All agents being informed and the virtual leader traveling at a constant velocity are the two critical assumptions seen in the recent literature on flocking in multi-agent systems. Under these ...assumptions, Olfati-Saber in a recent IEEE Transactions on Automatic Control paper proposed a flocking algorithm which by incorporating a navigational feedback enables a group of agents to track a virtual leader. This paper revisits the problem of multi-agent flocking in the absence of the above two assumptions. We first show that, even when only a fraction of agents are informed, the Olfati-Saber flocking algorithm still enables all the informed agents to move with the desired constant velocity, and an uninformed agent to also move with the same desired velocity if it can be influenced by the informed agents from time to time during the evolution. Numerical simulation demonstrates that a very small group of the informed agents can cause most of the agents to move with the desired velocity and the larger the informed group is the bigger portion of agents will move with the desired velocity. In the situation where the virtual leader travels with a varying velocity, we propose modification to the Olfati-Saber algorithm and show that the resulting algorithm enables the asymptotic tracking of the virtual leader. That is, the position and velocity of the center of mass of all agents will converge exponentially to those of the virtual leader. The convergent rate is also given.
In this paper, the event-triggered semiglobal consensus problem is investigated for general linear multi-agent systems subjected to input saturation, by utilizing the algebraic Riccati equation-based ...low-gain feedback technique. Two scenarios for systems with or without updating delays are considered, and fully distributed event-triggered control schemes are proposed to guarantee the semiglobal consensus of the connected systems, in which each agent is asymptotically null controllable with bounded controls. Strictly positive lower bounds for both the sampling intervals and the updating delays are captured for each agent to eliminate the Zeno behaviors in these two event-triggered processes. Finally, the effectiveness of these event-triggered control schemes are verified by simulations.
Agricultural greenhouses (AGs) are an important facility for the development of modern agriculture. Accurately and effectively detecting AGs is a necessity for the strategic planning of modern ...agriculture. With the advent of deep learning algorithms, various convolutional neural network (CNN)-based models have been proposed for object detection with high spatial resolution images. In this paper, we conducted a comparative assessment of the three well-established CNN-based models, which are Faster R-CNN, You Look Only Once-v3 (YOLO v3), and Single Shot Multi-Box Detector (SSD) for detecting AGs. The transfer learning and fine-tuning approaches were implemented to train models. Accuracy and efficiency evaluation results show that YOLO v3 achieved the best performance according to the average precision (mAP), frames per second (FPS) metrics and visual inspection. The SSD demonstrated an advantage in detection speed with an FPS twice higher than Faster R-CNN, although their mAP is close on the test set. The trained models were also applied to two independent test sets, which proved that these models have a certain transability and the higher resolution images are significant for accuracy improvement. Our study suggests YOLO v3 with superiorities in both accuracy and computational efficiency can be applied to detect AGs using high-resolution satellite images operationally.
We investigate second-order consensus of multiple nonlinear dynamical mobile agents with a virtual leader in a dynamic proximity network. We assume that only a small fraction of agents in the group ...have access to the information about the position and velocity of the virtual leader through, for example, certain pre-designed communication mechanism such as wireless broadcasting or sensing. To avoid fragmentation, we propose a connectivity-preserving second-order consensus algorithm. Under the assumption that the initial network is connected, we introduce local adaptation strategies for both the weights on the velocity navigational feedback and the velocity coupling strengths that enable all agents to synchronize with the virtual leader even when only one agent is informed, without requiring any knowledge of the agent dynamics. We finally provide some convincing simulation results to illustrate the theoretical results.
We consider distributed state estimation over a resource-limited wireless sensor network. A stochastic sensor activation scheme is introduced to reduce the sensor energy consumption in ...communications, under which each sensor is activated with a certain probability. When the sensor is activated, it observes the target state and exchanges its estimate of the target state with its neighbors; otherwise, it only receives the estimates from its neighbors. An optimal estimator is designed for each sensor by minimizing its mean-squared estimation error. An upper and a lower bound of the limiting estimation error covariance are obtained. A method of selecting the consensus gain and a lower bound of the activating probability is also provided.
