10,023 research outputs found
A City-Scale ITS-G5 Network for Next-Generation Intelligent Transportation Systems: Design Insights and Challenges
As we move towards autonomous vehicles, a reliable Vehicle-to-Everything
(V2X) communication framework becomes of paramount importance. In this paper we
present the development and the performance evaluation of a real-world
vehicular networking testbed. Our testbed, deployed in the heart of the City of
Bristol, UK, is able to exchange sensor data in a V2X manner. We will describe
the testbed architecture and its operational modes. Then, we will provide some
insight pertaining the firmware operating on the network devices. The system
performance has been evaluated under a series of large-scale field trials,
which have proven how our solution represents a low-cost high-quality framework
for V2X communications. Our system managed to achieve high packet delivery
ratios under different scenarios (urban, rural, highway) and for different
locations around the city. We have also identified the instability of the
packet transmission rate while using single-core devices, and we present some
future directions that will address that.Comment: Accepted for publication to AdHoc-Now 201
Functional Electrical Stimulation mediated by Iterative Learning Control and 3D robotics reduces motor impairment in chronic stroke
Background: Novel stroke rehabilitation techniques that employ electrical stimulation (ES) and robotic technologies are effective in reducing upper limb impairments. ES is most effective when it is applied to support the patients’ voluntary effort; however, current systems fail to fully exploit this connection. This study builds on previous work using advanced ES controllers, and aims to investigate the feasibility of Stimulation Assistance through Iterative Learning (SAIL), a novel upper limb stroke rehabilitation system which utilises robotic support, ES, and voluntary effort. Methods: Five hemiparetic, chronic stroke participants with impaired upper limb function attended 18, 1 hour intervention sessions. Participants completed virtual reality tracking tasks whereby they moved their impaired arm to follow a slowly moving sphere along a specified trajectory. To do this, the participants’ arm was supported by a robot. ES, mediated by advanced iterative learning control (ILC) algorithms, was applied to the triceps and anterior deltoid muscles. Each movement was repeated 6 times and ILC adjusted the amount of stimulation applied on each trial to improve accuracy and maximise voluntary effort. Participants completed clinical assessments (Fugl-Meyer, Action Research Arm Test) at baseline and post-intervention, as well as unassisted tracking tasks at the beginning and end of each intervention session. Data were analysed using t-tests and linear regression. Results: From baseline to post-intervention, Fugl-Meyer scores improved, assisted and unassisted tracking performance improved, and the amount of ES required to assist tracking reduced. Conclusions: The concept of minimising support from ES using ILC algorithms was demonstrated. The positive results are promising with respect to reducing upper limb impairments following stroke, however, a larger study is required to confirm this
Volterra-type inner derivations on Hardy spaces
A classical result of Calkin [Ann. of Math. (2) 42 (1941), pp. 839-873] says
that an inner derivation maps the algebra of bounded
operators on a Hilbert space into the ideal of compact operators if and only if
is a compact perturbation of the multiplication by a scalar. In general, an
analogous statement fails for operators on Banach spaces. To complement
Calkin's result, we characterize Volterra-type inner derivations on Hardy
spaces using generalized area operators and compact intertwining relations for
Volterra and composition operators. Further, we characterize the compact
intertwining relations for multiplication and composition operators between
Hardy and Bergman spaces
Environment Sensing Considering the Occlusion Effect: A Multi-View Approach
In this paper, we consider the problem of sensing the environment within a wireless cellular framework. Specifically, multiple user equipments (UEs) send sounding signals to one or multiple base stations (BSs) and then a centralized processor retrieves the environmental information from all the channel information obtained at the BS(s). Taking into account the occlusion effect that is common in the wireless context, we make full use of the different views of the environment from different users and/or BS(s), and propose an effective sensing algorithm called GAMP-MVSVR (generalized-approximate-message-passing-based multi-view sparse vector reconstruction). In the proposed algorithm, a multi-layer factor graph is constructed to iteratively estimate the scattering coefficients of the cloud points and their occlusion relationship. In each iteration, the occlusion relationship between the cloud points of the sparse environment is recalculated according to a simple occlusion detection rule, and in turn, used to estimate the scattering coefficients of the cloud points. Our proposed algorithm can achieve improved sensing performance with multi-BS collaboration in addition to the multi-views from the UEs. The simulation results verify its convergence and effectiveness
On Propagation Characteristics of Reconfigurable Surface Wave Platform: Simulation and Experimental Verification
Reconfigurable intelligent surface (RIS) as a smart reflector is
revolutionizing research for next-generation wireless communications.
Complementing this is a concept of using RIS as an efficient propagation medium
for potentially superior path loss characteristics. Motivated by a recent
porous surface architecture that facilitates reconfigurable pathways with
cavities filled with fluid metal, this paper studies the propagation
characteristics of different pathway configurations in different lossy
materials on the reconfigurable surface wave platform by using a commercial
full electromagnetic simulation software and S-parameters experiments. This
paper also looks into the best scheme to switch between a straight pathway and
a -bend and attempts to quantify the additional path loss when making
a turn. Our experimental results verify the simulation results, showing the
effectiveness of the proposed reconfigurable surface wave platform for a
wide-band, low path loss and highly programmable communications.Comment: Submitted to IEEE TRANSACTIONS ON ANTENNAS AND PROPAGATION, 202
Coexistence of superconductivity and magnetism in K0.8Fe2Se1.4S0.4
High-quality single crystals of K0.8Fe2Se1.4S0.4 are successfully synthesized
by self-flux method with the superconducting transition temperatures Tconset =
32.8 K and Tczero = 31.2 K. In contrast to external pressure effect on
superconductivity, the substitution of S for Se does not suppress Tc, which
suggests that chemical doping may mainly modulate the anion height from
Fe-layer rather than compressing interlayer distance. The investigation of the
micromagnetism by electron spin resonance shows clear evidence for strong spin
fluctuation at temperatures above Tc. Accompanied by the superconducting
feature spectra, a novel resonance signal develops gradually upon cooling below
Tc, indicating the coexistence of superconductivity and magnetism in
K0.8Fe2Se1.4S0.4 crystal
- …