20,893 research outputs found
Classification of Overlapped Audio Events Based on AT, PLSA, and the Combination of Them
Audio event classification, as an important part of Computational Auditory Scene Analysis, has attracted much attention. Currently, the classification technology is mature enough to classify isolated audio events accurately, but for overlapped audio events, it performs much worse. While in real life, most audio documents would have certain percentage of overlaps, and so the overlap classification problem is an important part of audio classification. Nowadays, the work on overlapped audio event classification is still scarce, and most existing overlap classification systems can only recognize one audio event for an overlap. In this paper, in order to deal with overlaps, we innovatively introduce the author-topic (AT) model which was first proposed for text analysis into audio classification, and innovatively combine it with PLSA (Probabilistic Latent Semantic Analysis). We propose 4 systems, i.e. AT, PLSA, AT-PLSA and PLSA-AT, to classify overlaps. The 4 proposed systems have the ability to recognize two or more audio events for an overlap. The experimental results show that the 4 systems perform well in classifying overlapped audio events, whether it is the overlap in training set or the overlap out of training set. Also they perform well in classifying isolated audio events
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Modelling local amenities with online open-source data in a new spatial equilibrium model: Insights from applications for Beijing
This paper presents a new, general purpose method for modelling local
amenities in a city-level spatial equilibrium model with emerging data
sources. A log-form utility function is introduced to differentiate local
amenities from other hard-to-observe influences of locational choice for
residential and job location. In particular, we use the online open data of
schools and hospitals in Beijing to improve model parameterization and
calibration at high spatial resolution. The new local amenities element can improve the model’s fidelity on residence location choice by over 30%,
which is a step forward in decomposing the zonal attractiveness in spatial
equilibrium models. Moreover the local amenities component provides a
new interface for the spatial equilibrium models, where quantification of
the combined effects of urban land-use and local amenities policies can be simulated on a more consistent basis. The calibrated model of Beijing
shows that the coordination of local amenities provision has significant
impacts on the performance of urban spatial strategies. Uncoordinated local amenities provision may undermine or even overturn the long-term
plans for building a polycentric city region
Searching for Dark Matter Signals in the Left-Right Symmetric Gauge Model with CP Symmetry
We investigate singlet scalar dark matter (DM) candidate in a left-right
symmetric gauge model with two Higgs bidoublets (2HBDM) in which the
stabilization of the DM particle is induced by the discrete symmetries P and
CP. According to the observed DM abundance, we predict the DM direct and
indirect detection cross sections for the DM mass range from 10 GeV to 500 GeV.
We show that the DM indirect detection cross section is not sensitive to the
light Higgs mixing and Yukawa couplings except the resonance regions. The
predicted spin-independent DM-nucleon elastic scattering cross section is found
to be significantly dependent on the above two factors. Our results show that
the future DM direct search experiments can cover the most parts of the allowed
parameter space. The PAMELA antiproton data can only exclude two very narrow
regions in the 2HBDM. It is very difficult to detect the DM direct or indirect
signals in the resonance regions due to the Breit-Wigner resonance effect.Comment: 24 pages, 8 figures. minor changes and a reference added, published
in Phys. Rev.
Fluctuation of Conductance Peak Spacings in Large Semiconductor Quantum Dots
Fluctuation of Coulomb blockade peak spacings in large two-dimensional
semiconductor quantum dots are studied within a model based on the
electrostatics of several electron islands among which there are random
inductive and capacitive couplings. Each island can accommodate electrons on
quantum orbitals whose energies depend also on an external magnetic field. In
contrast with a single island quantum dot, where the spacing distribution is
close to Gaussian, here the distribution has a peak at small spacing value. The
fluctuations are mainly due to charging effects. The model can explain the
occasional occurrence of couples or even triples of closely spaced Coulomb
blockade peaks, as well as the qualitative behavior of peak positions with the
applied magnetic field.Comment: 13 pages, 4 figures, accepted for publication in PR
Heat current and spin current through a carbon-nanotube-based molecular quantum pump
We investigate the heat current and spin current through a carbon-nanotube-based molecular quantum pump. We have derived a general expression for the heat current at finite frequency so that the heat current can be calculated order by order in pumping amplitudes. We have applied our theory to a carbon-nanotube-based quantum pump. The heat current generated during the parametric pumping has been calculated at small frequencies for finite pumping amplitude. At finite frequencies, we have calculated the heat current to the second order in pumping amplitudes. The photon assisted process is clearly observed in the heat current. In the presence of magnetic field, the carbon-nanotube-based quantum pump can function as a spin pump, a molecular device by which a dc pure spin current without accompanying charge current is generated at zero bias voltage via a cyclic deformation of two device parameters. The pure spin current is achieved when the Fermi energy is near the resonant level of the quantum pump. We find that the pure spin current is sensitive to system parameters such as pumping amplitude, external magnetic field, and gate voltage.published_or_final_versio
A Particle Element Approach for Modelling the 3D Printing Process of Fibre Reinforced Polymer Composites
This paper presents a new numerical approach for modelling the 3D printing process of fibre reinforced polymer composites by fused deposition modelling (FDM). The approach is based on the coupling between two particle methods, namely smoothed particle hydrodynamics (SPH) and discrete element method (DEM). The coupled SPH-DEM model has distinctive advantages in dealing with the free surface flow, large deformation of fibres, and/or fibre-fibre interaction that are involved in the FDM process. A numerical feasibility study is carried out to demonstrate its capability for both short and continuous fibre reinforced polymer composites, with promising results achieved for the rheological flow and fibre orientation and deformation. View Full-Tex
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