1,242 research outputs found
Study of axial strain induced torsion of single wall carbon nanotubes by 2D continuum anharmonic anisotropic elastic model
Recent molecular dynamic simulations have found chiral single wall carbon
nanotubes (SWNTs) twist during stretching, which is similar to the motion of a
screw. Obviously this phenomenon, as a type of curvature-chirality effect, can
not be explained by usual isotropic elastic theory of SWNT. More interestingly,
with larger axial strains (before buckling), the axial strain induced torsion
(a-SIT) shows asymmetric behaviors for axial tensile and compressing strains,
which suggests anharmonic elasticity of SWNTs plays an important role in real
a-SIT responses. In order to study the a-SIT of chiral SWNTs with actual sizes,
and avoid possible deviations of computer simulation results due to the
finite-size effect, we propose a 2D analytical continuum model which can be
used to describe the the SWNTs of arbitrary chiralities, curvatures, and
lengths, with the concerning of anisotropic and anharmonic elasticity of SWNTs.
This elastic energy of present model comes from the continuum limit of lattice
energy based on Second Generation Reactive Empirical Bond Order potential
(REBO-II), a well-established empirical potential for solid carbons. Our model
has no adjustable parameters, except for those presented in REBO-II, and all
the coefficients in the model can be calculated analytically. Using our method,
we obtain a-SIT responses of chiral SWNTs with arbitrary radius, chiralities
and lengthes. Our results are in reasonable agreement with recent molecular
dynamic simulations. [Liang {\it et. al}, Phys. Rev. Lett, , 165501
(2006).] Our approach can also be used to calculate other curvature-chirality
dependent anharmonic mechanic responses of SWNTs.Comment: 14 pages, 2 figure
Low-Resource Response Generation with Template Prior
We study open domain response generation with limited message-response pairs.
The problem exists in real-world applications but is less explored by the
existing work. Since the paired data now is no longer enough to train a neural
generation model, we consider leveraging the large scale of unpaired data that
are much easier to obtain, and propose response generation with both paired and
unpaired data. The generation model is defined by an encoder-decoder
architecture with templates as prior, where the templates are estimated from
the unpaired data as a neural hidden semi-markov model. By this means, response
generation learned from the small paired data can be aided by the semantic and
syntactic knowledge in the large unpaired data. To balance the effect of the
prior and the input message to response generation, we propose learning the
whole generation model with an adversarial approach. Empirical studies on
question response generation and sentiment response generation indicate that
when only a few pairs are available, our model can significantly outperform
several state-of-the-art response generation models in terms of both automatic
and human evaluation.Comment: Accepted by EMNLP201
Spontaneous Symmetry Breaking of Vortex Number in Binary Alternating Current Countersuperflow
In binary superfluid counterflow systems, vortex nucleation arises as a
consequence of hydrodynamic instabilities when the coupling coefficient and
counterflow velocity exceed the critical value. When dealing with two identical
components, one might naturally anticipate that the number of vortices
generated would remain equal. However, through the numerical experiments of the
holographic model and the Gross-Pitaevskii equation, our investigation has
unveiled a remarkable phenomenon: in Alternating Current counterflow systems,
once the coupling coefficient and frequency exceed certain critical values, a
surprising symmetry-breaking phenomenon occurs. This results in an asymmetry in
the number of vortices in the two components. We establish that this phenomenon
represents a novel continuous phase transition, which, as indicated by the
phase diagram, is exclusively observable in Alternating Current counterflow. We
provide an explanation for this intriguing phenomenon through soliton
structures, thereby uncovering the complex and unique characteristics of
quantum fluid instabilities and their rich phenomena.Comment: 13 pages,14 figure
Nanocrystals in silicon photonic crystal standing-wave cavities as spin-photon phase gates for quantum information processing
By virtue of a silicon high-Q photonic crystal nanocavity, we propose and
examine theoretically interactions between a stationary electron spin qubit of
a semiconductor nanocrystal and a flying photon qubit. Firstly, we introduce,
derive and demonstrate for the first time the explicit conditions towards
realization of a spin-photon two-qubit phase gate, and propose these
interactions as a generalized quantum interface for quantum information
processing. Secondly, we examine novel single-spin-induced reflections as
direct evidence of intrinsic bare and dressed modes in our coupled
nanocrystal-cavity system. The excellent physical integration of this silicon
system provides tremendous potential for large-scale quantum information
processing
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