192 research outputs found
Deep-Reinforcement Learning Multiple Access for Heterogeneous Wireless Networks
This paper investigates the use of deep reinforcement learning (DRL) in a MAC
protocol for heterogeneous wireless networking referred to as
Deep-reinforcement Learning Multiple Access (DLMA). The thrust of this work is
partially inspired by the vision of DARPA SC2, a 3-year competition whereby
competitors are to come up with a clean-slate design that "best share spectrum
with any network(s), in any environment, without prior knowledge, leveraging on
machine-learning technique". Specifically, this paper considers the problem of
sharing time slots among a multiple of time-slotted networks that adopt
different MAC protocols. One of the MAC protocols is DLMA. The other two are
TDMA and ALOHA. The nodes operating DLMA do not know that the other two MAC
protocols are TDMA and ALOHA. Yet, by a series of observations of the
environment, its own actions, and the resulting rewards, a DLMA node can learn
an optimal MAC strategy to coexist harmoniously with the TDMA and ALOHA nodes
according to a specified objective (e.g., the objective could be the sum
throughput of all networks, or a general alpha-fairness objective)
Optimisation and Management of Energy Generated by a Multifunctional MFC-Integrated Composite Chassis for Rail Vehicles
With the advancing trend towards lighter and faster rail transport, there is an increasing interest in integrating composite and advanced multifunctional materials in order to infuse smart sensing and monitoring, energy harvesting and wireless capabilities within the otherwise purely mechanical rail structures and the infrastructure. This paper presents a holistic multiphysics numerical study, across both mechanical and electrical domains, that describes an innovative technique of harvesting energy from a piezoelectric micro fiber composites (MFC) built-in composite rail chassis structure. Representative environmental vibration data measured from a rail cabin have been critically leveraged here to help predict the actual vibratory and power output behaviour under service. Time domain mean stress distribution data from the Finite Element simulation were used to predict the raw AC voltage output of the MFCs. Conditioned power output was then calculated using circuit simulation of several state-of-the-art power conditioning circuits. A peak instantaneous rectified power of 181.9 mW was obtained when eight-stage Synchronised Switch Harvesting Capacitors (SSHC) from eight embedded MFCs were located. The results showed that the harvested energy could be sufficient to sustain a self-powered structural health monitoring system with wireless communication capabilities. This study serves as a theoretical foundation of scavenging for vibrational power from the ambient state in a rail environment as well as to pointing to design principles to develop regenerative and power neutral smart vehicles
Self-supervised Heterogeneous Graph Variational Autoencoders
Heterogeneous Information Networks (HINs), which consist of various types of
nodes and edges, have recently demonstrated excellent performance in graph
mining. However, most existing heterogeneous graph neural networks (HGNNs)
ignore the problems of missing attributes, inaccurate attributes and scarce
labels for nodes, which limits their expressiveness. In this paper, we propose
a generative self-supervised model SHAVA to address these issues
simultaneously. Specifically, SHAVA first initializes all the nodes in the
graph with a low-dimensional representation matrix. After that, based on the
variational graph autoencoder framework, SHAVA learns both node-level and
attribute-level embeddings in the encoder, which can provide fine-grained
semantic information to construct node attributes. In the decoder, SHAVA
reconstructs both links and attributes. Instead of directly reconstructing raw
features for attributed nodes, SHAVA generates the initial low-dimensional
representation matrix for all the nodes, based on which raw features of
attributed nodes are further reconstructed to leverage accurate attributes. In
this way, SHAVA can not only complete informative features for non-attributed
nodes, but rectify inaccurate ones for attributed nodes. Finally, we conduct
extensive experiments to show the superiority of SHAVA in tackling HINs with
missing and inaccurate attributes
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