32,141 research outputs found
The application of KAZE features to the classification echocardiogram videos
In the computer vision field, both approaches of SIFT and SURF are prevalent in the extraction of scale-invariant points and have demonstrated a number of advantages. However, when they are applied to medical images with relevant low contrast between target structures and surrounding regions, these approaches lack the ability to distinguish salient features. Therefore, this research proposes a different approach by extracting feature points using the emerging method of KAZE. As such, to categorise a collection of video images of echocardiograms, KAZE feature points, coupled with three popular representation methods, are addressed in this paper, which includes the bag of words (BOW), sparse coding, and Fisher vector (FV). In comparison with the SIFT features represented using Sparse coding approach that gives 72% overall performance on the classification of eight viewpoints, KAZE feature integrated with either BOW, sparse coding or FV improves the performance significantly with the accuracy being 81.09%, 78.85% and 80.8% respectively. When it comes to distinguish only three primary view locations, 97.44% accuracy can be achieved when employing the approach of KAZE whereas 90% accuracy is realised while applying SIFT features
Long-term monitoring of Molonglo calibrators
Before and after every 12 hour synthesis observation, the Molonglo
Observatory Synthesis Telescope (MOST) measures the flux densities of ~5
compact extragalactic radio sources, chosen from a list of 55 calibrators. From
1984 to 1996, the MOST made some 58 000 such measurements. We have developed an
algorithm to process this dataset to produce a light curve for each source
spanning this thirteen year period. We find that 18 of the 55 calibrators are
variable, on time scales between one and ten years. There is the tendency for
sources closer to the Galactic Plane to be more likely to vary, which suggests
that the variability is a result of refractive scintillation in the Galactic
interstellar medium. The sources with the flattest radio spectra show the
highest levels of variability, an effect possibly resulting from differing
orientations of the radio axes to the line of sight.Comment: 18 pages, 9 embedded EPS files. To appear in Publications of the
Astronomical Society of Australia. Data available electronically at
http://www.physics.usyd.edu.au/astrop/scan
Half metallic digital ferromagnetic heterostructure composed of a -doped layer of Mn in Si
We propose and investigate the properties of a digital ferromagnetic
heterostructure (DFH) consisting of a -doped layer of Mn in Si, using
\textit{ab initio} electronic-structure methods. We find that (i) ferromagnetic
order of the Mn layer is energetically favorable relative to antiferromagnetic,
and (ii) the heterostructure is a two-dimensional half metallic system. The
metallic behavior is contributed by three majority-spin bands originating from
hybridized Mn- and nearest-neighbor Si- states, and the corresponding
carriers are responsible for the ferromagnetic order in the Mn layer. The
minority-spin channel has a calculated semiconducting gap of 0.25 eV. Analysis
of the total and partial densities of states, band structure, Fermi surfaces
and associated charge density reveals the marked two-dimensional nature of the
half metallicity. The band lineup is found to be favorable for retaining the
half metal character to near the Curie temperature (). Being Si based
and possibly having a high as suggested by an experiment on dilutely
doped Mn in Si, the heterostructure may be of special interest for integration
into mature Si technologies for spintronic applications.Comment: 4 pages, 4 figures, Revised version, to appear in Phys. Rev. Let
Photoproduction and Radiative Decay of Spin 1/2 and 3/2 Pentaquarks
We study photoproduction and radiative decays of pentauqarks paying
particular attention to the differences between spin-1/2 and spin-3/2, positive
and negative parities of pentaquarks. Detailed study of these processes can not
only give crucial information about the spin, but also the parity of
pentaquarks.Comment: 14 pages, 7 figure
Berry phase correction to electron density of states in solids
Liouville's theorem on the conservation of phase space volume is violated by
Berry phase in the semiclassical dynamics of Bloch electrons. This leads to a
modification of the phase space density of states, whose significance is
discussed in a number of examples: field modification of the Fermi-sea volume,
connection to the anomalous Hall effect, and a general formula for orbital
magnetization. The effective quantum mechanics of Bloch electrons is also
sketched, where the modified density of states plays an essential role.Comment: Minor revision. Journal info updat
The two-loop supersymmetric corrections to lepton anomalous magnetic and electric dipole moments
Using the effective Lagrangian method, we analyze the electroweak corrections
