25,843 research outputs found
On the origin of the Fermi arc phenomena in the underdoped cuprates: signature of KT-type superconducting transition
We study the effect of thermal phase fluctuation on the electron spectral
function in a d-wave superconductor with Monte Carlo simulation.
The phase degree of freedom is modeled by a XY-type model with build-in d-wave
character. We find a ridge-like structure emerges abruptly on the underlying
Fermi surface in above the KT-transition temperature of the XY
model. Such a ridge-like structure, which shares the same characters with the
Fermi arc observed in the pseudogap phase of the underdoped cuprates, is found
to be caused by the vortex-like phase fluctuation of the XY model.Comment: 5 page
Data-driven pedestrian re-identification based on hierarchical semantic representation
Limited number of labeled data of surveillance video causes the training of supervised model for pedestrian re-identification to be a difficult task. Besides, applications of pedestrian re-identification in pedestrian retrieving and criminal tracking are limited because of the lack of semantic representation. In this paper, a data-driven pedestrian re-identification model based on hierarchical semantic representation is proposed, extracting essential features with unsupervised deep learning model and enhancing the semantic representation of features with hierarchical mid-level ‘attributes’.
Firstly, CNNs, well-trained with the training process of CAEs, is used to extract features of horizontal blocks segmented from unlabeled pedestrian images. Then, these features are input into corresponding attribute classifiers to judge whether the pedestrian has the attributes. Lastly, with a table of ‘attributes-classes mapping relations’, final result can be calculated. Under the premise of improving the accuracy of attribute classifier, our qualitative results show its clear advantages over the CHUK02, VIPeR, and i-LIDS data set. Our proposed method is proved to effectively solve the problem of dependency on labeled data and lack of semantic expression, and it also significantly outperforms the state-of-the-art in terms of accuracy and semanteme
Coupled cavity QED for coherent control of photon transmission (I): Green function approach for hybrid systems with two-level doping
This is the first one of a series of our papers theoretically studying the
coherent control of photon transmission along the coupled resonator optical
waveguide (CROW) by doping artificial atoms for various hybrid structures. We
will provide the several approaches correspondingly based on Green function,
the mean field method and spin wave theory et al. In the present paper we adopt
the two-time Green function approach to study the coherent transmission photon
in a CROW with homogeneous couplings, each cavity of which is doped by a
two-level artificial atom. We calculate the two-time correlation function for
photon in the weak-coupling case. Its poles predict the exact dispersion
relation, which results in the group velocity coherently controlled by the
collective excitation of the doping atoms. We emphasize the role of the
population inversion of doping atoms induced by some polarization mechanism.Comment: 11 pages, 9 figure
Probing the electron-phonon coupling in ozone-doped graphene by Raman spectroscopy
We have investigated the effects of ozone treatment on graphene by Raman
scattering. Sequential ozone short-exposure cycles resulted in increasing the
doping levels as inferred from the blue shift of the 2 and peak
frequencies, without introducing significant disorder. The two-phonon 2 and
2 Raman peak intensities show a significant decrease, while, on the
contrary, the one-phonon G Raman peak intensity remains constant for the whole
exposure process. The former reflects the dynamics of the photoexcited
electrons (holes) and, specifically, the increase of the electron-electron
scattering rate with doping. From the ratio of 2 to 2 intensities, which
remains constant with doping, we could extract the ratio of electron-phonon
coupling parameters. This ratio is found independent on the number of layers up
to ten layers. Moreover, the rate of decrease of 2 and 2 intensities
with doping was found to slowdown inversely proportional to the number of
graphene layers, revealing the increase of the electron-electron collision
probability
Field-induced structure transformation in electrorheological solids
We have computed the local electric field in a body-centered tetragonal (BCT)
lattice of point dipoles via the Ewald-Kornfeld formulation, in an attempt to
examine the effects of a structure transformation on the local field strength.
For the ground state of an electrorheological solid of hard spheres, we
identified a novel structure transformation from the BCT to the face-centered
cubic (FCC) lattices by changing the uniaxial lattice constant c under the hard
sphere constraint. In contrast to the previous results, the local field
exhibits a non-monotonic transition from BCT to FCC. As c increases from the
BCT ground state, the local field initially decreases rapidly towards the
isotropic value at the body-centered cubic lattice, decreases further, reaching
a minimum value and increases, passing through the isotropic value again at an
intermediate lattice, reaches a maximum value and finally decreases to the FCC
value. An experimental realization of the structure transformation is
suggested. Moreover, the change in the local field can lead to a generalized
Clausius-Mossotti equation for the BCT lattices.Comment: Submitted to Phys. Rev.
