4,422 research outputs found
Learning Image-Specific Attributes by Hyperbolic Neighborhood Graph Propagation
As a kind of semantic representation of visual object descriptions,
attributes are widely used in various computer vision tasks. In most of
existing attribute-based research, class-specific attributes (CSA), which are
class-level annotations, are usually adopted due to its low annotation cost for
each class instead of each individual image. However, class-specific attributes
are usually noisy because of annotation errors and diversity of individual
images. Therefore, it is desirable to obtain image-specific attributes (ISA),
which are image-level annotations, from the original class-specific attributes.
In this paper, we propose to learn image-specific attributes by graph-based
attribute propagation. Considering the intrinsic property of hyperbolic
geometry that its distance expands exponentially, hyperbolic neighborhood graph
(HNG) is constructed to characterize the relationship between samples. Based on
HNG, we define neighborhood consistency for each sample to identify
inconsistent samples. Subsequently, inconsistent samples are refined based on
their neighbors in HNG. Extensive experiments on five benchmark datasets
demonstrate the significant superiority of the learned image-specific
attributes over the original class-specific attributes in the zero-shot object
classification task.Comment: Accepted for IJCAI 201
Positivity and vanishing theorems for ample vector bundles
In this paper, we study the Nakano-positivity and dual-Nakano-positivity of
certain adjoint vector bundles associated to ample vector bundles. As
applications, we get new vanishing theorems about ample vector bundles. For
example, we prove that if is an ample vector bundle over a compact K\"ahler
manifold , S^kE\ts \det E is both Nakano-positive and dual-Nakano-positive
for any . Moreover, H^{n,q}(X,S^kE\ts \det E)=H^{q,n}(X,S^kE\ts \det
E)=0 for any . In particular, if is a Griffiths-positive
vector bundle, the naturally induced Hermitian vector bundle (S^kE\ts \det E,
S^kh\ts \det h) is both Nakano-positive and dual-Nakano-positive for any
.Comment: 27 page
Crystal Field Effect Induced Topological Crystalline Insulators In Monolayer IV-VI Semiconductors
Two-dimensional (2D) topological crystalline insulators (TCIs) were recently
predicted in thin films of the SnTe class of IV-VI semiconductors, which can
host metallic edge states protected by mirror symmetry. As thickness decreases,
quantum confinement effect will increase and surpass the inverted gap below a
critical thickness, turning TCIs into normal insulators. Surprisingly, based on
first-principles calculations, here we demonstrate that (001) monolayers of
rocksalt IV-VI semiconductors XY (X=Ge, Sn, Pb and Y= S, Se, Te) are 2D TCIs
with the fundamental band gap as large as 260 meV in monolayer PbTe, providing
a materials platform for realizing two-dimensional Dirac fermion systems with
tunable band gap. This unexpected nontrivial topological phase stems from the
strong {\it crystal field effect} in the monolayer, which lifts the degeneracy
between and orbitals and leads to band inversion between cation
and anion orbitals. This crystal field effect induced
topological phase offers a new strategy to find and design other atomically
thin 2D topological materials.Comment: submitted in Jan. 2015 and published in Nano Let
Fast Online Clustering with Randomized Skeleton Sets
We present a new fast online clustering algorithm that reliably recovers
arbitrary-shaped data clusters in high throughout data streams. Unlike the
existing state-of-the-art online clustering methods based on k-means or
k-medoid, it does not make any restrictive generative assumptions. In addition,
in contrast to existing nonparametric clustering techniques such as DBScan or
DenStream, it gives provable theoretical guarantees. To achieve fast
clustering, we propose to represent each cluster by a skeleton set which is
updated continuously as new data is seen. A skeleton set consists of weighted
samples from the data where weights encode local densities. The size of each
skeleton set is adapted according to the cluster geometry. The proposed
technique automatically detects the number of clusters and is robust to
outliers. The algorithm works for the infinite data stream where more than one
pass over the data is not feasible. We provide theoretical guarantees on the
quality of the clustering and also demonstrate its advantage over the existing
state-of-the-art on several datasets
Shared quantum control via sharing operation on remote single qutrit
Two qubit operation sharing schemes [J. Phys. B 44 (2011) 165508] are
generalized to qutrit ones. Operations to be shared are classified into three
different classes in terms of different probabilities (i.e, 1/3, 2/3 and 1).
