Differential graphical games for H∞ control of linear heterogeneous multiagent systems

Differential graphical games have been introduced in the literature to solve state synchronization problem for linear homogeneous agents. When the agents are heterogeneous, the previous notion of graphical games cannot be used anymore and a new definition is required. In this paper, we define a novel concept of differential graphical games for linear heterogeneous agents subject to external unmodeled disturbances, which contain the previously introduced graphical game for homogeneous agents as a special case. Using our new formulation, we can solve both the output regulation and H_∞ output regulation problems. Our graphical game framework yields coupled Hamilton‐Jacobi‐Bellman equations, which are, in general, impossible to solve analytically. Therefore, we propose a new actor‐critic algorithm to solve these coupled equations numerically in real time. Moreover, we find an explicit upper bound for the overall ‐gain of the output synchronization error with respect to disturbance. We demonstrate our developments by a simulation example.     

A context-aware adaptive learning system using agents

Evolution of Web technologies has made e-learning a popular common way of education and training. As an outcome, learning content adaptation has been the subject of many research projects lately. This paper suggests a framework for building an adaptive Learning Management System (LMS). The proposed architecture is based upon multi-agent systems and uses both Sharable Content Object Reference Model (SCORM) 2004 and semantic Web ontology for learning content storage, sequencing and adaptation. This system has been implemented upon a well known open-source LMS and its functionalities are demonstrated through the simulation of a scenario mimicing the real life conditions. The result reveals the system effectiveness for which it appears that the proposed approach may be very promising.     

Behavior of Small Particles from Process Gas Streams in Diffusion Furnaces

The deposition of small particles in the diffusion furnace environment was examined. A 6-ft-long and 6 1/4-in diameter quartz tube furnace was used. Particles ranging from 0.5 to 10 μm in diameter were generated and the deposition rate onto 5-in wafers in the furnace was measured as a function of gas stream flow rate, furnace temperature, and pressure. The measured deposition velocity ranged from 5×10^?5 to 5×10^?3 cm/s. The results of this study indicate that the deposition of particles decreases with increasing furnace tern perature. In addition, deposition increases as the wafer spacing increases and decreases as the wafers are placed further away from the entrance. Particles are found to deposit preferentially on the outer portion of the wafers. Owing to the flow pattern in the diffusion furnace, deposition of particulates is higher at the top of the wafer. The electrostatic charge effects were found to be insignificant.     

Micropatterned nanocrystalline zinc oxide thin films obtained through metal-loaded hydrogels

The paper describes the preparation of micropatterned zinc oxide films through a synthetic route based on the thermal degradation of metal-loaded poly(ethylene glycol)-based hydrogels. This approach requires very simple apparatuses and involves only simple, inexpensive and environmentally friendly chemicals. Highly transparent and crack free nanocrystalline films were obtained through this route. The evolution of the films during the thermal degradation and the influence of synthesis parameters on the film characteristics were investigated by thermal analysis, X-ray grazing incidence diffraction, scanning electron microscopy, atomic force microscopy and micro-Raman. The response toward reducing gasses was tested at different temperatures. Finally, the micropatterning of ZnO films through soft lithography has been characterized.     

H∞‐output regulation of linear heterogeneous multiagent systems over switching graphs

In this paper, we analyze H_∞‐output regulation of linear heterogeneous multiagent systems. The agents are subject to modeled and unmodeled disturbances and communicate over a switching graph. We derive a sufficient condition that guarantees H_∞ output regulation for the mentioned setup. This sufficient condition places requirements on both the single‐agent systems and the switching graph. The requirement on the single‐agent systems is an H_∞‐criterion that should be satisfied by a proper design of the controller. Meanwhile, the switching graph needs to be maximally connected. Moreover, we derive an upper bound for the overall ‐gain of the output synchronization error with respect to the unmodeled disturbances over a fixed communication graph. We illustrate our technical developments by a simulation example.     

Improvement of PMMA electron-beam lithography performance in metal liftoff through a poly-imide bi-layer system

Poly(methyl methacrylate) (PMMA) is a commonly used resist for electron-beam lithography. Some primary reasons for the widespread popularity of PMMA include high resolution and low cost. Single layer PMMA has notably poor characteristics in metal liftoff and sub-15 nm resolution as well as poor line edge roughness. Standard problems with liftoff such as tags, feature removal and lack of solvent penetration were alleviated with a poly-imide lift-off layer which increased resolution and allowed better liftoff. The effect of dense feature proximity over-dose was also reduced with this method. Single lines in metal as small as 23 nm were achieved and denser patterns were resolved with a pitch of 50 nm. These results increase the utility of PMMA as a nanolithographic material for fabricating small metallic features by the use of a liftoff technique.     

Surfactant Assisted Dispersion and Adhesion Behavior of Carbon Nanotubes on Cu-Zr and Cu-Zr-Al Amorphous Powders

Carbon nanotubes （CNTs） were dispersed in gas atomized Cu47.5Zr47.5Al5 （CZA） and CusoZrso （CZ） amorphous powders, in an effort to elucidate the mechanisms of adhesion of CNTs onto amorphous metallic powders. CNTs were homogenously dispersed in water using a zwitterionic （ZW） surfactant. Then CZA and CZ powders were submersed in the ZW-CNTsuspensions with varying amounts of dwell time in an ultrasonic bath. The ZW-CNT- metal powder suspensions were dried, and CNT-metal composite powders were obtained after decomposition of the surfactant by calcination. Zeta potential measurements on ZW-CNT-metal powder suspensions and scanning electron microscopy investigation into the CNT-metal composite powders both indicated an ideal dwell time, for a specific alloy composition, of metallic powders in ZW-CNT suspension to achieve optimal adhesion of CNTs onto amorphous metallic powder surfaces. The results are rationalized on the basis of hydrolysis of metal ions into suspension creating a net positive charge on the metallic powder surfaces, and the interaction between the charged powder surfaces and the charged hydrophilic head groups of ZW, which has the other end attached to CNTs.     

Output regulation of heterogeneous linear multi‐agent systems with differential graphical game

This paper addresses output regulation of heterogeneous linear multi‐agent systems. We first show that output regulation can be achieved through local controller design, then we formulate output regulation in the graphical game framework. To solve output regulation of heterogeneous linear multi‐agent system in the graphical game framework, one needs to derive a solution to the coupled Hamilton–Jacobi equations. Both offline and online algorithms are suggested for that solution. Using the online method, the profile policy converges to a Nash Equilibrium. Besides, it is shown that the graphical formulation is robust to the multiplicative uncertainty satisfying an upper bound and it has an infinite gain margin. Copyright © 2015 John Wiley & Sons, Ltd.