Kinetics of viral self-assembly: the role of ss RNA antenna
A big class of viruses self-assemble from a large number of identical capsid
proteins with long flexible N-terminal tails and ss RNA. We study the role of
the strong Coulomb interaction of positive N-terminal tails with ss RNA in the
kinetics of the in vitro virus self-assembly. Capsid proteins stick to
unassembled chain of ss RNA (which we call "antenna") and slide on it towards
the assembly site. We show that at excess of capsid proteins such
one-dimensional diffusion accelerates self-assembly more than ten times. On the
other hand at excess of ss RNA, antenna slows self-assembly down. Several
experiments are proposed to verify the role of ss RNA antenna.Comment: 4 pages, 3 figures, several experiments are proposed, a new idea of
experiment is adde
To travel or not to travel: ‘Weather’ is the question. Modelling the effect of local weather conditions on bus ridership
© 2017 The Authors While the influence of weather on public transport performance and ridership has been the topic for some research, the real-time response of transit usage to variations in weather conditions is yet to be fully understood. This paper redresses this gap by modelling the effect that local weather conditions exert on hourly bus ridership in sub-tropical Brisbane, Australia. Drawing on a transit smart card data set and detailed weather measurements, a suite of time-series regression models are computed to capture the concurrent and lagged effects that weather conditions exert on bus ridership. Our findings highlight that changes in particularly temperature and rainfall were found to induce significant hour-to-hour changes in bus ridership, with such effects varying markedly across both a 24 h period and the transit network. These results are important for public transport service operations in their capacity to inform timely responses to real-time changes in passengers’ travel demand induced by the onset of particular weather conditions
Small ball probability, Inverse theorems, and applications
Let be a real random variable with mean zero and variance one and
be a multi-set in . The random sum
where are iid copies of
is of fundamental importance in probability and its applications.
We discuss the small ball problem, the aim of which is to estimate the
maximum probability that belongs to a ball with given small radius,
following the discovery made by Littlewood-Offord and Erdos almost 70 years
ago. We will mainly focus on recent developments that characterize the
structure of those sets where the small ball probability is relatively
large. Applications of these results include full solutions or significant
progresses of many open problems in different areas.Comment: 47 page
Physicochemical factors impacting CO2 sequestration in depleted shale formations: The case of the Utica shale
AbstractFractured shale formations could serve as an attractive target formation for geologic carbon sequestration once they have been depleted of hydrocarbons. The low intrinsic permeability of the shale matrix could reduce the CO2 leakage potential, the kerogen in the shale would provide a matrix within which the CO2 can be permanently sorbed, and the infrastructure in place at gas production sites could all be leveraged to minimize costs. Here, a modeling framework previously developed by the authors to estimate the sequestration capacity of shale formations is extended to better capture the physicochemical realities associated with injecting CO2 into fractured shale formations. The model uses CH4 production data to fit key parameters about the formation and applies those to a unipore diffusion model to characterize the controlling gas transport processes. A number of parameters, including the gas diffusion coefficient, the ratio of adsorbed gas to free phase gas, water saturation and gas adsorption isotherms are considered and their effect on modeling estimates is explored. The model is found to be most sensitive to the ratio of adsorbed gas to the total gas which includes both adsorbed and free phase gas. The equilibrium adsorption parameters of CH4 and CO2 also have significant influence largely because published estimates for these parameters vary considerably. The effect of pore collapse following production was explored in terms of its effect on characteristic diffusion length. The results indicate that increasing this characteristics length by an order of five would triple the time it takes to complete the injection of CO2 into the formation. Similarly, an increase in water content in the formation or in the ratio of free CH4 to sorbed CH4 would decrease the sequestration potential of the formation. Based on this improved constitutive understanding of the modeling inputs and the estimates, the CO2 sequestration capacity of the Utica Shale was calculated and the results were compared with those from Marcellus Shale. The differences could be understood in terms of the distinct petrophysical properties of those two shale formations. This analysis provides recommendations about experimental directions that could be very useful for improving the accuracy of sequestration capacity models
Linear Continuum Mechanics for Quantum Many-Body Systems
We develop the continuum mechanics of quantum many-body systems in the linear
response regime. The basic variable of the theory is the displacement field,
for which we derive a closed equation of motion under the assumption that the
time-dependent wave function in a locally co-moving reference frame can be
described as a geometric deformation of the ground-state wave function. We show
that this equation of motion is exact for systems consisting of a single
particle, and for all systems at sufficiently high frequency, and that it leads
to an excitation spectrum that has the correct integrated strength. The theory
is illustrated by simple model applications to one- and two-electron systems.Comment: 4 pages, 1 figure, 1 tabl
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