Summary
This article presents a two‐layered framework to investigate the output synchronization problem in nonhomogeneous agent systems in the presence of periodic energy‐limited denial‐of‐service ...(DoS) attacks with an event‐triggered control strategy. Under the developed framework, the proposed controller for different agents is composed of a dynamic compensator and a regulator, where the dynamic compensator on the first layer can copy the dynamics of the leader node. DoS attacks with a periodic (partially known) attack strategy are based on a time sequence and interrupt the data exchange over a shard network consisting of the leader node and dynamic compensators in the first layer. An event‐triggered control protocol is proposed to reduce the update frequency of the controller, and it also ensures that the output of every dynamic compensator can track the output of the leader node without occurring “Zeno phenomenon.” Based on the output regulator theory, the regulator for every agent can guarantee that all nonhomogeneous agents can converge to the trajectory of every dynamic compensator in the bottom layer. Finally, a simulation example is demonstrated to verify the new design method developed.
For decreasing communication load and overcoming network constrains, such as the limited bandwidth and data loss in multi-agent networks, this paper integrates the two control strategies to ...investigate the bounded consensus problem of multi-agent systems (MASs) with external disturbance on the basis of an undirected graph, namely, the quantized control and the event-triggered control. In the existence of the external disturbance, two types of the high-gain control laws with the uniform quantized relative state measurements for the bounded consensus problem of MASs are first discussed, respectively. Then, in order to save the limited network resources in a multi-agent network, the event-triggered quantized communication protocols are designed based on the first case to obtain the bounded consensus in multi-agent systems. Moreover, it is shown that "Zeno behavior" phenomenon can be excluded under the two event-triggered quantized control mechanisms, and the boundness of the relative state error can be adjusted by selecting the different parameters. Finally, two examples are shown to validate the feasibility and efficiency of our theoretical analysis.
In this article, a distributed observer- and event-based practical consensus control for networked systems subject to adaptive nonlinear couplings is investigated. Considering that the node's state ...is not always measurable and the finite communication bandwidth exists in engineering systems, two distributed adaptive event-triggered control protocols subject to nonlinear couplings are proposed under observer-based dynamic output feedback. Then, distributed dynamic event-triggered control policies corresponding to two abovementioned adaptive controllers are proposed, respectively. The proposed nonlinear coupled event-triggered control schemes not only overcome continuous communication among nodes, but also relax the requirement of relying on global information for achieving a distributed practical consensus. Finally, the theoretical analysis is verified through a team of practical networked ground vehicles implemented through MATLAB/Simulink and robot operating systems environment.
Core–shell or striped heteroatomic lanthanide metal–organic framework hierarchical single crystals were obtained by liquid‐phase anisotropic epitaxial growth, maintaining identical periodic ...organization while simultaneously exhibiting spatially segregated structure. Different types of domain and orientation‐controlled multicolor photophysical models are presented, which show either visually distinguishable or visible/near infrared (NIR) emissive colors. This provides a new bottom‐up strategy toward the design of hierarchical molecular systems, offering high‐throughput and multiplexed luminescence color tunability and readability. The unique capability of combining spectroscopic coding with 3D (three‐dimensional) microscale spatial coding is established, providing potential applications in anti‐counterfeiting, color barcoding, and other types of integrated and miniaturized optoelectronic materials and devices.
A colorful turn: Core–shell (see picture, left) or striped (right) heteroatomic lanthanide metal–organic framework hierarchical single crystals are assembled from solution‐mediated epitaxial growth. By manipulation of the domain and orientation, tunable multicolor to white light emissions can be achieved. Multiplexed and high‐throughput capabilities are provided through the combination of spectroscopy with 3D‐space operation.
We report the results of our systematic survey for Galactic 6.7 GHz Class II CH3OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio ...Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky Wide-field Infrared Survey Explorer (WISE) point-source catalog. We discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e., ) in a previous paper (Yang et al. 2017). Here, we present the results from the survey of those at low Galactic latitudes, i.e., . Of 1875 selected WISE point sources, 291 positions that were actually associated with 224 sources that were detected with CH3OH maser emission. Among them, 32 are newly detected. A majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224 = 93.3%) are quite close to the Galactic Plane ( ) and lie on the inner spiral arms with positive local standard of rest velocities. The detection rate and the color-color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalog of 1085 sources with 6.7 GHz CH3OH maser emission in our Galaxy.