For the latter two classes, ten and three restricted sets of operations are
found out, respectively. Moreover, the two generalized schemes are amply
compared from four aspects, namely, quantum and classical resource consumption,
necessaryoperation complexity, success probability and efficiency. It is found
that the second scheme is overall more optimal than the first one as far as
three restricted sets of operations are concerned
Canonical Metrics on the Moduli Space of Riemann Surfaces I
We prove the equivalences of several classical complete metrics on the
Teichm\"uller and the moduli spaces of Riemann surfaces. We use as bridge two
new K\"ahler metrics, the Ricci metric and the perturbed Ricci metric and prove
that the perturbed Ricci metric is a complete K\"ahler metric with bounded
negative holomorphic sectional curvature and bounded bisectional and Ricci
curvature. As consequences we prove that these two new metrics are equivalent
to several famous classical metrics, which inlcude the Teichm\"uller metric,
therefore the Kabayashi metric, the K\"ahler-Einstein metric and the McMullen
metric. This also solves a conjecture of Yau in the early 80s.Comment: 42 page
Canonical Metrics on the Moduli Space of Riemann Surfaces II
In this paper we continue our study on the canonical metrics on the
Teichm\"uller and the moduli space of Riemman surfaces. We first prove the
equivalence of the Bergman metric and the Carath\'eodory metric to the
K\"ahler-Einstein metric, solving another old conjecture of Yau. We then prove
that the Ricci curvature of the perturbed Ricci metric has negative upper and
lower bounds, and it also has bounded geometry. Then we study in detail the
boundary behaviors of the K\"ahler-Einstein metric and prove that it has
bounded geometry, and all of the covariant derivatives of its curvature are
uniformly bounded on the Teichm\"uller space. As an application of our detailed
understanding of these metrics, we prove that the logarithmic cotangent bundle
of the moduli space is stable in the sense of Mumford.Comment: 40 page
Complementary Attributes: A New Clue to Zero-Shot Learning
Zero-shot learning (ZSL) aims to recognize unseen objects using disjoint seen
objects via sharing attributes. The generalization performance of ZSL is
governed by the attributes, which transfer semantic information from seen
classes to unseen classes. To take full advantage of the knowledge transferred
by attributes, in this paper, we introduce the notion of complementary
attributes (CA), as a supplement to the original attributes, to enhance the
semantic representation ability. Theoretical analyses demonstrate that
complementary attributes can improve the PAC-style generalization bound of
original ZSL model. Since the proposed CA focuses on enhancing the semantic
representation, CA can be easily applied to any existing attribute-based ZSL
methods, including the label-embedding strategy based ZSL (LEZSL) and the
probability-prediction strategy based ZSL (PPZSL). In PPZSL, there is a strong
assumption that all the attributes are independent of each other, which is
arguably unrealistic in practice. To solve this problem, a novel rank
aggregation framework is proposed to circumvent the assumption. Extensive
experiments on five ZSL benchmark datasets and the large-scale ImageNet dataset
demonstrate that the proposed complementary attributes and rank aggregation can
significantly and robustly improve existing ZSL methods and achieve the
state-of-the-art performance.Comment: Accepted by IEEE TRANSACTIONS ON CYBERNETIC
Cumulants of Net-Proton, Net-Kaon and Net-Charge Multiplicity Distributions in Au+Au Collisions at RHIC BES Energies from UrQMD Model
Fluctuations of conserved quantities are sensitive observables to probe the
signature of QCD phase transition and critical point in heavy-ion collisions.
With the UrQMD model, we have studied the centrality and energy dependence of
various order cumulants and cumulant ratios (up to fourth order) of
net-proton,net-charge and net-kaon multiplicity distributions in Au+Au
collisions at = 7.7, 11.5, 19.6, 27, 39, 62.4, 200 GeV. The
model results show that the production mechanism of the particles and
anti-particles have significant impacts on the cumulants of net-particles
multiplicity distributions and show strong energy dependence. We also made
comparisons between model calculations and experimental data measured in the
first phase of the beam energy scan (BES) program by the STAR experiment at
RHIC. The comparisons indicate that the baryon conservation effect strongly
suppress the cumulants of net-proton distributions at low energies and the
non-monotonic energy dependence for the net-proton {\KV} at the most central
Au+Au collisions measured by the STAR experiment can not be described by the
UrQMD model. Since there has no physics of QCD phase transition and QCD
critical point implemented in the UrQMD, the model results provide us baselines
and qualitative estimates about the non-critical background contributions to
the fluctuations observables in heavy-ion collisions.Comment: 9 pages, 10 figure
Human hexokinase: multiple mechanisms of G6P inhibition
Human hexokinase I catalyzes the first step in glycolysis, playing a key role in the energy metabolism of brain tissue. The chapters included in this thesis focus on structure-function relationships of hexokinase I. Glucose 6-phosphate (G6P), the reaction product, binds to hexokinase I with apparent negative cooperativity and inhibits catalysis (Chapter II). Both N- and C-terminal binding sites for G6P are functional, yet only one G6P molecule binds to hexokinase I.;A series of site-directed mutations were constructed in the base- and ribose-binding pocket of ATP in C-terminal half of hexokinase I G6P inhibition completely (Chapter III). The same mutations in the context of a truncated form of hexokinase I, which contains only the C-terminal half of the enzyme (mini-hexokinase), do not affect G6P inhibition. Obviously, the effects of the same mutations in full-length and mini-hexokinase I are different. On the basis of these results and structural information, we propose a model for allosteric G6P inhibition of hexokinase I. G6P binds to N-terminal half that reaches the active site of the C-terminal half. Furthermore, the results here suggest that the base- and ribose-binding pocket is the target of allosteric inhibition.;Chapter IV investigates the conformation of hexokinase I under different ligation states. The interface mutant engineered for the investigation is proved to be monomeric by small angel x-ray scattering and x-ray crystallography. The monomeric interface mutant and wild-type hexokinase I have essentially identical kinetic properties, thus evidently dimerization plays no role in hexokinase I function under conditions of in vitro. Small angle x-ray scattering data are consistent with the retention of a rod-like conformation under different ligation states, suggesting only subtle conformational changes in response to different ligands.;Chapter V reveals the ADP binding site in the C-terminal half of hexokinase I. Also, it suggests the location of allosteric interface between the N- and C-halves. Combining the structural information and kinetic results, the authors propose molecular mechanism of allosteric inhibition
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