Aerial Swarm Defense by StringNet Herding: Theory and Experiments

This paper studies a defense approach against one or more swarms of adversarial agents. In our earlier work, we employed a closed formation (“StringNet”) of defending agents (defenders) around a swarm of adversarial agents (attackers) to confine their motion within given bounds, and guide them to a safe area. The adversarial agents were assumed to remain close enough to each other, i.e., within a prescribed connectivity region. To handle situations when the attackers no longer stay within such a connectivity region, but rather split into smaller swarms (clusters) to maximize the chance or impact of attack, this paper proposes an approach to learn the attacking sub-swarms and reassign defenders toward the attackers. We use a “Density-based Spatial Clustering of Application with Noise (DBSCAN)” algorithm to identify the spatially distributed swarms of the attackers. Then, the defenders are assigned to each identified swarm of attackers by solving a constrained generalized assignment problem. We also provide conditions under which defenders can successfully herd all the attackers. The efficacy of the approach is demonstrated via computer simulations, as well as hardware experiments with a fleet of quadrotors.

Finite groups in which every cyclic subgroup is self-normalizing in its subnormal closure

For a given prime p, a finite group G is said to be a {\widetilde{\mathcal{C}}_{p}} -group if every cyclic p-subgroup of G is self-normalizing in its subnormal closure. In this paper, we get some descriptions of {\widetilde{\mathcal{C}}_{p}} -groups, show that the class of {\widetilde{\mathcal{C}}_{p}} -groups is a subgroup-closed formation and that {O^{p^{\prime}}(G)} is a solvable p-nilpotent group for every {\widetilde{\mathcal{C}}_{p}} -group G. We also prove that if a finite group G is a {\widetilde{\mathcal{C}}_{p}} -group for all primes p, then every subgroup of G is self-normalizing in its subnormal closure.

Design and flight-stability analysis of a closed fixed-wing unmanned aerial vehicle formation controller

This article addresses a flight-stability problem for the multiple unmanned aerial vehicles cooperative formation flight in the process of the closed and high-speed flight. The main objective is to design a cooperative formation controller with known external factors, and this controller can keep the consensus of attitude and position and reduce the communication delay between any two unmanned aerial vehicles and increase unmanned aerial vehicles formation cruise time under the known external factors. Known external factors are taken into consideration, and longitude maneuvers using nonlinear thrust vectors were employed with unsteady aerodynamic models, according to the attitude and position of unmanned aerial vehicles, which were employed as corresponding input signals for studying the dynamic characteristics of unmanned aerial vehicles formation flight. In addition, the relative distance between any two unmanned aerial vehicles was not allowed to exceed their safe distance so that the controller could perform collision avoidance. An analysis of formation flight distance error shows that it converged to a fixed value that well ensured unmanned aerial vehicles formation flight stability. The experimental results show that the controller can improve the speed of a closed formation effectively and maintain the stability of formation flight, which provides a method for closed formation flight controller design and collision avoidance for any two unmanned aerial vehicles. Meanwhile, the effectiveness of proposed controller is fully proved by semi-physical simulation platform.

On a class of finite soluble groups

The aim of this paper is to study the class of finite groups in which every subgroup is self-normalising in its subnormal closure. It is proved that this class is a subgroup-closed formation of finite soluble groups which is not closed under taking Frattini extensions and whose members can be characterised by means of their Carter subgroups. This leads to new characterisations of finite soluble T-, PT- and PST-groups. Finite groups whose p-subgroups, p a prime, are self-normalising in their subnormal closure are also characterised.

On groups with formational subnormal Sylow subgroups

We investigate a finite groupGwith{\mathfrak{F}}-subnormal Sylow subgroups, where{\mathfrak{F}}is a subgroup-closed formation and{\mathfrak{A}_{1}\mathfrak{A}\subseteq\mathfrak{F}\subseteq\mathfrak{N}% \mathcal{A}}. We prove thatGis soluble and the derived subgroup of each metanilpotent subgroup is nilpotent. We also describe the structure of groups in which every Sylow subgroup is{\mathfrak{F}}-subnormal or{\mathfrak{F}}-abnormal.

A note on solubly saturated formations of finite groups

The main aim of this note is to give a criterion for a subgroup-closed formation to be solubly saturated, which we hope may provide a useful proving ground for outstanding questions about this family of formations.

Research of High Grade HIC-Resistant Pipeline Steel

Carry out research on the processes, structures and properties of the X70 corrosion-resistant pipeline steel and analyze the mechanism of the hydrogen induced cracking. The results show that: the developed steel not only has excellent mechanical properties, but also has good resistance to H2S corrosion. Microstructure of the X70 corrosion-resistant pipeline is mainly the acicular ferrite and granular bainite, with well-closed formation and fine grains. Hydrogen Induced Cracking (HIC) begins with the appearance of the hydrogen blistering on the specimen surface, and cracks generated by the hydrogen blistering gradually extend inward from the surface along the grain boundary, diffuse inside the specimen gradually, and finally form hydrogen induced cracking.

On ℱ-residuals of finite groups

We prove that there exists a soluble, saturated and s-closed formation ℱ of groups such that the class (Gℱ | G is a group, Gℱ is the ℱ-residual of G) is not closed under subdirect products. This result a negative answer to an open problems recently proposed by L.A. Shemetkov in 1998.