125,462 research outputs found
S-OHEM: Stratified Online Hard Example Mining for Object Detection
One of the major challenges in object detection is to propose detectors with
highly accurate localization of objects. The online sampling of high-loss
region proposals (hard examples) uses the multitask loss with equal weight
settings across all loss types (e.g, classification and localization, rigid and
non-rigid categories) and ignores the influence of different loss distributions
throughout the training process, which we find essential to the training
efficacy. In this paper, we present the Stratified Online Hard Example Mining
(S-OHEM) algorithm for training higher efficiency and accuracy detectors.
S-OHEM exploits OHEM with stratified sampling, a widely-adopted sampling
technique, to choose the training examples according to this influence during
hard example mining, and thus enhance the performance of object detectors. We
show through systematic experiments that S-OHEM yields an average precision
(AP) improvement of 0.5% on rigid categories of PASCAL VOC 2007 for both the
IoU threshold of 0.6 and 0.7. For KITTI 2012, both results of the same metric
are 1.6%. Regarding the mean average precision (mAP), a relative increase of
0.3% and 0.5% (1% and 0.5%) is observed for VOC07 (KITTI12) using the same set
of IoU threshold. Also, S-OHEM is easy to integrate with existing region-based
detectors and is capable of acting with post-recognition level regressors.Comment: 9 pages, 3 figures, accepted by CCCV 201
Quark Recombination and Heavy Quark Diffusion in Hot Nuclear Matter
We discuss resonance recombination for quarks and show that it is compatible
with quark and hadron distributions in local thermal equilibrium. We then
calculate realistic heavy quark phase space distributions in heavy ion
collisions using Langevin simulations with non-perturbative T-matrix
interactions in hydrodynamic backgrounds. We hadronize the heavy quarks on the
critical hypersurface given by hydrodynamics after constructing a criterion for
the relative recombination and fragmentation contributions. We discuss the
influence of recombination and flow on the resulting heavy meson and single
electron R_AA and elliptic flow. We will also comment on the effect of
diffusion of open heavy flavor mesons in the hadronic phase.Comment: Contribution to Quark Matter 2011, submitted to J.Phys.G; 4 pages, 5
figure
Convolutional Networks for Object Category and 3D Pose Estimation from 2D Images
Current CNN-based algorithms for recovering the 3D pose of an object in an
image assume knowledge about both the object category and its 2D localization
in the image. In this paper, we relax one of these constraints and propose to
solve the task of joint object category and 3D pose estimation from an image
assuming known 2D localization. We design a new architecture for this task
composed of a feature network that is shared between subtasks, an object
categorization network built on top of the feature network, and a collection of
category dependent pose regression networks. We also introduce suitable loss
functions and a training method for the new architecture. Experiments on the
challenging PASCAL3D+ dataset show state-of-the-art performance in the joint
categorization and pose estimation task. Moreover, our performance on the joint
task is comparable to the performance of state-of-the-art methods on the
simpler 3D pose estimation with known object category task
Scales of Fermion Mass Generation and Electroweak Symmetry Breaking
The scale of mass generation for fermions (including neutrinos) and the scale
for electroweak symmetry breaking (EWSB) can be bounded from above by the
unitarity of scattering involving longitudinal weak gauge bosons or their
corresponding would-be Goldstone bosons. Including the exact n-body phase space
we analyze the 2 --> n () processes for the fermion-(anti)fermion
scattering into multiple gauge boson final states. Contrary to naive energy
power counting, we demonstrate that as becomes large, the competition
between an increasing energy factor and a phase-space suppression leads to a
{\it strong new upper bound} on the scale of fermion mass generation at a
finite value , which is {\it independent of the EWSB scale,} . For quarks, leptons and Majorana neutrinos, the
strongest 2 --> n limits range from about 3TeV to 130-170TeV (with ), depending on the measured fermion masses. Strikingly, given
the tiny neutrino masses as constrained by the neutrino oscillations,
neutrinoless double-beta decays and astrophysical observations, the unitarity
violation of scattering actually occurs at a scale no
higher than ~170 TeV. Implications for various mechanisms of neutrino mass
generation are analyzed. On the other hand, for the 2 --> n pure
Goldstone-boson scattering, we find that the decreasing phase space factor
always dominates over the growing overall energy factor when becomes large,
so that the best unitarity bound on the scale of EWSB remains at n=2.Comment: 67pp, to match PRD (minor typos fixed
The Reactivity of MgB2 with Common Substrate and Electronic Materials
The reactivity of MgB2 with powdered forms of common substrate and electronic
materials is reported. Reaction temperatures between 600 C and 800 C,
encompassing the range commonly employed in thin-film fabrication, were
studied. The materials tested for reactivity were ZrO2, yttria stabilized
zirconia (YSZ), MgO, Al2O3, SiO2, SrTiO3, TiN, TaN, AlN, Si, and SiC. At 600 C,
MgB2 reacted only with SiO2 and Si. At 800 C, however, reactions were observed
for MgB2 with Al2O3, SiO2, Si, SiC, and SrTiO3. The Tc of MgB2 decreased in the
reactions with SiC and Al2O3.Comment: 5 figure
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