59,444 research outputs found
Tracking-Based Non-Parametric Background-Foreground Classification in a Chromaticity-Gradient Space
This work presents a novel background-foreground classification technique based on adaptive non-parametric kernel estimation in a color-gradient space of components. By combining normalized color components with their gradients, shadows are efficiently suppressed from the results, while the luminance information in the moving objects is preserved. Moreover, a fast multi-region iterative tracking strategy applied over previously detected foreground regions allows to construct a robust foreground modeling, which combined with the background model increases noticeably the quality in the detections. The proposed strategy has been applied to different kind of sequences, obtaining satisfactory results in complex situations such as those given by dynamic backgrounds, illumination changes, shadows and multiple moving objects
Computation of Light Scattering in Young Stellar Objects
A Monte Carlo light scattering code incorporating aligned non-spherical
particles is described. The major effects on the flux distribution, linear
polarisation and circular polarisation are presented, with emphasis on the
application to Young Stellar Objects (YSOs). The need for models with
non-spherical particles in order to successfully model polarisation data is
reviewed. The ability of this type of model to map magnetic field structure in
embedded YSOs is described. The possible application to the question of the
origin of biomolecular homochirality via UV circular polarisation in star
forming regions is also briefly discussed.Comment: Accepted by The Journal of Quantitative Spectroscopy and Radiative
Transfer. Replaced version corrects an error in the definition of the sense
of Cpol in the published version and other minor errors found at the proof
stag
Semantic Object Parsing with Local-Global Long Short-Term Memory
Semantic object parsing is a fundamental task for understanding objects in
detail in computer vision community, where incorporating multi-level contextual
information is critical for achieving such fine-grained pixel-level
recognition. Prior methods often leverage the contextual information through
post-processing predicted confidence maps. In this work, we propose a novel
deep Local-Global Long Short-Term Memory (LG-LSTM) architecture to seamlessly
incorporate short-distance and long-distance spatial dependencies into the
feature learning over all pixel positions. In each LG-LSTM layer, local
guidance from neighboring positions and global guidance from the whole image
are imposed on each position to better exploit complex local and global
contextual information. Individual LSTMs for distinct spatial dimensions are
also utilized to intrinsically capture various spatial layouts of semantic
parts in the images, yielding distinct hidden and memory cells of each position
for each dimension. In our parsing approach, several LG-LSTM layers are stacked
and appended to the intermediate convolutional layers to directly enhance
visual features, allowing network parameters to be learned in an end-to-end
way. The long chains of sequential computation by stacked LG-LSTM layers also
enable each pixel to sense a much larger region for inference benefiting from
the memorization of previous dependencies in all positions along all
dimensions. Comprehensive evaluations on three public datasets well demonstrate
the significant superiority of our LG-LSTM over other state-of-the-art methods.Comment: 10 page
Polycaprolactone-based, porous CaCO3 and Ag nanoparticle modified scaffolds as a SERS platform with molecule-specific adsorption
Surface-enhanced Raman scattering (SERS) is a high-performance technique allowing detection of extremely low concentrations of analytes. For such applications, fibrous polymeric matrices decorated with plasmonic metal nanostructures can be used as flexible SERS substrates for analysis of analytes in many application. In this study, a three-dimensional SERS substrate consisting of a CaCO3-mineralized electrospun (ES) polycaprolactone (PCL) fibrous matrix decorated with silver (Ag) nanoparticles is developed. Such modification of the fibrous substrate allows achieving a significant increase of the SERS signal amplification. Functionalization of fibers by porous CaCO3 (vaterite) and Ag nanoparticles provides an effective approach of selective adsorption of biomolecules and their precise detection by SERS. This new SERS substrate represents a promising biosensor platform with selectivity to low and high molecular weight molecules
Mitigation of Through-Wall Distortions of Frontal Radar Images using Denoising Autoencoders
Radar images of humans and other concealed objects are considerably distorted
by attenuation, refraction and multipath clutter in indoor through-wall
environments. While several methods have been proposed for removing target
independent static and dynamic clutter, there still remain considerable
challenges in mitigating target dependent clutter especially when the knowledge
of the exact propagation characteristics or analytical framework is
unavailable. In this work we focus on mitigating wall effects using a machine
learning based solution -- denoising autoencoders -- that does not require
prior information of the wall parameters or room geometry. Instead, the method
relies on the availability of a large volume of training radar images gathered
in through-wall conditions and the corresponding clean images captured in
line-of-sight conditions. During the training phase, the autoencoder learns how
to denoise the corrupted through-wall images in order to resemble the free
space images. We have validated the performance of the proposed solution for
both static and dynamic human subjects. The frontal radar images of static
targets are obtained by processing wideband planar array measurement data with
two-dimensional array and range processing. The frontal radar images of dynamic
targets are simulated using narrowband planar array data processed with
two-dimensional array and Doppler processing. In both simulation and
measurement processes, we incorporate considerable diversity in the target and
propagation conditions. Our experimental results, from both simulation and
measurement data, show that the denoised images are considerably more similar
to the free-space images when compared to the original through-wall images
Structural graph matching using the EM algorithm and singular value decomposition
This paper describes an efficient algorithm for inexact graph matching. The method is purely structural, that is, it uses only the edge or connectivity structure of the graph and does not draw on node or edge attributes. We make two contributions: 1) commencing from a probability distribution for matching errors, we show how the problem of graph matching can be posed as maximum-likelihood estimation using the apparatus of the EM algorithm; and 2) we cast the recovery of correspondence matches between the graph nodes in a matrix framework. This allows one to efficiently recover correspondence matches using the singular value decomposition. We experiment with the method on both real-world and synthetic data. Here, we demonstrate that the method offers comparable performance to more computationally demanding method
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