3,773 research outputs found
Reconstructing 3D Human Pose from RGB-D Data with Occlusions
We propose a new method to reconstruct the 3D human body from RGB-D images
with occlusions. The foremost challenge is the incompleteness of the RGB-D data
due to occlusions between the body and the environment, leading to implausible
reconstructions that suffer from severe human-scene penetration. To reconstruct
a semantically and physically plausible human body, we propose to reduce the
solution space based on scene information and prior knowledge. Our key idea is
to constrain the solution space of the human body by considering the occluded
body parts and visible body parts separately: modeling all plausible poses
where the occluded body parts do not penetrate the scene, and constraining the
visible body parts using depth data. Specifically, the first component is
realized by a neural network that estimates the candidate region named the
"free zone", a region carved out of the open space within which it is safe to
search for poses of the invisible body parts without concern for penetration.
The second component constrains the visible body parts using the "truncated
shadow volume" of the scanned body point cloud. Furthermore, we propose to use
a volume matching strategy, which yields better performance than surface
matching, to match the human body with the confined region. We conducted
experiments on the PROX dataset, and the results demonstrate that our method
produces more accurate and plausible results compared with other methods
End-to-end Structure-Aware Convolutional Networks for Knowledge Base Completion
Knowledge graph embedding has been an active research topic for knowledge
base completion, with progressive improvement from the initial TransE, TransH,
DistMult et al to the current state-of-the-art ConvE. ConvE uses 2D convolution
over embeddings and multiple layers of nonlinear features to model knowledge
graphs. The model can be efficiently trained and scalable to large knowledge
graphs. However, there is no structure enforcement in the embedding space of
ConvE. The recent graph convolutional network (GCN) provides another way of
learning graph node embedding by successfully utilizing graph connectivity
structure. In this work, we propose a novel end-to-end Structure-Aware
Convolutional Network (SACN) that takes the benefit of GCN and ConvE together.
SACN consists of an encoder of a weighted graph convolutional network (WGCN),
and a decoder of a convolutional network called Conv-TransE. WGCN utilizes
knowledge graph node structure, node attributes and edge relation types. It has
learnable weights that adapt the amount of information from neighbors used in
local aggregation, leading to more accurate embeddings of graph nodes. Node
attributes in the graph are represented as additional nodes in the WGCN. The
decoder Conv-TransE enables the state-of-the-art ConvE to be translational
between entities and relations while keeps the same link prediction performance
as ConvE. We demonstrate the effectiveness of the proposed SACN on standard
FB15k-237 and WN18RR datasets, and it gives about 10% relative improvement over
the state-of-the-art ConvE in terms of HITS@1, HITS@3 and [email protected]: The Thirty-Third AAAI Conference on Artificial Intelligence (AAAI
2019
Mean field stochastic control under sublinear expectation
Our work is devoted to the study of Pontryagin's stochastic maximum principle
for a mean-field optimal control problem under Peng's -expectation. The
dynamics of the controlled state process is given by a stochastic differential
equation driven by a -Brownian motion, whose coefficients depend not only on
the control, the controlled state process but also on its law under the
-expectation. Also the associated cost functional is of mean-field type.
Under the assumption of a convex control state space we study the stochastic
maximum principle, which gives a necessary optimality condition for control
processes. Under additional convexity assumptions on the Hamiltonian it is
shown that this necessary condition is also a sufficient one. The main
difficulty which we have to overcome in our work consists in the
differentiation of the -expectation of parameterized random variables. As
particularly delicate it turns out to handle with the -expectation of a
function of the controlled state process inside the running cost of the cost
function. For this we have to study a measurable selection theorem for
set-valued functions whose values are subsets of the representing set of
probability measures for the -expectation.Comment: 34 page
Harnessing The Collective Wisdom: Fusion Learning Using Decision Sequences From Diverse Sources
Learning from the collective wisdom of crowds enhances the transparency of
scientific findings by incorporating diverse perspectives into the
decision-making process. Synthesizing such collective wisdom is related to the
statistical notion of fusion learning from multiple data sources or studies.
However, fusing inferences from diverse sources is challenging since
cross-source heterogeneity and potential data-sharing complicate statistical
inference. Moreover, studies may rely on disparate designs, employ widely
different modeling techniques for inferences, and prevailing data privacy norms
may forbid sharing even summary statistics across the studies for an overall
analysis. In this paper, we propose an Integrative Ranking and Thresholding
(IRT) framework for fusion learning in multiple testing. IRT operates under the
setting where from each study a triplet is available: the vector of binary
accept-reject decisions on the tested hypotheses, the study-specific False
Discovery Rate (FDR) level and the hypotheses tested by the study. Under this
setting, IRT constructs an aggregated, nonparametric, and discriminatory
measure of evidence against each null hypotheses, which facilitates ranking the
hypotheses in the order of their likelihood of being rejected. We show that IRT
guarantees an overall FDR control under arbitrary dependence between the
evidence measures as long as the studies control their respective FDR at the
desired levels. Furthermore, IRT synthesizes inferences from diverse studies
irrespective of the underlying multiple testing algorithms employed by them.
