Vision-Based Adaptive Prescribed-Time Control of UAV for Uncooperative Target Tracking with Performance Constraint

This paper discusses the uncooperative target tracking control problem for the unmanned aerial vehicle(UAV)under the performance constraint and scaled relative velocity constraint,in which the states of the uncooperative target can only be estimated through a vision sensor.Considering the limited detection range,a prescribed performance function is designed to ensure the transient and steady-state performances of the tracking system.Meanwhile,the scaled relative velocity constraint in the dynamic phase is taken into account,and a time-varying nonlinear transformation is used to solve the constraint problem,which not only overcomes the feasibility condition but also fails to violate the constraint boundaries.Finally,the practically prescribed-time stability technique is incorporated into the controller design procedure to guarantee that all signals within the closed-loop system are bounded.It is proved that the UAV can follow the uncooperative target at the desired relative position within a prescribed time,thereby improving the applicability of the vision-based tracking approach.Simulation results have been presented to prove the validity of the proposed control strategy.

One-to-Any Command and Control Model:Precisely Coordinated Operation on Uncooperative Controlled Nodes

New precisely cooperative attacks, such as the coordi- nated cross plane session termination （CXPST） attack, need thou- sands upon thousands machines to attack diverse selected links simultaneously with the given rate. However, almost all command and control（C＆C） mechanisms only provide publishing one com- mand to the whole once, so-called one-to-all C＆C model, and are not productive to support CXPST-alike attacks. In this paper, we present one-to-any C＆C model on coordination among the unco- operative controlled nodes. As an instance of one-to-any C＆C model, directional command publishing （DCP） mechanism lever- aging on Kademlia is provided with a range-mapping key creating algorithm for commands to compute the publishing range and a statistically stochastic node querying scheme to obtain the com- mands immediately. With theoretical analysis and simulation, it is indicated that one-to-any C＆C model fits for precisely coordi- nated operation on uncooperative controlled nodes with least complexity, better accuracy and efficiency. Furthermore, DCP mechanism can support one-to-all command publishing at the same time. As an example of future C＆C model, studying on one-to-any C＆C model may help to promote the development of more efficient countermeasures.

An ab initio study on boundaries for characterizing cooperative effect of hydrogen bonds by intermolecular compression

The cooperative effect plays a significant role in understanding the intermolecular donor-acceptor interactions of hydrogen bonds(H-bonds, D-H···A). Here, using the coupled-cluster singles and doubles with perturbative triple excitations(CCSD(T)) method of high-precision ab initio calculations, we show that the intermolecular H-bonded systems with different D and A atoms reproduce the structural changes predicted by the well-known cooperative effect upon intermolecular compression. That is, with decreasing intermolecular distance, the D-H bond length first increases and then decreases, while the H···A distance decreases. On the contrary, when D and A are the same, as the intermolecular distance decreases, the D-H bond length decreases without increasing. This obvious difference means that the cooperative effect may not be generally characterized by intermolecular compression. Interestingly, further analyses of many intermolecular systems confirm that this failure has boundaries, i.e., cooperative systems at their respective equilibrium positions have a smaller core-valence bifurcation(CVB) index(<0.022) and stronger binding energies(>0.25 eV), showing a clear linear inverse relationship related to H-bond strength. These findings provide an important reference for the comprehensive understanding of H-bonds and its calculation methods.