269,446 research outputs found
Multitraining support vector machine for image retrieval
Relevance feedback (RF) schemes based on support vector machines (SVMs) have been widely used in content-based image retrieval (CBIR). However, the performance of SVM-based RF approaches is often poor when the number of labeled feedback samples is small. This is mainly due to 1) the SVM classifier being unstable for small-size training sets because its optimal hyper plane is too sensitive to the training examples; and 2) the kernel method being ineffective because the feature dimension is much greater than the size of the training samples. In this paper, we develop a new machine learning technique, multitraining SVM (MTSVM), which combines the merits of the cotraining technique and a random sampling method in the feature space. Based on the proposed MTSVM algorithm, the above two problems can be mitigated. Experiments are carried out on a large image set of some 20 000 images, and the preliminary results demonstrate that the developed method consistently improves the performance over conventional SVM-based RFs in terms of precision and standard deviation, which are used to evaluate the effectiveness and robustness of a RF algorithm, respectively
Relativistic description of magnetic moments in nuclei with doubly closed shells plus or minus one nucleon
Using the relativistic point-coupling model with density functional PC-PK1,
the magnetic moments of the nuclei Pb, Pb, Tl and
Bi with a closed-shell core Pb are studied on the basis of
relativistic mean field (RMF) theory. The corresponding time-odd fields, the
one-pion exchange currents, and the first- and second-order corrections are
taken into account. The present relativistic results reproduce the data well.
The relative deviation between theory and experiment for these four nuclei is
6.1% for the relativistic calculations and somewhat smaller than the value of
13.2% found in earlier non-relativistic investigations. It turns out that the
meson is important for the description of magnetic moments, first by
means of one-pion exchange currents and second by the residual interaction
provided by the exchange.Comment: 11 pages, 7 figure
Cavity Mode Frequencies and Strong Optomechanical Coupling in Two-Membrane Cavity Optomechanics
We study the cavity mode frequencies of a Fabry-P\'erot cavity containing two
vibrating dielectric membranes. We derive the equations for the mode resonances
and provide approximate analytical solutions for them as a function of the
membrane positions, which act as an excellent approximation when the relative
and center-of-mass position of the two membranes are much smaller than the
cavity length. With these analytical solutions, one finds that extremely large
optomechanical coupling of the membrane relative motion can be achieved in the
limit of highly reflective membranes when the two membranes are placed very
close to a resonance of the inner cavity formed by them. We also study the
cavity finesse of the system and verify that, under the conditions of large
coupling, it is not appreciably affected by the presence of the two membranes.
The achievable large values of the ratio between the optomechanical coupling
and the cavity decay rate, , make this two-membrane system the
simplest promising platform for implementing cavity optomechanics in the strong
coupling regime.Comment: Contribution to the special issue on "Nano-optomechanics" in Journal
of Optics, edited by I. Wilson-Rae, J. Sankey and H. Offerhau
Ratcheting Heat Flux against a Thermal Bias
Merely rocking the temperature in one heat bath can direct a steady heat flux
from cold to hot against a non-zero thermal bias in stylized nonlinear lattice
junctions that are sandwiched between two heat baths. Likewise, for an average
zero-temperature difference between the two contacts a net, ratchet-like heat
flux emerges. Computer simulations show that this very heat flux can be
controlled and reversed by suitably tailoring the frequency ( 100
MHz) of the alternating temperature field.Comment: 5 pages, 6 figure
Unusual Nernst effect suggestive of time-reversal violation in the striped cuprate LaBaCuO
The striped cuprate LaBaCuO ( undergoes several
transitions below the charge-ordering temperature = 54 K. From Nernst
experiments, we find that, below , there exists a large, anomalous
Nernst signal that is symmetric in field , and remains
finite as . The time-reversal violating signal suggests that, below
, vortices of one sign are spontaneously created to relieve interlayer
phase frustration.Comment: 5 pages, 4 figure
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