While the proofs of our theoretical statements are elementary, IRT is extremely
flexible, and a comprehensive numerical study demonstrates that it is a
powerful framework for pooling inferences.Comment: 29 pages and 10 figures. Under review at a journa
Thin film superfluid optomechanics
Excitations in superfluid helium represent attractive mechanical degrees of
freedom for cavity optomechanics schemes. Here we numerically and analytically
investigate the properties of optomechanical resonators formed by thin films of
superfluid He covering micrometer-scale whispering gallery mode cavities.
We predict that through proper optimization of the interaction between film and
optical field, large optomechanical coupling rates kHz
and single photon cooperativities are achievable. Our analytical model
reveals the unconventional behaviour of these thin films, such as thicker and
heavier films exhibiting smaller effective mass and larger zero point motion.
The optomechanical system outlined here provides access to unusual regimes such
as and opens the prospect of laser cooling a liquid into its
quantum ground state.Comment: 18 pages, 6 figure
Recommended from our members
Hypoxic Preconditioning Enhances Survival and Proangiogenic Capacity of Human First Trimester Chorionic Villus-Derived Mesenchymal Stem Cells for Fetal Tissue Engineering.
Prenatal stem cell-based regenerative therapies have progressed substantially and have been demonstrated as effective treatment options for fetal diseases that were previously deemed untreatable. Due to immunoregulatory properties, self-renewal capacity, and multilineage potential, autologous human placental chorionic villus-derived mesenchymal stromal cells (CV-MSCs) are an attractive cell source for fetal regenerative therapies. However, as a general issue for MSC transplantation, the poor survival and engraftment is a major challenge of the application of MSCs. Particularly for the fetal transplantation of CV-MSCs in the naturally hypoxic fetal environment, improving the survival and engraftment of CV-MSCs is critically important. Hypoxic preconditioning (HP) is an effective priming approach to protect stem cells from ischemic damage. In this study, we developed an optimal HP protocol to enhance the survival and proangiogenic capacity of CV-MSCs for improving clinical outcomes in fetal applications. Total cell number, DNA quantification, nuclear area test, and cell viability test showed HP significantly protected CV-MSCs from ischemic damage. Flow cytometry analysis confirmed HP did not alter the immunophenotype of CV-MSCs. Caspase-3, MTS, and Western blot analysis showed HP significantly reduced the apoptosis of CV-MSCs under ischemic stimulus via the activation of the AKT signaling pathway that was related to cell survival. ELISA results showed HP significantly enhanced the secretion of vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) by CV-MSCs under an ischemic stimulus. We also found that the environmental nutrition level was critical for the release of brain-derived neurotrophic factor (BDNF). The angiogenesis assay results showed HP-primed CV-MSCs could significantly enhance endothelial cell (EC) proliferation, migration, and tube formation. Consequently, HP is a promising strategy to increase the tolerance of CV-MSCs to ischemia and improve their therapeutic efficacy in fetal clinical applications
Microphotonic Forces From Superfluid Flow
In cavity optomechanics, radiation pressure and photothermal forces are
widely utilized to cool and control micromechanical motion, with applications
ranging from precision sensing and quantum information to fundamental science.
Here, we realize an alternative approach to optical forcing based on superfluid
flow and evaporation in response to optical heating. We demonstrate optical
forcing of the motion of a cryogenic microtoroidal resonator at a level of 1.46
nN, roughly one order of magnitude larger than the radiation pressure force. We
use this force to feedback cool the motion of a microtoroid mechanical mode to
137 mK. The photoconvective forces demonstrated here provide a new tool for
high bandwidth control of mechanical motion in cryogenic conditions, and have
the potential to allow efficient transfer of electromagnetic energy to motional
kinetic energy.Comment: 5 pages, 6 figure
Modelling of vorticity, sound and their interaction in two-dimensional superfluids
Vorticity in two-dimensional superfluids is subject to intense research
efforts due to its role in quantum turbulence, dissipation and the BKT phase
transition. Interaction of sound and vortices is of broad importance in
Bose-Einstein condensates and superfluid helium [1-4]. However, both the
modelling of the vortex flow field and of its interaction with sound are
complicated hydrodynamic problems, with analytic solutions only available in
special cases. In this work, we develop methods to compute both the vortex and
sound flow fields in an arbitrary two-dimensional domain. Further, we analyse
the dispersive interaction of vortices with sound modes in a two-dimensional
superfluid and develop a model that quantifies this interaction for any vortex
distribution on any two-dimensional bounded domain, possibly non-simply
connected, exploiting analogies with fluid dynamics of an ideal gas and
electrostatics. As an example application we use this technique to propose an
experiment that should be able to unambiguously detect single circulation
quanta in a helium thin film.Comment: 23 pages, 8 figure
- …