43,318 research outputs found
The impact of a wave farm on large scale sediment transport
This study investigates the interactions of waves and tides at a wave farm in the southwest of England, in particular their effects on radiation stress, bottom stress, and consequently on the sediment transport and the coast adjacent to the wave-farm (the Wave Hub). In this study, an integrated complex numerical modelling system is setup at the Wave Hub site and is used to compute the wave and current fields by taking into account the wave-current interaction, as well as the sediment transport. Results show that tidal elevation and tidal currents have a significant effect on the wave height and direction predictions; tidal forcing and wind waves have a significant effect on the bed shear-stress, relevant to sediment transport; waves via radiation stresses have an important effect on the longshore and cross-shore velocity components, particularly during the spring tides. Waves can impact on bottom boundary layer and mixing in the water column. The results highlight the importance of the interactions between waves and tides when modelling coastal morphology with presence of wave energy devices
The induced representations of Brauer algebra and the Clebsch-Gordan coefficients of SO(n)
Induced representations of Brauer algebra from with are discussed. The induction coefficients
(IDCs) or the outer-product reduction coefficients (ORCs) of with up to a normalization factor are
derived by using the linear equation method. Weyl tableaus for the
corresponding Gel'fand basis of SO(n) are defined. The assimilation method for
obtaining CG coefficients of SO(n) in the Gel'fand basis for no modification
rule involved couplings from IDCs of Brauer algebra are proposed. Some
isoscalar factors of for the resulting irrep
with
$\sum\limits_{i=1}^{4}\lambda_{i}\leq .Comment: 48 pages latex, submitted to Journal of Phys.
Suppression of low-energy Andreev states by a supercurrent in YBa_2Cu_3O_7-delta
We report a coherence-length scale phenomenon related to how the high-Tc
order parameter (OP) evolves under a directly-applied supercurrent. Scanning
tunneling spectroscopy was performed on current-carrying YBa_2Cu_3O_7-delta
thin-film strips at 4.2K. At current levels well below the theoretical
depairing limit, the low-energy Andreev states are suppressed by the
supercurrent, while the gap-like structures remain unchanged. We rule out the
likelihood of various extrinsic effects, and propose instead a model based on
phase fluctuations in the d-wave BTK formalism to explain the suppression. Our
results suggest that a supercurrent could weaken the local phase coherence
while preserving the pairing amplitude. Other possible scenarios which may
cause the observed phenomenon are also discussed.Comment: 6 pages, 4 figures, to appear in Physical Review
Transfer Learning for Content-Based Recommender Systems using Tree Matching
In this paper we present a new approach to content-based transfer learning
for solving the data sparsity problem in cases when the users' preferences in
the target domain are either scarce or unavailable, but the necessary
information on the preferences exists in another domain. We show that training
a system to use such information across domains can produce better performance.
Specifically, we represent users' behavior patterns based on topological graph
structures. Each behavior pattern represents the behavior of a set of users,
when the users' behavior is defined as the items they rated and the items'
rating values. In the next step we find a correlation between behavior patterns
in the source domain and behavior patterns in the target domain. This mapping
is considered a bridge between the two domains. Based on the correlation and
content-attributes of the items, we train a machine learning model to predict
users' ratings in the target domain. When we compare our approach to the
popularity approach and KNN-cross-domain on a real world dataset, the results
show that on an average of 83 of the cases our approach outperforms both
methods
A progressive diagonalization scheme for the Rabi Hamiltonian
A diagonalization scheme for the Rabi Hamiltonian, which describes a qubit
interacting with a single-mode radiation field via a dipole interaction, is
proposed. It is shown that the Rabi Hamiltonian can be solved almost exactly
using a progressive scheme that involves a finite set of one variable
polynomial equations. The scheme is especially efficient for lower part of the
spectrum. Some low-lying energy levels of the model with several sets of
parameters are calculated and compared to those provided by the recently
proposed generalized rotating-wave approximation and full matrix
diagonalization.Comment: 8pages, 1 figure, LaTeX. Accepted for publication in J. Phys. B: At.
Mol. Opt. Phy
Extinction of impurity resonances in large-gap regions of inhomogeneous d-wave superconductors
Impurity resonances observed by scanning tunneling spectroscopy in the
superconducting state have been used to deduce properties of the underlying
pure state. Here we study a longstanding puzzle associated with these
measurements, the apparent extinction of these resonances for Ni and Zn
impurities in large-gap regions of the inhomogeneous BSCCO superconductor. We
calculate the effect of order parameter and hopping suppression near the
impurity site, and find that these two effects are sufficient to explain the
missing resonances in the case of Ni. There are several possible scenarios for
the extinction of the Zn resonances, which we discuss in turn; in addition, we
propose measurements which could distinguish among them.Comment: 10 pages, 8 figure
Electromechanical coupling in free-standing AlGaN/GaN planar structures
The strain and electric fields present in free-standing AlGaN/GaN slabs are
examined theoretically within the framework of fully-coupled continuum elastic
and dielectric models. Simultaneous solutions for the electric field and strain
components are obtained by minimizing the electric enthalpy. We apply
constraints appropriate to pseudomorphic semiconductor epitaxial layers and
obtain closed-form analytic expressions that take into account the wurtzite
crystal anisotropy. It is shown that in the absence of free charges, the
calculated strain and electric fields are substantially differently from those
obtained using the standard model without electromechanical coupling. It is
also shown, however, that when a two-dimensional electron gas is present at the
AlGaN/GaN interface, a condition that is the basis for heterojunction
field-effect transistors, the electromechanical coupling is screened and the
decoupled model is once again a good approximation. Specific cases of these
calculations corresponding to transistor and superlattice structures are
discussed.Comment: revte
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