241 research outputs found
Collaborative Feature Learning from Social Media
Image feature representation plays an essential role in image recognition and
related tasks. The current state-of-the-art feature learning paradigm is
supervised learning from labeled data. However, this paradigm requires
large-scale category labels, which limits its applicability to domains where
labels are hard to obtain. In this paper, we propose a new data-driven feature
learning paradigm which does not rely on category labels. Instead, we learn
from user behavior data collected on social media. Concretely, we use the image
relationship discovered in the latent space from the user behavior data to
guide the image feature learning. We collect a large-scale image and user
behavior dataset from Behance.net. The dataset consists of 1.9 million images
and over 300 million view records from 1.9 million users. We validate our
feature learning paradigm on this dataset and find that the learned feature
significantly outperforms the state-of-the-art image features in learning
better image similarities. We also show that the learned feature performs
competitively on various recognition benchmarks
Variable bandwidth kernel regression estimation
In this paper we propose a variable bandwidth kernel regression estimator for
observations in to improve the classical
Nadaraya-Watson estimator. The bias is improved to the order of
under the condition that the fifth order derivative of the density function and
the sixth order derivative of the regression function are bounded and
continuous. We also establish the central limit theorems for the proposed ideal
and true variable kernel regression estimators. The simulation study confirms
our results and demonstrates the advantage of the variable bandwidth kernel
method over the classical kernel method.Comment: accepted by ESAIM: PS. 36 pages, 3 figure
Low-field magnetotransport in graphene cavity devices
Confinement and edge structures are known to play significant roles in
electronic and transport properties of two-dimensional materials. Here, we
report on low-temperature magnetotransport measurements of lithographically
patterned graphene cavity nanodevices. It is found that the evolution of the
low-field magnetoconductance characteristics with varying carrier density
exhibits different behaviors in graphene cavity and bulk graphene devices. In
the graphene cavity devices, we have observed that intravalley scattering
becomes dominant as the Fermi level gets close to the Dirac point. We associate
this enhanced intravalley scattering to the effect of charge inhomogeneities
and edge disorder in the confined graphene nanostructures. We have also
observed that the dephasing rate of carriers in the cavity devices follows a
parabolic temperature dependence, indicating that the direct Coulomb
interaction scattering mechanism governs the dephasing at low temperatures. Our
results demonstrate the importance of confinement in carrier transport in
graphene nanostructure devices.Comment: 13 pages, 5 figure
Charge transport and electron-hole asymmetry in low-mobility graphene/hexagonal boron nitride heterostructures
Graphene/hexagonal boron nitride (G/-BN) heterostructures offer an
excellent platform for developing nanoelectronic devices and for exploring
correlated states in graphene under modulation by a periodic superlattice
potential. Here, we report on transport measurements of nearly
-twisted G/-BN heterostructures. The heterostructures
investigated are prepared by dry transfer and thermally annealing processes and
are in the low mobility regime (approximately
at 1.9 K). The replica
Dirac spectra and Hofstadter butterfly spectra are observed on the hole
transport side, but not on the electron transport side, of the
heterostructures. We associate the observed electron-hole asymmetry to the
presences of a large difference between the opened gaps in the conduction and
valence bands and a strong enhancement in the interband contribution to the
conductivity on the electron transport side in the low-mobility G/-BN
heterostructures. We also show that the gaps opened at the central Dirac point
and the hole-branch secondary Dirac point are large, suggesting the presence of
strong graphene-substrate interaction and electron-electron interaction in our
G/-BN heterostructures. Our results provide additional helpful insight into
the transport mechanism in G/-BN heterostructures.Comment: 7 pages, 4 figure
Further refinement of self-normalized Cramér-type moderate deviations
In this paper, we study the self-normalized Cramér-type moderate deviations for centered independent random variables X1,X2,... with 0 <E | Xi | 3< ∞. The main results refine Theorems 1.1 and 1.2 of Wang [Q. Wang, J. Theoret. Probab. 24 (2011) 307–329], the Berry−Esseen bound (2.11) and Corollaries 2.2 and 2.3 of Jing, et al. [B.Y. Jing, Q.M. Shao and Q. Wang, Ann. Probab. 31 (2003) 2167–2215] under stronger moment conditions
ALADIN: All Layer Adaptive Instance Normalization for Fine-grained Style Similarity
We present ALADIN (All Layer AdaIN); a novel architecture for searching
images based on the similarity of their artistic style. Representation learning
is critical to visual search, where distance in the learned search embedding
reflects image similarity. Learning an embedding that discriminates
fine-grained variations in style is hard, due to the difficulty of defining and
labelling style. ALADIN takes a weakly supervised approach to learning a
representation for fine-grained style similarity of digital artworks,
leveraging BAM-FG, a novel large-scale dataset of user generated content
groupings gathered from the web. ALADIN sets a new state of the art accuracy
for style-based visual search over both coarse labelled style data (BAM) and
BAM-FG; a new 2.62 million image dataset of 310,000 fine-grained style
groupings also contributed by this work
- …