49,616 research outputs found
Deep Self-Taught Learning for Weakly Supervised Object Localization
Most existing weakly supervised localization (WSL) approaches learn detectors
by finding positive bounding boxes based on features learned with image-level
supervision. However, those features do not contain spatial location related
information and usually provide poor-quality positive samples for training a
detector. To overcome this issue, we propose a deep self-taught learning
approach, which makes the detector learn the object-level features reliable for
acquiring tight positive samples and afterwards re-train itself based on them.
Consequently, the detector progressively improves its detection ability and
localizes more informative positive samples. To implement such self-taught
learning, we propose a seed sample acquisition method via image-to-object
transferring and dense subgraph discovery to find reliable positive samples for
initializing the detector. An online supportive sample harvesting scheme is
further proposed to dynamically select the most confident tight positive
samples and train the detector in a mutual boosting way. To prevent the
detector from being trapped in poor optima due to overfitting, we propose a new
relative improvement of predicted CNN scores for guiding the self-taught
learning process. Extensive experiments on PASCAL 2007 and 2012 show that our
approach outperforms the state-of-the-arts, strongly validating its
effectiveness.Comment: Accepted as spotlight paper by CVPR 201
Adaptive Deep Learning through Visual Domain Localization
A commercial robot, trained by its manufacturer to recognize a predefined number and type of objects, might be used in many settings, that will in general differ in their illumination conditions, background, type and degree of clutter, and so on. Recent computer vision works tackle this generalization issue through domain adaptation methods, assuming as source the visual domain where the system is trained and as target the domain of deployment. All approaches assume to have access to images from all classes of the target during training, an unrealistic condition in robotics applications. We address this issue proposing an algorithm that takes into account the specific needs of robot vision. Our intuition is that the nature of the domain shift experienced mostly in robotics is local. We exploit this through the learning of maps that spatially ground the domain and quantify the degree of shift, embedded into an end-to-end deep domain adaptation architecture. By explicitly localizing the roots of the domain shift we significantly reduce the number of parameters of the architecture to tune, we gain the flexibility necessary to deal with subset of categories in the target domain at training time, and we provide a clear feedback on the rationale behind any classification decision, which can be exploited in human-robot interactions. Experiments on two different settings of the iCub World database confirm the suitability of our method for robot vision
Insulator-Metal Transition in the One and Two-Dimensional Hubbard Models
We use Quantum Monte Carlo methods to determine Green functions,
, on lattices up to for the 2D Hubbard model
at . For chemical potentials, , within the Hubbard gap, , and at {\it long} distances, , with critical behavior: , . This result stands in agreement with the
assumption of hyperscaling with correlation exponent and dynamical
exponent . In contrast, the generic band insulator as well as the
metal-insulator transition in the 1D Hubbard model are characterized by and .Comment: 9 pages (latex) and 5 postscript figures. Submitted for publication
in Phys. Rev. Let
Keypoint Transfer for Fast Whole-Body Segmentation
We introduce an approach for image segmentation based on sparse
correspondences between keypoints in testing and training images. Keypoints
represent automatically identified distinctive image locations, where each
keypoint correspondence suggests a transformation between images. We use these
correspondences to transfer label maps of entire organs from the training
images to the test image. The keypoint transfer algorithm includes three steps:
(i) keypoint matching, (ii) voting-based keypoint labeling, and (iii)
keypoint-based probabilistic transfer of organ segmentations. We report
segmentation results for abdominal organs in whole-body CT and MRI, as well as
in contrast-enhanced CT and MRI. Our method offers a speed-up of about three
orders of magnitude in comparison to common multi-atlas segmentation, while
achieving an accuracy that compares favorably. Moreover, keypoint transfer does
not require the registration to an atlas or a training phase. Finally, the
method allows for the segmentation of scans with highly variable field-of-view.Comment: Accepted for publication at IEEE Transactions on Medical Imagin
Quantum-state transfer in staggered coupled-cavity arrays
We consider a coupled-cavity array, where each cavity interacts with an atom
under the rotating-wave approximation. For a staggered pattern of inter-cavity
couplings, a pair of field normal modes each bi-localized at the two array ends
arise. A rich structure of dynamical regimes can hence be addressed depending
on which resonance condition between the atom and field modes is set. We show
that this can be harnessed to carry out high-fidelity quantum-state transfer
(QST) of photonic, atomic or polaritonic states. Moreover, by partitioning the
array into coupled modules of smaller length, the QST time can be substantially
shortened without significantly affecting the fidelity.Comment: 12 pages, 8 figure
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