20 research outputs found
TernausNetV2: Fully Convolutional Network for Instance Segmentation
The most common approaches to instance segmentation are complex and use
two-stage networks with object proposals, conditional random-fields, template
matching or recurrent neural networks. In this work we present TernausNetV2 - a
simple fully convolutional network that allows extracting objects from a
high-resolution satellite imagery on an instance level. The network has popular
encoder-decoder type of architecture with skip connections but has a few
essential modifications that allows using for semantic as well as for instance
segmentation tasks. This approach is universal and allows to extend any network
that has been successfully applied for semantic segmentation to perform
instance segmentation task. In addition, we generalize network encoder that was
pre-trained for RGB images to use additional input channels. It makes possible
to use transfer learning from visual to a wider spectral range. For
DeepGlobe-CVPR 2018 building detection sub-challenge, based on public
leaderboard score, our approach shows superior performance in comparison to
other methods. The source code corresponding pre-trained weights are publicly
available at https://github.com/ternaus/TernausNetV
Superconducting Transitions in Flat Band Systems
The physics of strongly correlated quantum particles within a flat band was
originally explored as a route to itinerant ferromagnetism and, indeed, a
celebrated theorem by Lieb rigorously establishes that the ground state of the
repulsive Hubbard model on a bipartite lattice with unequal number of sites in
each sublattice must have nonzero spin S at half-filling. Recently, there has
been interest in Lieb geometries due to the possibility of novel topological
insulator, nematic, and Bose-Einstein condensed (BEC) phases. In this paper, we
extend the understanding of the attractive Hubbard model on the Lieb lattice by
using Determinant Quantum Monte Carlo to study real space charge and pair
correlation functions not addressed by the Lieb theorems
Feature Pyramid Network for Multi-Class Land Segmentation
Semantic segmentation is in-demand in satellite imagery processing. Because
of the complex environment, automatic categorization and segmentation of land
cover is a challenging problem. Solving it can help to overcome many obstacles
in urban planning, environmental engineering or natural landscape monitoring.
In this paper, we propose an approach for automatic multi-class land
segmentation based on a fully convolutional neural network of feature pyramid
network (FPN) family. This network is consisted of pre-trained on ImageNet
Resnet50 encoder and neatly developed decoder. Based on validation results,
leaderboard score and our own experience this network shows reliable results
for the DEEPGLOBE - CVPR 2018 land cover classification sub-challenge.
Moreover, this network moderately uses memory that allows using GTX 1080 or
1080 TI video cards to perform whole training and makes pretty fast
predictions
2018 Robotic Scene Segmentation Challenge
In 2015 we began a sub-challenge at the EndoVis workshop at MICCAI in Munich using endoscope images of ex-vivo tissue with automatically generated annotations from robot forward kinematics and instrument CAD models. However, the limited background variation and simple motion rendered the dataset uninformative in learning about which techniques would be suitable for segmentation in real surgery. In 2017, at the same workshop in Quebec we introduced the robotic instrument segmentation dataset with 10 teams participating in the challenge to perform binary, articulating parts and type segmentation of da Vinci instruments. This challenge included realistic instrument motion and more complex porcine tissue as background and was widely addressed with modifications on U-Nets and other popular CNN architectures. In 2018 we added to the complexity by introducing a set of anatomical objects and medical devices to the segmented classes. To avoid over-complicating the challenge, we continued with porcine data which is dramatically simpler than human tissue due to the lack of fatty tissue occluding many organs
Geometry dependence of the sign problem in quantum Monte Carlo simulations
The sign problem is the fundamental limitation to quantum Monte Carlo simulations of the statistical mechanics of interacting fermions. Determinant quantum Monte Carlo (DQMC) is one of the leading methods to study lattice fermions, such as the Hubbard Hamiltonian, which describe strongly correlated phenomena including magnetism, metal-insulator transitions, and possibly exotic superconductivity. Here, we provide a comprehensive dataset on the geometry dependence of the DQMC sign problem for different densities, interaction strengths, temperatures, and spatial lattice sizes. We supplement these data with several observations concerning general trends in the data, including the dependence on spatial volume and how this can be probed by examining decoupled clusters, the scaling of the sign in the vicinity of a particle-hole symmetric point, and the correlation between the total sign and the signs for the individual spin species