In this paper, the problem of distributed event-triggered pinning control for practical consensus of multiagent systems (MASs) with quantized communication based on a directed graph is investigated. ...The pinning control for practical consensus of MASs with uniform quantizer is first discussed. Then, in order to decrease communication load of interagent, the event-triggered quantized communication protocol is designed. The nonsmooth analysis and Gronwall's inequality approach is used to guarantee the existence of a solution to the resulting closed-loop system. It is shown that practical consensus is reachable through the event-triggered control and converges to a consensus set. Moreover, "Zeno phenomenon" can be excluded. Finally, an example is given to validate the feasibility and efficiency of the proposed new design method.
Purpose
To develop a deep learning‐based method for knee menisci segmentation in 3D ultrashort echo time (UTE) cones MR imaging, and to automatically determine MR relaxation times, namely the T1, ...T1ρ, and T2∗ parameters, which can be used to assess knee osteoarthritis (OA).
Methods
Whole knee joint imaging was performed using 3D UTE cones sequences to collect data from 61 human subjects. Regions of interest (ROIs) were outlined by 2 experienced radiologists based on subtracted T1ρ‐weighted MR images. Transfer learning was applied to develop 2D attention U‐Net convolutional neural networks for the menisci segmentation based on each radiologist's ROIs separately. Dice scores were calculated to assess segmentation performance. Next, the T1, T1ρ, T2∗ relaxations, and ROI areas were determined for the manual and automatic segmentations, then compared.
Results
The models developed using ROIs provided by 2 radiologists achieved high Dice scores of 0.860 and 0.833, while the radiologists’ manual segmentations achieved a Dice score of 0.820. Linear correlation coefficients for the T1, T1ρ, and T2∗ relaxations calculated using the automatic and manual segmentations ranged between 0.90 and 0.97, and there were no associated differences between the estimated average meniscal relaxation parameters. The deep learning models achieved segmentation performance equivalent to the inter‐observer variability of 2 radiologists.
Conclusion
The proposed deep learning‐based approach can be used to efficiently generate automatic segmentations and determine meniscal relaxations times. The method has the potential to help radiologists with the assessment of meniscal diseases, such as OA.
This paper addresses the dissipative asynchronous filtering problem for a class of Takagi-Sugeno fuzzy Markov jump systems in the continuous-time domain. The hidden Markov model is applied to ...describe the asynchronous situation between the designed filter and the original system. Based on the stochastic Lyapunov function, a sufficient condition is developed to guarantee the stochastic stability of the filtering error systems with a given dissipative performance. Two different methods for the existence of desired filter are established. Due to the Finsler's lemma, the second approach has fewer variables to decide and brings less conservatism than the first one. Finally, an example is provided to demonstrate the correctness and advantage of the proposed approaches.
This paper considers the distributed optimal path tracking control problem of autonomous ground vehicles (AGVs) with matched uncertainties under denial-of-service (DoS) attacks. First, to solve the ...uncertain system parameters, an inverse reinforcement learning (RL) technique is PROPOSED to seek the optimal controller instead of directly solving the robust control problem, which can ensure that the designed controller is globally optimal with respect to the proposal performance function. An off-policy RL algorithm is further proposed to learn the optimal control solution online without requiring any knowledge of the vehicle dynamics. Then, to lower the communication load among vehicles, a perception-based optimal resilient controller and its corresponding perception-based static deadband condition are developed, respectively. Moreover, the perception-based dynamic deadband control mechanism is further exploited to consider the secure path tracking control problem. The proposed algorithms verify that the RL-based optimal path tracking control can be solved, and the occurrence of the Zeno phenomenon can be avoided. Finally, a numerical simulation is demonstrated to verify the effectiveness of the proposed approach.
Bi2WO6 ordered porous film with open pores, an example of a photocatalytically active ternary metal oxide under visible‐light irradiation, is prepared using a simple and reproducible route. The ...ordered porous Bi2WO6 films exhibited much higher photocatalytic activity and photocurrent coversion efficiency than nonporous Bi2WO6 films under visible‐light irradiation (λ > 420 nm).
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