64 research outputs found
Stability analysis of token-based wireless networked control systems under deception attacks
Currently, cyber-security has attracted a lot of attention, in particular in wireless industrial control networks (WICNs). In this paper, the stability of wireless networked control systems (WNCSs) under deception, attacks is studied with a token-based protocol applied to the data link layer (DLL) of WICNS. Since deception attacks cause the stability problem of WNCSs by changing the data transmitted over a wireless network, it is important to detect deception attacks, discard the injected false data and compensate for the missing data (i.e., the discarded original data with the injected false data). The main contributions of this paper are: 1) With respect to the character of the token-based protocol, a switched system model is developed. Different from the traditional switched system where the number of subsystems is fixed, in our new model this number will be changed under deception attacks. 2) For this model, a new Kalman filter (KF) is developed for the purpose of attack detection and the missing data reconstruction. 3) For the given linear feedback WNCSs, when the noise level is below a threshold derived in this paper, the maximum allowable duration of deception attacks is obtained to maintain the exponential stability of the system. Finally, a numerical example based on a linearized model of an inverted pendulum is provided to demonstrate the proposed design
Passive Non-line-of-sight Imaging for Moving Targets with an Event Camera
Non-line-of-sight (NLOS) imaging is an emerging technique for detecting
objects behind obstacles or around corners. Recent studies on passive NLOS
mainly focus on steady-state measurement and reconstruction methods, which show
limitations in recognition of moving targets. To the best of our knowledge, we
propose a novel event-based passive NLOS imaging method. We acquire
asynchronous event-based data which contains detailed dynamic information of
the NLOS target, and efficiently ease the degradation of speckle caused by
movement. Besides, we create the first event-based NLOS imaging dataset,
NLOS-ES, and the event-based feature is extracted by time-surface
representation. We compare the reconstructions through event-based data with
frame-based data. The event-based method performs well on PSNR and LPIPS, which
is 20% and 10% better than frame-based method, while the data volume takes only
2% of traditional method
New insight into the electronic shell of Au-38(SR)(24): a superatomic molecule
National Key Basic Research Program of China [2011CB921404]; National Natural Science Foundation of China [20903001, 21121003, 21273008, 21233007, 91021004]; CAS [XDB01020300]; 211 Project; outstanding youth foundation of Anhui UniversityBased on the recently proposed super valence bond model, in which superatoms can compose superatomic molecules by sharing valence pairs and nuclei for shell closure, the 23c-14e bi-icosahedral Au-23((+9)) core of Au-38(SR)(24) is proved to be a superatomic molecule. Molecular orbital analysis reveals that the Au-23((+9)) core is an exact analogue of the F-2 molecule in electronic configuration. Chemical bonding analysis by the adaptive natural density partitioning method confirms the superatomic molecule bonding framework of Au-38(24)(SR) in a straightforward manner
Search for light dark matter from atmosphere in PandaX-4T
We report a search for light dark matter produced through the cascading decay
of mesons, which are created as a result of inelastic collisions between
cosmic rays and Earth's atmosphere. We introduce a new and general framework,
publicly accessible, designed to address boosted dark matter specifically, with
which a full and dedicated simulation including both elastic and quasi-elastic
processes of Earth attenuation effect on the dark matter particles arriving at
the detector is performed. In the PandaX-4T commissioning data of 0.63
tonneyear exposure, no significant excess over background is observed.
The first constraints on the interaction between light dark matter generated in
the atmosphere and nucleus through a light scalar mediator are obtained. The
lowest excluded cross-section is set at for
dark matter mass of MeV and mediator mass of 300 MeV. The
lowest upper limit of to dark matter decay branching ratio is
A Search for Light Fermionic Dark Matter Absorption on Electrons in PandaX-4T
We report a search on a sub-MeV fermionic dark matter absorbed by electrons
with an outgoing active neutrino using the 0.63 tonne-year exposure collected
by PandaX-4T liquid xenon experiment. No significant signals are observed over
the expected background. The data are interpreted into limits to the effective
couplings between such dark matter and electrons. For axial-vector or vector
interactions, our sensitivity is competitive in comparison to existing
astrophysical bounds on the decay of such dark matter into photon final states.
In particular, we present the first direct detection limits for an axial-vector
(vector) interaction which are the strongest in the mass range from 25 to 45
(35 to 50) keV/c
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