets at the same time. It uses a probabilistic pose feature based on the Gaussian Mixture Model to represent each pose. After training a clustered pose feature model, a motion clip could be represented as an action string. Then, a dynamic programming-based string matching method is introduced to compare the differences between action strings. Finally, in order to achieve the real-time target, we construct a hierarchical action string structure to quickly label each given action string. The experimental results demonstrate the efficacy and efficiency of our method
Electromagnetically induced transparency in an inverted Y-type four-level system
The interaction of a weak probe laser with an inverted-Y type four-level
atomic system driven by two additional coherent fields is investigated
theoretically. Under the influence of the coherent coupling fields, the
steady-state linear susceptibility of the probe laser shows that the system can
have single or double electromagnetically induced transparency windows
depending on the amplitude and the detuning of the coupling lasers. The
corresponding index of refraction associated with the group velocity of the
probe laser can be controlled at both transparency windows by the coupling
fields. The propagation of the probe field can be switched from superluminal
near the resonance to subluminal on resonance within the single transparency
window when two coupling lasers are on resonance. This provides a potential
application in quantum information processing. We propose an atomic
system for experimental observation
Double-Layer Bose-Einstein Condensates with Large Number of Vortices
In this paper we systematically study the double layer vortex lattice model,
which is proposed to illustrate the interplay between the physics of a fast
rotating Bose-Einstein condensate and the macroscopic quantum tunnelling. The
phase diagram of the system is obtained. We find that under certain conditions
the system will exhibit one novel phase transition, which is consequence of
competition between inter-layer coherent hopping and inter-layer
density-density interaction. In one phase the vortices in one layer coincide
with those in the other layer. And in another phase two sets of vortex lattices
are staggered, and as a result the quantum tunnelling between two layers is
suppressed. To obtain the phase diagram we use two kinds of mean field theories
which are quantum Hall mean field and Thomas-Fermi mean field. Two different
criteria for the transition taking place are obtained respectively, which
reveals some fundamental differences between these two mean field states. The
sliding mode excitation is also discussed.Comment: 12 pages, 8 figure
Cu/Ag EAM Potential Optimized for Heteroepitaxial Diffusion from ab initio Data
A binary embedded-atom method (EAM) potential is optimized for Cu on Ag(111)
by fitting to ab initio data. The fitting database consists of DFT calculations
of Cu monomers and dimers on Ag(111), specifically their relative energies,
adatom heights, and dimer separations. We start from the Mishin Cu-Ag EAM
potential and first modify the Cu-Ag pair potential to match the FCC/HCP site
energy difference then include Cu-Cu pair potential optimization for the entire
database. The optimized EAM potential reproduce DFT monomer and dimer relative
energies and geometries correctly. In trimer calculations, the potential
produces the DFT relative energy between FCC and HCP trimers, though a
different ground state is predicted. We use the optimized potential to
calculate diffusion barriers for Cu monomers, dimers, and trimers. The
predicted monomer barrier is the same as DFT, while experimental barriers for
monomers and dimers are both lower than predicted here. We attribute the
difference with experiment to the overestimation of surface adsorption energies
by DFT and a simple correction is presented. Our results show that the
optimized Cu-Ag EAM can be applied in the study of larger Cu islands on
Ag(111).Comment: 15 pages, 7 figure
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