9,662 research outputs found
A Visual Representation-guided Framework with Global Affinity for Weakly Supervised Salient Object Detection
Fully supervised salient object detection (SOD) methods have made
considerable progress in performance, yet these models rely heavily on
expensive pixel-wise labels. Recently, to achieve a trade-off between labeling
burden and performance, scribble-based SOD methods have attracted increasing
attention. Previous scribble-based models directly implement the SOD task only
based on SOD training data with limited information, it is extremely difficult
for them to understand the image and further achieve a superior SOD task. In
this paper, we propose a simple yet effective framework guided by general
visual representations with rich contextual semantic knowledge for
scribble-based SOD. These general visual representations are generated by
self-supervised learning based on large-scale unlabeled datasets. Our framework
consists of a task-related encoder, a general visual module, and an information
integration module to efficiently combine the general visual representations
with task-related features to perform the SOD task based on understanding the
contextual connections of images. Meanwhile, we propose a novel global semantic
affinity loss to guide the model to perceive the global structure of the
salient objects. Experimental results on five public benchmark datasets
demonstrate that our method, which only utilizes scribble annotations without
introducing any extra label, outperforms the state-of-the-art weakly supervised
SOD methods. Specifically, it outperforms the previous best scribble-based
method on all datasets with an average gain of 5.5% for max f-measure, 5.8% for
mean f-measure, 24% for MAE, and 3.1% for E-measure. Moreover, our method
achieves comparable or even superior performance to the state-of-the-art fully
supervised models
Learning to Assist Different Wearers in Multitasks: Efficient and Individualized Human-In-the-Loop Adaption Framework for Exoskeleton Robots
One of the typical purposes of using lower-limb exoskeleton robots is to
provide assistance to the wearer by supporting their weight and augmenting
their physical capabilities according to a given task and human motion
intentions. The generalizability of robots across different wearers in multiple
tasks is important to ensure that the robot can provide correct and effective
assistance in actual implementation. However, most lower-limb exoskeleton
robots exhibit only limited generalizability. Therefore, this paper proposes a
human-in-the-loop learning and adaptation framework for exoskeleton robots to
improve their performance in various tasks and for different wearers. To suit
different wearers, an individualized walking trajectory is generated online
using dynamic movement primitives and Bayes optimization. To accommodate
various tasks, a task translator is constructed using a neural network to
generalize a trajectory to more complex scenarios. These generalization
techniques are integrated into a unified variable impedance model, which
regulates the exoskeleton to provide assistance while ensuring safety. In
addition, an anomaly detection network is developed to quantitatively evaluate
the wearer's comfort, which is considered in the trajectory learning procedure
and contributes to the relaxation of conflicts in impedance control. The
proposed framework is easy to implement, because it requires proprioceptive
sensors only to perform and deploy data-efficient learning schemes. This makes
the exoskeleton practical for deployment in complex scenarios, accommodating
different walking patterns, habits, tasks, and conflicts. Experiments and
comparative studies on a lower-limb exoskeleton robot are performed to
demonstrate the effectiveness of the proposed framework.Comment: 16 pages journal articl
Kerr-Sen Black Hole as Accelerator for Spinning Particles
It has been proved that arbitrarily high-energy collision between two
particles can occur near the horizon of an extremal Kerr black hole as long as
the energy and angular momentum of one particle satisfies a critical
relation, which is called the BSW mechanism. Previous researchers mainly
concentrate on geodesic motion of particles. In this paper, we will take
spinning particle which won't move along a timelike geodesic into our
consideration, hence, another parameter describing the particle's spin
angular momentum was introduced. By employing the Mathisson-Papapetrou-Dixon
equation describing the movement of spinning particle, we will explore whether
a Kerr-Sen black hole which is slightly different from Kerr black hole can be
used to accelerate a spinning particle to arbitrarily high energy. We found
that when one of the two colliding particles satisfies a critical relation
between the energy and the total angular momentum , or has a critical
spinning angular momentum , a divergence of the center-of-mass energy
will be obtained.Comment: Latex,17 pages,1 figure,minor revision,accepted by PR
Observation of coherent oscillation in single-passage Landau-Zener transitions
Landau-Zener transition (LZT) has been explored in a variety of physical
systems for coherent population transfer between different quantum states. In
recent years, there have been various proposals for applying LZT to quantum
information processing because when compared to the methods using ac pulse for
coherent population transfer, protocols based on LZT are less sensitive to
timing errors. However, the effect of finite range of qubit energy available to
LZT based state control operations has not been thoroughly examined. In this
work, we show that using the well-known Landau-Zener formula in the vicinity of
an avoided energy-level crossing will cause considerable errors due to coherent
oscillation of the transition probability in a single-passage LZT experiment.
The data agree well with the numerical simulations which take the transient
dynamics of LZT into account. These results not only provide a closer view on
the issue of finite-time LZT but also shed light on its effects on the quantum
state manipulation.Comment: 10 pages,5 figure
- …