An LMI-based approach for robust stabilization of time delay systems containing saturating actuators

Email: elhaous_fati{at}yahoo.fr Corresponding author. Email: elh_tissir{at}yahoo.fr Received on September 8, 2005; Accepted on July 24, 2006 This paper deals with the problem of robust stabilization foruncertain systems with input saturation and time delay in thestate. The parameter uncertainties are time-varying and unknownbut are norm bounded. Sufficient conditions obtained via a linearmatrix inequality formulation are stated to guarantee the localstabilization. The method of synthesis consists in determiningsimultaneously a state feedback control law and an associateddomain of safe admissible states for which the stability ofthe closed-loop system is guaranteed when control saturationseffectively occur. Numerical examples are used to demonstratethe effectiveness of the proposed design technique.     

Non-linear robust boundary control of the Kuramoto-Sivashinsky equation

^** Email: krsakthivel{at}rediffmail.com^*** Email: hiroshi{at}ces.kyutech.ac.jp This paper considers the problem of robust global stabilizationof the Kuramoto–Sivashinsky equation subject to Neumannand Dirichlet boundary conditions. The aim is to derive non-linearrobust boundary control laws which make the system robustlyglobally asymptotically stable in spite of uncertainty in boththe instability parameter and the anti-diffusion parameter.A unique approach this paper introduces for achieving the requiredrobustness is spatially dependent scaling of uncertain elementsin Lyapunov-based stabilization. An important advantage of thisapproach is flexibility to obtain robust control laws with smallcontrol effort. The control laws can be implemented as Dirichlet-likeboundary control as well as Neumann-like boundary control. Furthermore,it is shown that they guarantee the stability and boundednessin terms of both L₂ and L.     

Effects of Aromatic Stabilization Energies on Photochromism of New Asymmetrical Azaindole‐Containing Diarylethenes

Three new asymmetrical diarylethenes containing an azaindole moiety and a variable heteroaryl ring have been synthesized. Their properties, such as photochromism, fatigue resistance, thermal stability, acidichromism, and fluorescence, were systematically investigated to elucidate the effects of aromatic stabilization energies (ASE) of the heteroaryl moieties. The results indicated that thermal stability decreased with the increment of the aromatic stabilization energies of the variable heteroaryl rings in the order of thiazyl<thienyl<pyrrolyl. Moreover, the dual switching behaviors of these azaindole‐containing diarylethenes were also studied by the stimulation of acid/base and light. Addition of trifluoroacetic acid to the solutions of these diarylethenes resulted in obvious hypochromic shifts, and their N‐protonated forms also exhibited favorable photochromism.     

浓香花生风味物质研究存在问题及对策探析

浓香花生油因其独特风味深受消费者喜爱,拥有广阔的市场前景.探析浓香花生油风味物质研究中存在的问题,分别论述了目前浓香花生油风味物质在准确定性定量、全面系统评价和风味形成机理研究方面存在的不足,就上述问题提出了相应的对策,并对未来该领域研究前景进行了展望.     

The Impact of Resonance Stabilization on the Intramolecular Hydrogen‐Atom Shift Reactions of Hydrocarbon Radicals

A series of intramolecular H‐atom shift reactions of both alkenyl and allylic radicals were investigated by using CBS‐QB3 electronic structure calculations. In the first set of reactions, an alkyl radical site was converted into an allylic radical site. In the second set, an allylic radical was converted into another allylic radical. The results are discussed in the context of a Benson‐type model to examine the impact of the transition‐state partial resonance stabilization on both the activation energies and the pre‐exponential factors. In most cases, the differences in the activation energies relative to those for the analogous alkyl radicals are primarily due to the barriers of the bimolecular reaction component of the activation energy. For the first set of reactions, there is additional entropy loss relative to the alkyl radical analogues. This additional loss of entropy may be smaller than some previous estimates. The pre‐exponential factors for the second set of reactions are generally similar to those of the analogous alkyl radical reactions (once the double bond in the transition state is accounted for).     