This paper studies the observer-based leader-following consensus of a linear multiagent system on switching networks, in which the input of each agent is subject to saturation. Based on a low-gain ...output feedback method, distributed consensus protocols are developed. Under the assumptions that the networks are connected or jointly connected and that each agent is asymptotically null controllable with bounded controls and detectable, semiglobal observer-based leader-following consensus of the multiagent system can be reached on switching networks. A numerical example is presented to illustrate the theoretical results.
Common prosperity stands as a pivotal concept and objective within China's socialism with distinctive characteristics, serving as a fundamental assurance and basis for ensuring its people's happiness ...and comprehensive development. This research employs a Coupled Coordination Degree Model to construct a common prosperity Index using data from China between 2010 and 2020. The study investigates the influence of innovation and entrepreneurship on common prosperity while examining the regulating roles played by the government and market during this process. The outcomes demonstrate that innovation substantially facilitates the realization of common prosperity. The relationship between entrepreneurship and common prosperity follows a positive "U"-shaped curve, where entrepreneurship significantly contributes to common prosperity upon reaching a particular scale. Further investigations reveal heterogeneity in the impact of innovation and entrepreneurship on common prosperity. Specifically, innovation significantly contributes to common prosperity in the northern regions, whereas entrepreneurship has a noteworthy impact on common prosperity in the southern regions. Moreover, it is worth noting that both innovation and entrepreneurship have a significant influence on common prosperity in areas characterized by low economic development levels and a scarcity of fixed capital. The fiscal effects of the government attenuate the promoting effect of innovation on common prosperity but enhance the adverse influence of entrepreneurship. On the contrary, market mechanisms mitigate the negative impact of entrepreneurship on common prosperity. Consequently, achieving common prosperity requires strengthened regional innovation cooperation, encouraging advanced regions to lead underdeveloped regions, and leveraging the regulatory roles of both the government and the market, thus progressing gradually towards common prosperity.
In coordinative control of a network of multi-agent systems, to guarantee the stability of the coordinated motion, a basic assumption typically is that the underlying topology of the network can ...maintain its connectivity frequently enough during the motion evolution. However, for a given set of initial conditions, this assumption is very difficult to satisfy and verify. In particular, the connectivity of the initial network generally cannot guarantee the connectivity of the network throughout the evolution. In this paper, we propose a rendezvous protocol with double-integrator dynamics, which combines the functions of motion control and connectivity preservation. This protocol can enable the group of mobile agents to converge to the same position and move with the same velocity while preserving the connectivity of the whole network during the evolution if the initial network is connected. We find that there is a trade-off between the maximum overshoot and the settling time of the velocity convergence. Furthermore, we investigate the rendezvous protocol with a virtual leader and show that all agents can asymptotically attain a desired velocity even if only one agent in the team has information about the virtual leader. We finally show some numerical simulations to verify and illustrate the theoretical results.
Enhancement and continuous control of the excitonic valley polarization in electrostatically doped monolayer WSe2 are demonstrated. Under excitation with circularly polarized light, 20% valley ...polarization of excitons around the charge neutrality condition at 70 K is increased to 40% by modulating the electron/hole density up to 2 × 1012 cm−2. This increase originates from slow valley relaxation for neutral exciton between the K and −K valleys owing to screening of long‐range e–h exchange interactions by doped carriers. The gate‐dependences of the exciton valley polarization at various temperatures are reproduced by theoretical calculations, which holds potential for next‐generation valleytronic devices continuously controlled by an applied bias voltage.
Excitonic valley polarization in electrostatically doped monolayer WSe2 is controlled by modulating the carrier density. Screening of long‐range e–h exchange interactions by the doped carriers suppresses valley relaxation for neutral excitons between the K and −K valleys.
In this paper, we revisit the synchronization problems for coupled harmonic oscillators in a dynamic proximity network. Unlike many existing algorithms for distributed control of complex dynamical ...networks that require explicit assumptions on the network connectivity, we show that the coupled harmonic oscillators can always be synchronized, without imposing any network connectivity assumption. Moreover, we also investigate the synchronization with a leader and show that all harmonic oscillators can asymptotically attain the position and velocity of the leader, again without any assumption on connectivity of the followers. Numerical simulation illustrates the theoretical results.
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