Decentralized weighted control for a class of large‐scale systems with multi‐modes

In this paper, the control synthesis problem for a class of large‐scale systems with multi‐modes that are called large‐scale switched systems is addressed. By introducing the concept of decentralized switching signal and the relevant decentralized average dwell time, the asymptotic stability and weighted ?₂ gain performance are investigated. It should be noted that the decentralized switching covers general switching cases for large‐scale switched systems, namely, it admits both time‐dependent switching signal and arbitrary switching signal blended in the decentralized switching. Then, on the basis of the analysis results, the decentralized weighted control scheme including state feedback controller gains and switching signals is studied. Several design algorithms are proposed to meet different controller design problems. Finally, numerical examples are provided to illustrate theoretical findings within this paper. Copyright © 2013 John Wiley & Sons, Ltd.     

Decentralized output feedback stabilization for a class of large‐scale feedforward nonlinear time‐delay systems

This paper is concerned with the decentralized stabilization problem for a class of large‐scale feedforward nonlinear time‐delay systems. The uncertain nonlinearities involved in the systems are assumed to be bounded by continuous functions of the inputs and delayed inputs multiplied by unmeasured states and delayed states. An observer‐based decentralized output feedback control scheme is proposed by using the dynamic gain control design approach. On the basis of the Lyapunov–Krasovskii stability theory, the global asymptotic stability of the closed‐loop control system is proved. Contrary to many existing control designs for feedforward nonlinear systems, the celebrated forwarding design and saturation design are not utilized here. An example is finally given to demonstrate the effectiveness of the proposed design procedure. Copyright © 2013 John Wiley & Sons, Ltd.     

浅谈校园网大规模移动自组的网络安全技术

随着社会经济与科技的迅速发展,移动通信技术与人们生活及工作之间的联系越发紧密,移动通信技术也得到其应有的发展.在整个环境背景下,移动自组网络技术也开始出现于人们的生活中.移动自组网络技术开始应用于如军事、医疗以及电子商务等多个领域,在校园网中的应用也较为广泛.文章首先对移动自组网络进行了阐述说明,之后对校园网移动自组网络安全技术进行了深入的分析研究,以此提升人们对校园网大规模移动自组网络安全技术的认识.     

Correlations between characteristics of maximum influence and degree distributions in software networks

Software systems can be represented as complex networks and their artificial nature can be investigated with approaches developed in network analysis.Influence maximization has been successfully applied on software networks to identify the important nodes that have the maximum influence on the other parts.However,research is open to study the effects of network fabric on the influence behavior of the highly influential nodes.In this paper,we construct class dependence graph(CDG)networks based on eight practical Java software systems,and apply the procedure of influence maximization to study empirically the correlations between the characteristics of maximum influence and the degree distributions in the software networks.We demonstrate that the artificial nature of CDG networks is reflected partly from the scale free behavior:the in-degree distribution follows power law,and the out-degree distribution is lognormal.For the influence behavior,the expected influence spread of the maximum influence set identified by the greedy method correlates significantly with the degree distributions.In addition,the identified influence set contains influential classes that are complex in both the number of methods and the lines of code(LOC).For the applications in software engineering,the results provide possibilities of new approaches in designing optimization procedures of software systems.     

正弦波下砂岩ms级损伤预测模型

为获得毫秒(ms)级正弦波损伤变量预测模型,对岩样在不破坏情况下进行了不同波形不同频率的轴向力加卸载试验。提出了不同步时间段的定义,进而获得不同峰值荷载下不考虑不同步时间条件下的动态泊松比分别与即时荷载、即时横向长度、即时轴向高度之间的线性关系,从而得到线性关系中系数与峰值荷载间的拟合公式,即可联立不同已知条件,通过少量几个加载力峰值下的试验数据,对任意峰值荷载下动态泊松比与相关参数间的线性关系进行预测。以此为基础研究得到,在误差允许的范围内,采用动态泊松比与即时横向长度的线性关系,推导出体积应变、损伤变量的计算公式和方法,可以很好地对加卸载过程中岩样的体积应变、损伤的变化做出ms级的精确预测,也为在已知少量循环试验下获得岩石动态参数,即可对ms级的损伤进行精确预测的模型提供了方法。     

时间尺度对平原感潮河网水动力水质模拟精度的影响

为探究不同时间尺度边界入流条件对平原感潮河网水动力水质模型模拟精度的影响,以典型平原感潮河网地区的张家港市中部为研究区域,结合野外同步监测数据、自动高频监测数据、常规监测资料等构建了水动力水质模型进行模拟分析。结果表明:时间尺度、开始取值时刻以及调度情况均会影响模拟精度;研究区域边界入流条件、水动力模拟结果和水质模拟结果可信的最大时间尺度为1 h,水质模拟精度优于水动力模拟精度。     

任务序列强度感知的大规模集群服务器控制模型

异构云数据中心各类服务器的控制成本和性能上的差异将影响其运维管理成本及QoS博弈平衡关系,针对任务序列强度具有的时效性,提出了任务序列强度感知的大规模任务调度模型。依据当前到达数据中心的任务序列的强度以及集群中服务器的当前状态,在任务调度中强调节约服务器运维管理成本和各服务器负载均衡的基础上实现优化数据中心对任务序列处理的平均响应时间和系统的吞吐量。通过对实验结果的分析,验证了集群服务器控制模型在任务调度中的可信度大于95%,同时通过与当前应用广且具代表性的算法——最短任务优先,公平分发机制进行比较分析,其效果是三者中最好的,也验证了模型的有效性和可行性。     

High-temperature oxidation of pure titanium in CO2 and Ar-10%CO2 atmospheres

The oxidation behavior of pure titanium has been investigated in the temperature range of 1000 K to 1300 K in CO₂ or Ar-10%CO₂. Optical microscopy, electron probe microanalyses, and X-ray measurements on the oxide scales formed during oxidation indicate that their structures are nearly independent of temperature and the corrosion atmosphere. The scales consisted of two layers, an external one and an internal one, having a rutile (TiO₂) structure. The parabolic rate law was confirmed for growth of the external scale and the permeation depth of oxygen in titanium with apparent activation energies of 266 and 226 kJ/mol, respectively. The rate-determining diffusion species in the oxidation processes are discussed.     

A high-temperature oxidation-resistant Fe-Mn-Al-Si alloy

To develop satisfactory alloys without Cr or Ni for high-temperature application up to 1100C, three alloys based on Fe-10%Al-Si with differing fourth (or fifth) element additions were oxidized in air at 1100°Cfor 24 hr. A low carbon, Fe-30Mn-10Al-Si alloy exhibited excellent high-temperature oxidation resistance. The total weight gain for 24 hr oxidation in air at 1100°C was only 1.03 mg/cm ². After air oxidation for 6 days at 1100°C, no nodule formation or breakthrough oxidation occurred. Post-oxidation SEM and EDAX examination showed that a thin, compact, protective alumina scale formed on the alloy.Visiting Scientist (People's Republic of China).     

Microcrack generation and its healing in the oxide scale formed on Fe-Cr alloys

Fe -base alloys containing 5, 10, and 20 wt. % Cr were oxidized in a stream of O₂ at 750 and 900°C up to 264 hr. A sulfur decoration method was applied to detect the cracks generated in the scale during oxidation. This method revealed frequent crack generation and its healing in the scale. In the case of low-Cr alloys, the cracks are filled up with newly formed Fe-rich oxide but may be regenerated during further oxidation. Cracks are generated in the scale on an Fe-20Cr alloy also, although this alloy is not so severely attacked because of rapid healing.