2,146 research outputs found
Detail-preserving and Content-aware Variational Multi-view Stereo Reconstruction
Accurate recovery of 3D geometrical surfaces from calibrated 2D multi-view
images is a fundamental yet active research area in computer vision. Despite
the steady progress in multi-view stereo reconstruction, most existing methods
are still limited in recovering fine-scale details and sharp features while
suppressing noises, and may fail in reconstructing regions with few textures.
To address these limitations, this paper presents a Detail-preserving and
Content-aware Variational (DCV) multi-view stereo method, which reconstructs
the 3D surface by alternating between reprojection error minimization and mesh
denoising. In reprojection error minimization, we propose a novel inter-image
similarity measure, which is effective to preserve fine-scale details of the
reconstructed surface and builds a connection between guided image filtering
and image registration. In mesh denoising, we propose a content-aware
-minimization algorithm by adaptively estimating the value and
regularization parameters based on the current input. It is much more promising
in suppressing noise while preserving sharp features than conventional
isotropic mesh smoothing. Experimental results on benchmark datasets
demonstrate that our DCV method is capable of recovering more surface details,
and obtains cleaner and more accurate reconstructions than state-of-the-art
methods. In particular, our method achieves the best results among all
published methods on the Middlebury dino ring and dino sparse ring datasets in
terms of both completeness and accuracy.Comment: 14 pages,16 figures. Submitted to IEEE Transaction on image
processin
Robust Lasso-Zero for sparse corruption and model selection with missing covariates
We propose Robust Lasso-Zero, an extension of the Lasso-Zero methodology
[Descloux and Sardy, 2018], initially introduced for sparse linear models, to
the sparse corruptions problem. We give theoretical guarantees on the sign
recovery of the parameters for a slightly simplified version of the estimator,
called Thresholded Justice Pursuit. The use of Robust Lasso-Zero is showcased
for variable selection with missing values in the covariates. In addition to
not requiring the specification of a model for the covariates, nor estimating
their covariance matrix or the noise variance, the method has the great
advantage of handling missing not-at random values without specifying a
parametric model. Numerical experiments and a medical application underline the
relevance of Robust Lasso-Zero in such a context with few available
competitors. The method is easy to use and implemented in the R library lass0
NuSTAR observations of the young, energetic radio pulsar PSR B1509-58
We report on Nuclear Spectroscopic Telescope Array (NuSTAR) hard X-ray
observations of the young rotation-powered radio pulsar PSR B150958 in the
supernova remnant MSH 1552. We confirm the previously reported curvature in
the hard X-ray spectrum, showing that a log parabolic model provides a
statistically superior fit to the spectrum compared with the standard power
law. The log parabolic model describes the NuSTAR data, as well as previously
published gamma-ray data obtained with COMPTEL and AGILE, all together spanning
3 keV through 500 MeV. Our spectral modelling allows us to constrain the peak
of the broadband high energy spectrum to be at 2.60.8 MeV, an improvement
of nearly an order of magnitude in precision over previous measurements. In
addition, we calculate NuSTAR spectra in 26 pulse phase bins and confirm
previously reported variations of photon indices with phase. Finally, we
measure the pulsed fraction of PSR B150958 in the hard X-ray energy band for
the first time. Using the energy resolved pulsed fraction results, we estimate
that the pulsar's off-pulse emission has a photon index value between 1.26 and
1.96. Our results support a model in which the pulsar's lack of GeV emission is
due to viewing geometry, with the X-rays originating from synchrotron emission
from secondary pairs in the magnetosphere.Comment: 10 pages, 8 figures, 6 tables, ApJ accepte
Discovery of the Eclipsing Detached Double White Dwarf Binary NLTT 11748
We report the discovery of the first eclipsing detached double white dwarf
(WD) binary. In a pulsation search, the low-mass helium core WD NLTT 11748 was
targeted for fast (approx 1 minute) differential photometry with the Las
Cumbres Observatory's Faulkes Telescope North. Rather than pulsations, we
discovered approx 180 s 3%-6% dips in the photometry. Subsequent radial
velocity measurements of the primary white dwarf from the Keck telescope found
variations with a semi-amplitude K_1 = 271 +/- 3 km/s, and confirmed the dips
as eclipses caused by an orbiting WD with a mass M_2 = 0.648-0.771 M_sun for
M_1 = 0.1-0.2 M_sun. We detect both the primary and secondary eclipses during
the P_orb = 5.64 hr orbit and measure the secondary's brightness to be 3.5% +/-
0.3% of the primary at SDSS-g'. Assuming that the secondary follows the
mass-radius relation of a cold C/O WD and including the effects of microlensing
in the binary, the primary eclipse yields a primary radius of R_1 = 0.043-0.039
R_sun for M_1 = 0.1-0.2 M_sun, consistent with the theoretically expected
values for a helium core WD with a thick, stably burning hydrogen envelope.
Though nearby (at approx 150 pc), the gravitational wave strain from NLTT 11748
is likely not adequate for direct detection by the Laser Interferometer Space
Antenna. Future observational efforts will determine M_1, yielding accurate WD
mass-radius measurement of both components, as well as a clearer indication of
the binary's fate once contact is reached.Comment: 5 pages, 3 figures: Accepted to ApJ Letters, 2010 May 11. v2 corrects
a typo in ephemeris and impliments redline correction
Radio Polarization of the Young High-Magnetic-Field Pulsar PSR J1119-6127
We have investigated the radio polarization properties of PSR J1119-6127, a
recently discovered young radio pulsar with a large magnetic field. Using
pulsar-gated radio imaging data taken at a center frequency of 2496 MHz with
the Australia Telescope Compact Array, we have determined a rotation measure
for the pulsar of +842 +/- 23 rad m^-2. These data, combined with archival
polarimetry data taken at a center frequency of 1366 MHz with the Parkes
telescope, were used to determine the polarization characteristics of PSR
J1119-6127 at both frequencies. The pulsar has a fractional linear polarization
of ~75% and ~55% at 1366 and 2496 MHz, respectively, and the profile consists
of a single, wide component. This pulse morphology and high degree of linear
polarization are in agreement with previously noticed trends for young pulsars
(e.g., PSR J1513-5908). A rotating-vector (RV) model fit of the position angle
(PA) of linear polarization over pulse phase using the Parkes data suggests
that the radio emission comes from the leading edge of a conal beam. We discuss
PSR J1119-6127 in the context of a recent theoretical model of pulsar spin-down
which can in principle be tested with polarization and timing data from this
pulsar. Geometric constraints from the RV fit are currently insufficient to
test this model with statistical significance, but additional data may allow
such a test in the future.Comment: 9 pages, including 6 figures and 1 table. Accepted for publication in
Ap
Detecting Beyond-Einstein Polarizations of Continuous Gravitational Waves
The direct detection of gravitational waves with the next generation
detectors, like Advanced LIGO, provides the opportunity to measure deviations
from the predictions of General Relativity. One such departure would be the
existence of alternative polarizations. To measure these, we study a single
detector measurement of a continuous gravitational wave from a triaxial pulsar
source. We develop methods to detect signals of any polarization content and
distinguish between them in a model independent way. We present LIGO S5
sensitivity estimates for 115 pulsars.Comment: submitted to PR
- …