493 research outputs found
Pose Uncertainty Aware Movement Synchrony Estimation via Spatial-Temporal Graph Transformer
Movement synchrony reflects the coordination of body movements between
interacting dyads. The estimation of movement synchrony has been automated by
powerful deep learning models such as transformer networks. However, instead of
designing a specialized network for movement synchrony estimation, previous
transformer-based works broadly adopted architectures from other tasks such as
human activity recognition. Therefore, this paper proposed a skeleton-based
graph transformer for movement synchrony estimation. The proposed model applied
ST-GCN, a spatial-temporal graph convolutional neural network for skeleton
feature extraction, followed by a spatial transformer for spatial feature
generation. The spatial transformer is guided by a uniquely designed joint
position embedding shared between the same joints of interacting individuals.
Besides, we incorporated a temporal similarity matrix in temporal attention
computation considering the periodic intrinsic of body movements. In addition,
the confidence score associated with each joint reflects the uncertainty of a
pose, while previous works on movement synchrony estimation have not
sufficiently emphasized this point. Since transformer networks demand a
significant amount of data to train, we constructed a dataset for movement
synchrony estimation using Human3.6M, a benchmark dataset for human activity
recognition, and pretrained our model on it using contrastive learning. We
further applied knowledge distillation to alleviate information loss introduced
by pose detector failure in a privacy-preserving way. We compared our method
with representative approaches on PT13, a dataset collected from autism therapy
interventions. Our method achieved an overall accuracy of 88.98% and surpassed
its counterparts by a wide margin while maintaining data privacy.Comment: Accepted by 24th ACM International Conference on Multimodal
Interaction (ICMI'22). 17 pages, 2 figure
Dyadic Movement Synchrony Estimation Under Privacy-preserving Conditions
Movement synchrony refers to the dynamic temporal connection between the
motions of interacting people. The applications of movement synchrony are wide
and broad. For example, as a measure of coordination between teammates,
synchrony scores are often reported in sports. The autism community also
identifies movement synchrony as a key indicator of children's social and
developmental achievements. In general, raw video recordings are often used for
movement synchrony estimation, with the drawback that they may reveal people's
identities. Furthermore, such privacy concern also hinders data sharing, one
major roadblock to a fair comparison between different approaches in autism
research. To address the issue, this paper proposes an ensemble method for
movement synchrony estimation, one of the first deep-learning-based methods for
automatic movement synchrony assessment under privacy-preserving conditions.
Our method relies entirely on publicly shareable, identity-agnostic secondary
data, such as skeleton data and optical flow. We validate our method on two
datasets: (1) PT13 dataset collected from autism therapy interventions and (2)
TASD-2 dataset collected from synchronized diving competitions. In this
context, our method outperforms its counterpart approaches, both deep neural
networks and alternatives.Comment: IEEE ICPR 2022. 8 pages, 3 figure
Floquet Chern Insulators of Light
Achieving topologically-protected robust transport in optical systems has
recently been of great interest. Most topological photonic structures can be
understood by solving the eigenvalue problem of Maxwell's equations for a
static linear system. Here, we extend topological phases into dynamically
driven nonlinear systems and achieve a Floquet Chern insulator of light in
nonlinear photonic crystals (PhCs). Specifically, we start by presenting the
Floquet eigenvalue problem in driven two-dimensional PhCs and show it is
necessarily non-Hermitian. We then define topological invariants associated
with Floquet bands using non-Hermitian topological band theory, and show that
topological band gaps with non-zero Chern number can be opened by breaking
time-reversal symmetry through the driving field. Furthermore, we show that
topological phase transitions between Floquet Chern insulators and normal
insulators occur at synthetic Weyl points in a three-dimensional parameter
space consisting of two momenta and the driving frequency. Finally, we
numerically demonstrate the existence of chiral edge states at the interfaces
between a Floquet Chern insulator and normal insulators, where the transport is
non-reciprocal and uni-directional. Our work paves the way to further exploring
topological phases in driven nonlinear optical systems and their optoelectronic
applications, and our method of inducing Floquet topological phases is also
applicable to other wave systems, such as phonons, excitons, and polaritons
Birth of strange nonchaotic attractors in a piecewise linear oscillator
ACKNOWLEDGMENTS We sincerely thank the people who gave valuable comments. This paper was supported by the National Natural Science Foundation of China (NNSFC) (No. 12172306) and the Innovation Fund Project of Colleges and Universities in Gansu Province (No. 2021A-040).Peer reviewedPostprin
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