DNA酶: 筛选、 生物传感及展望

综述了脱氧核糖核酸酶(DNA酶)的起源及分离富集策略, 对比了DNA酶与核糖核酸酶(RNA酶)及蛋白酶的相似点和不同之处, 并重点讨论了产物捕获和对冲抵消等策略对筛选获得DNA酶的独到之处; 同时系统回顾了近年来分离出的可特异感应各种金属离子或生物样本(包括细菌、 细胞等), 从而能在特定位点切割RNA底物的DNA酶探针; 阐述了DNA酶领域现存的挑战, 总结和展望了新思路和新方向.     

Stabilization of Linear C3 by Two Donor Ligands: A Theoretical Study of L-C3-L (L=PPh3, NHCMe,cAACMe)**

Quantum chemical studies using density functional theory and ab initio methods have been carried out for the molecules L-C₃-L with L=PPh₃ ( 1 ), NHC^Me ( 2 , NHC=N-heterocyclic carbene), and cAAC^Me ( 3 , cAAC=cyclic (alkyl)(amino) carbene). The calculations predict that 1 and 2 have equilibrium geometries where the ligands are bonded with rather acute bonding angles at the linear C₃ moiety. The phosphine adduct 1 has a synclinal (gauche) conformation whereas 2 exhibits a trans conformation of the ligands. In contrast, the compound 3 possesses a nearly linear arrangement of the carbene ligands at the C₃ fragment. The bond dissociation energies of the ligands have the order 1 < 2 < 3 . The bonding analysis using charge and energy decomposition methods suggests that 3 is best described as a cumulene with electron-sharing double bonds between neutral fragments (cAAC^Me)₂ and C₃ in the respective electronic quintet state yielding (cAAC^Me)=C₃=(cAAC^Me). In contrast, 1 and 2 possess electron-sharing and dative bonds between positively charged ligands [(PPh₃)₂]⁺ or [(NHC^Me)₂]⁺ and negatively charged [C₃]⁻ fragments in the respective doublet state.     

基于POE教学策略和比较思维的教学——以“碳酸钠和碳酸氢钠的性质”为例

以POE教学策略组织教学,尝试用比较思维方法学习碳酸钠、碳酸氢钠的性质,并设计多组实验比较碳酸钠、碳酸氢钠的结构、性质等,以期学生学会用比较思维和化学科学研究的一般步骤。     

New aspects of martensite stabilization in Ni–Mn–Ga high-temperature shape memory alloy

We report on new aspects of martensite stabilization in high-temperature shape memory alloys. We show that, due to the difference in activation energies among various structural defects, an incomplete stabilization of martensite can be realized. In material aged at high temperatures, this gives rise to a variety of unusual features which are found to occur in the martensitic transformation. Specifically, it is shown that both forward and reverse martensitic transformations in a Ni–Mn–Ga high-temperature shape memory alloy can occur in two steps. The observed abnormal behaviour is evidence that, in certain circumstances, thermoelastic martensitic transformation can be induced by diffusion.     

高精度全景补偿电子稳像

针对摄像机拍摄目标过程中自身的随机抖动造成的视频序列不稳定,以及稳像补偿过程中边缘信息的丢失,提出了基于SURF（Speed-up Robust Feature）算法的全景电子稳像方法。首先,运用SURF算法提取当前帧图像和参考帧图像的兴趣点,将两幅图像的兴趣点进行匹配,建立两帧的对应关系。针对兴趣点数目较少及场景中部分区域特征相似的情况,引入了兴趣点位移一致性抑制策略,改进了RANSAC（RANdom SAmple Consensus）误匹配的剔除算法,使得运动矢量的精确度小于1 pixel。然后,判定参考帧的更新策略,获取平滑的运动变量。最后,进行运动补偿,运用图像镶嵌技术对丢失的边缘区域信息进行全景补偿,得到了高精度的全景稳像结果,实验得到的输出视频峰值信噪比（PSNR）提高了33.1%。