This paper briefly reviews the current status of the most popular methods for combined quantum mechanical/molecular mechanical (QM/MM) calculations, including their advantages and disadvantages. There is a special emphasis on very general link-atom methods and various ways to treat the charge near the boundary. Mechanical and electric embedding are contrasted. We consider methods applicable to gas-phase organic chemistry, liquid-phase organic and organometallic chemistry, biochemistry, and solid-state chemistry. Then we review some recent tests of QM/MM methods and summarize what we learn about QM/MM from these studies. We also discuss some available software. Finally, we present a few comments about future directions of research in this exciting area, where we focus on more intimate blends of QM with MM.

This paper studies the platoon formation control problem for unmanned surface vehicles, in the presence of modeling uncertainties and time-varying external disturbances. The control objective is to make the vehicular platoons proceed along a given trajectory while maintaining a desired line-of-sight (LOS) range between each vehicle and its predecessor. To provide transient performance specifications on formation errors, including LOS range and angle errors, we enforce prescribed performance guarantees in the control design. The prescribed performance guarantees mean that formation errors evolve always within the predefined regions that are bounded by exponentially decaying functions of time. Using prescribed performance control methodology, neural network approximation, disturbance observers, dynamic surface control technique, and Lyapunov synthesis, we propose an adaptive formation control that ensures internal stability of closed-loop systems with guaranteed prescribed performance. Meanwhile, both collision avoidance and connectivity maintenance between two consecutive vehicles are guaranteed during the whole operation. The proposed formation control is decentralized in the sense that the control action on each vehicle depends only on information from its immediate predecessor. Simulation results demonstrate the performance of the proposed control.

Supply chain systems are network systems with several subchains each of which consists of facilities and distribution entities (suppliers, manufacturers, distributors, and retailers), and thus such systems can be viewed as multiagent systems. Consensus or coordination of multiple subchains is crucial for a stable market supply, especially in the case of some subchains suffering from production interruption, or losing connection with others, which become isolated subchains in some time period due to irresistible reasons. Once some unspecified isolated subchains appear, the topology structure of the system will be changed, and thus the multiagent-based supply chain system can be modeled as a switched system. This paper aims to investigate the problem of ${H_\infty }$ consensus for multiagent-based supply chain systems under switching topology and uncertain demands. To achieve the consensus of the system, switching controller is designed in which both production rate and distributed consensus protocol are considered. Sufficient conditions are given such that the whole system reaches consensus and desirable attenuation of bullwhip effect with an average dwell time approach, which allows some subchains to be isolated in some time periods. Finally, a simulation example is presented to illustrate the effectiveness of the proposed method.

In this paper, both the asymptotic stability and l ^∞ persistent disturbance attenuation issues are investigated for a class of networked control systems (NCSs) under bounded uncertain access delay and packet dropout effects. The basic idea is to formulate such NCSs as discrete-time switched systems with arbitrary switching. Then the NCSs' stability and performance problems can be reduced to the corresponding problems of such switched systems. The asymptotic stability problem is considered first, and a necessary and sufficient condition is derived for the NCSs' asymptotic stability based on robust stability techniques. Secondly, the NCSs' l ^∞ persistent disturbance attenuation properties are studied and an algorithm is introduced to calculate the l ^∞ induced gain of the NCSs. The decidability issue of the algorithm is also discussed. A network controlled integrator system is used throughout the paper for illustration.