to the anomalous dipole moments of lepton from some special two-loop
topological diagrams which are composed of neutralino (chargino) - slepton
(sneutrino) in the minimal supersymmetric extension of the standard model
(MSSM). Considering the translational invariance of the inner loop momenta and
the electromagnetic gauge invariance, we get all dimension 6 operators and
derive their coefficients. After applying equations of motion to the external
leptons, the anomalous dipole moments of lepton are obtained. The numerical
results imply that there is a parameter space where the two-loop supersymmetric
corrections to the muon anomalous dipole moments may be significant.Comment: Revtex, 45 pages, including 8 fig
Geometric properties of two-dimensional O(n) loop configurations
We study the fractal geometry of O() loop configurations in two dimensions
by means of scaling and a Monte Carlo method, and compare the results with
predictions based on the Coulomb gas technique. The Monte Carlo algorithm is
applicable to models with noninteger and uses local updates. Although these
updates typically lead to nonlocal modifications of loop connectivities, the
number of operations required per update is only of order one. The Monte Carlo
algorithm is applied to the O() model for several values of , including
noninteger ones. We thus determine scaling exponents that describe the fractal
nature of O() loops at criticality. The results of the numerical analysis
agree with the theoretical predictions.Comment: 18 pages, 6 figure
Gravity-based models for evaluating urban park accessibility: Why does localized selection of attractiveness factors and travel modes matter?
Gravity-based models have been extensively utilized in urban studies for measuring geographic disparities in access to urban parks over the past several decades. However, despite methodological advancements incorporating various aspects of accessibility, there has been limited focus on the impact of variable selection (e.g., attractiveness factors) and transport modes on accessibility evaluations. This study investigates the differences in gravity-based models for assessing park accessibility based on varying assumptions about attractiveness factors and travel impedance. Semi-structured interviews with local residents were conducted to identify the reasons for park visits in Shanghai. Our bivariate correlation analyses reveal that factors such as park openness and access to public transport were crucial, in addition to conventional factors identified in the literature (i.e., park size and driving accessibility). This insight led to the development of localized accessibility measurements that incorporate park inclusiveness (i.e., entrance fees and opening hours) and multimodal travel options (based on multinomial logistic mode choice models). The results indicate that the refined model produces lower and more varied accessibility levels, which can better capture accessibility gaps across different geographic contexts. This accurate and practical identification of accessibility gaps can assist local planners and decision-makers in formulating effective policies and strategies to promote equitable access to urban public parks
Phase Diagram of Rydberg atoms in a nonequilibrium optical lattice
We study the quantum nonequilibrium dynamics of ultracold three-level atoms
trapped in an optical lattice, which are excited to their Rydberg states via a
two-photon excitation with nonnegligible spontaneous emission. Rich quantum
phases including uniform phase, antiferromagnetic phase and oscillatory phase
are identified. We map out the phase diagram and find these phases can be
controlled by adjusting the ratio of intensity of the pump light to the control
light, and that of two-photon detuning to the Rydberg interaction strength.
When the two-photon detuning is blue-shifted and the latter ratio is less than
1, bistability exists among the phases. Actually, this ratio controls the
Rydberg-blockade and antiblockade effect, thus the phase transition in this
system can be considered as a possible approach to study both effects.Comment: 5 pages,5 figure
Semimetal to semimetal charge density wave transition in 1T-TiSe
We report an infrared study on 1-TiSe, the parent compound of the
newly discovered superconductor CuTiSe. Previous studies of this
compound have not conclusively resolved whether it is a semimetal or a
semiconductor: information that is important in determining the origin of its
unconventional CDW transition. Here we present optical spectroscopy results
that clearly reveal that the compound is metallic in both the high-temperature
normal phase and the low-temperature CDW phase. The carrier scattering rate is
dramatically different in the normal and CDW phases and the carrier density is
found to change with temperature. We conclude that the observed properties can
be explained within the scenario of an Overhauser-type CDW mechanism.Comment: 4 pages, 4 page
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