The Formation of Nanoscale Closed Graphene Surfaces during Fullerite C60 Hot Isostatic Pressing

The fullerite C60 modified by hot isostatic pressing (HIP) at 0.1 GPa in argon near and beyond its thermal stability region (920–1270 K temperature interval) was studied by X-ray diffractometry, Raman spectroscopy, ultra soft X-ray photoelectron and near edge X-ray absorption fine structure spectroscopy. It was found that the C60 molecules merge into closed nanocapsules with a graphene surface during the thermal treatment. The conducted studies showed that using HIP treatment of the fullerite C60, it is possible to obtain a chemically resistant material with a high hardness and elasticity, as well as a density lower than that of the graphite. This new material, consisting of closed graphene nanocapsules 2–5 nm in size, formed by sp2 covalent bonds between carbon atoms is promising for various applications, and as a basis for the synthesis of new composite materials.

Analyzing the Chinese Telecommunication Industry Based on Oligopoly Game and Dynamic Evolution

In this paper, we consider the impact of the product price, service level and delay parameters on the operation of enterprises in the current Chinese telecommunications industry. A three-oligarch game model is established, where system parameters are taken as important factors affecting the development of the involved companies. By improving their service levels, the three oligarchs could plunder the market of each other, but also enhance the reputation of the industry, thus bringing more communication data usage. In the paper, firstly we analyze the static Nash equilibrium, especially the impacts of competition intensity and service cost coefficiency. Then, we analyze the stability and evolution behavior of the system under the dynamic game. We found that the increase of competition intensity and cost coefficiency has adverse effects on the stability region. Finally, we show that a delay decision of a single company has a positive impact on its own profits, but not conducive to its own stability region and the profits of the opposing oligarchs, nor to the total profit.

Tuning proportional-integral controllers based on new analytical methods for finding centroid of stability locus for stable/unstable first-order plus dead-time processes

The simplicity of the proportional-integral controller makes it very popular in many practical engineering applications. In the literature, several approaches have been introduced for tuning proportional-integral controllers by calculating the centroid of the stability region. However, all those approaches depend on graphical plottings which are time-consuming. Also, the design procedure has to be redone as the transfer function changes. Here, two new analytical methods are proposed to obtain the centroid of the stability region for the proportional-integral controllers to control a time delay process which can be modeled by a stable or unstable first-order plus dead-time model. The methods introduced eliminate the compulsory procedure of plotting the stability region. The efficiency of the suggested methods has been studied by conducting a robustness analysis and studying several simulation examples.

Generic Noninteger Order Controller for Time-Delay Systems

This paper focuses on the problem of fractional controller P I stabilization for a first-order time-delay systems. For this reason, we utilize the Hermite–Biehler and Pontryagin theorems to compute the complete set of the stabilizing P I λ parameters. The widespread industrial utilization of PID controllers and the potentiality of their noninteger order representation justify a timely interest in P I λ tuning techniques. Step responses are calculated through K p , K i , l a m b d a parameters inside and outside stability region to prove the method efficiency.