12 research outputs found
SBNet: Sparse Blocks Network for Fast Inference
Conventional deep convolutional neural networks (CNNs) apply convolution
operators uniformly in space across all feature maps for hundreds of layers -
this incurs a high computational cost for real-time applications. For many
problems such as object detection and semantic segmentation, we are able to
obtain a low-cost computation mask, either from a priori problem knowledge, or
from a low-resolution segmentation network. We show that such computation masks
can be used to reduce computation in the high-resolution main network. Variants
of sparse activation CNNs have previously been explored on small-scale tasks
and showed no degradation in terms of object classification accuracy, but often
measured gains in terms of theoretical FLOPs without realizing a practical
speed-up when compared to highly optimized dense convolution implementations.
In this work, we leverage the sparsity structure of computation masks and
propose a novel tiling-based sparse convolution algorithm. We verified the
effectiveness of our sparse CNN on LiDAR-based 3D object detection, and we
report significant wall-clock speed-ups compared to dense convolution without
noticeable loss of accuracy.Comment: 10 pages, CVPR 201
Exploiting Sparse Semantic HD Maps for Self-Driving Vehicle Localization
In this paper we propose a novel semantic localization algorithm that
exploits multiple sensors and has precision on the order of a few centimeters.
Our approach does not require detailed knowledge about the appearance of the
world, and our maps require orders of magnitude less storage than maps utilized
by traditional geometry- and LiDAR intensity-based localizers. This is
important as self-driving cars need to operate in large environments. Towards
this goal, we formulate the problem in a Bayesian filtering framework, and
exploit lanes, traffic signs, as well as vehicle dynamics to localize robustly
with respect to a sparse semantic map. We validate the effectiveness of our
method on a new highway dataset consisting of 312km of roads. Our experiments
show that the proposed approach is able to achieve 0.05m lateral accuracy and
1.12m longitudinal accuracy on average while taking up only 0.3% of the storage
required by previous LiDAR intensity-based approaches.Comment: 8 pages, 4 figures, 4 tables, 2019 IEEE/RSJ International Conference
on Intelligent Robots and Systems (IROS 2019
Elastic theory of flux lattices in presence of weak disorder
The effect of disorder on flux lattices at equilibrium is studied
quantitatively in the absence of free dislocations using both the Gaussian
variational method and the renormalization group. Our results for the mean
square relative displacements clarify the nature of the crossovers with
distance. We find three regimes: (i) a short distance regime (``Larkin
regime'') where elasticity holds (ii) an intermediate regime (``Random
Manifold'') where vortices are pinned independently (iii) a large distance,
quasi-ordered regime where the periodicity of the lattice becomes important and
there is universal logarithmic growth of displacements for and
persistence of algebraic quasi-long range translational order. The functional
renormalization group to and the variational method, agree
within on the value of the exponent. In we compute the crossover
function between the three regimes. We discuss the observable signature of this
crossover in decoration experiments and in neutron diffraction experiments on
flux lattices. Qualitative arguments are given suggesting the existence for
weak disorder in of a `` Bragg glass '' phase without free dislocations
and with algebraically divergent Bragg peaks. In both the variational
method and the Cardy-Ostlund renormalization group predict a glassy state below
the same transition temperature , but with different behaviors.
Applications to systems and experiments on magnetic bubbles are
discussed.Comment: 59 pages; RevTeX 3.0; 5 postscript figures uuencode
Moving glass theory of driven lattices with disorder
We study periodic structures, such as vortex lattices, moving in a random
potential. As predicted in [T. Giamarchi, P. Le Doussal Phys. Rev. Lett. 76
3408 (1996)] the periodicity in the direction transverse to motion leads to a
new class of driven systems: the Moving Glasses. We analyse using several RG
techniques the properties at T=0 and : (i) decay of translational long
range order (ii) particles flow along static channels (iii) the channel pattern
is highly correlated (iv) barriers to transverse motion. We demonstrate the
existence of the ``transverse critical force'' at T=0. A ``static random
force'' is shown to be generated by motion. Displacements grow logarithmically
in and algebraically in . The persistence of quasi long range
translational order in at weak disorder, or large velocity leads to
predict a topologically ordered ``Moving Bragg Glass''. This state continues
the static Bragg glass and is stable at , with non linear transverse
response and linear asymptotic behavior. In , or in at intermediate
disorder, another moving glass exist (the Moving Transverse Glass) with smectic
quasi order in the transverse direction. A phase diagram in force and
disorder for static and moving structures is proposed. For correlated disorder
we predict a ``moving Bose glass'' state with anisotropic transverse Meissner
effect and transverse pinning. We discuss experimental consequences such as
anomalous Hall effect in Wigner crystal and transverse critical current in
vortex lattice.Comment: 74 pages, 27 figures, RevTe
Biological Earth observation with animal sensors
Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change
Extreme biomimetics: Preservation of molecular detail in centimeter-scale samples of biological meshes laid down by sponges
International audienceFabrication of biomimetic materials and scaffolds is usually a micro- or even nanoscale process; however, most testing and all manufacturing require larger-scale synthesis of nanoscale features. Here, we propose the utilization of naturally prefabricated three-dimensional (3D) spongin scaffolds that preserve molecular detail across centimeter-scale samples. The fine-scale structure of this collagenous resource is stable at temperatures of up to 1200°C and can produce up to 4 × 10–cm–large 3D microfibrous and nanoporous turbostratic graphite. Our findings highlight the fact that this turbostratic graphite is exceptional at preserving the nanostructural features typical for triple-helix collagen. The resulting carbon sponge resembles the shape and unique microarchitecture of the original spongin scaffold. Copper electroplating of the obtained composite leads to a hybrid material with excellent catalytic performance with respect to the reduction of p-nitrophenol in both freshwater and marine environments
Tunable Plasmonic Properties and Absorption Enhancement in Terahertz Photoconductive Antenna Based on Optimized Plasmonic Nanostructures
Herein, we numerically investigate terahertz photoconductive antennas (PCAs) based on optimized plasmonic nanostructures and absorption enhancement in nanocylinders. Plasmonic behavior in the visible to near-infrared light spectrum is achievable due to the metallic nanostructure employment. Herein, we study the absorption enhancement of silver and transparent-conducting oxides (TCO) nanocylinders with different diameters by means of effective medium approximation. This study also reports on the stronger enhancement in the case of TCO nanocylinders. The results show that resonant absorption amplitude and wavelength are dramatically affected by the thickness of the nanostructure as well as by the distances between nanocylinders. The outputs reported here provide a fertile ground for precise control of the nanowire structures for sensing and other enhanced optical applications. It is worthwhile noting that in case of TCO nanocylinders, absorption enhancement for NIR wavelengths, being relevant for present terahertz generation setup, reaches up to fivefold leading to 25-fold increase in terahertz radiation