Dynamic output feedback control for nonlinear networked control systems with a two-terminal event-triggered mechanism

Nonlinear Dynamics - This paper is mainly concerned with the stabilization problem for nonlinear networked control systems (NCSs) with a two-terminal event-triggered mechanism. Firstly,...     

1.3μm GaAs基量子点垂直腔面发射激光器结构设计与分析

结合垂直腔面发射激光器（VCSEL）原理以及量子点增益特点，计算了不同结构VCSEL的腔内损耗和量子点的模式增益.分析了激光器阈值特性以及氧化限制层对光损耗的影响.设计了含 氧化限制层的13μm量子点VCSEL结构. 关键词： 量子点 垂直腔面发射激光器 增益     

Studies of interfacial regions by sum-frequency generation with a free-electron laser

The use of a Free-Electron Laser (FEL) allows the study of (non)linear optical properties of materials over unsurpassed large spectral intervals. As an example, we report on the use of a FEL as the infrared source in spectroscopic infrared-visible Sum-Frequency Generation (SFG). Employing the extremely wide tunability of the Free-Electron Laser for Infrared eXperiments (FELIX) at Rijnhuizen, we have studied the frequency dependence of the nonlinear susceptibility for sumfrequency generation in gallium phosphide between 20 and 32 m in great detail. We have developed a shortpulse visible laser system that is highly synchronous with FELIX thereby creating a two-color setup that can be broadly applied. Resonantly enhanced SFG in alphaquartz has been used to study the relative timing stability of FELIX and the synchronized picosecond-laser system.Paper presented at the 129th WE-Hearaeus-Seminar on Surface studies by Nonlinear Laser Spectroscopies, Kassel, Germany, May 30 to June 1, 1994     

Mechanism of action of base-catalyzed oxygenation of phenol derivatives

Cyclopropyl derivative of 2,6-di-tert-butylphenol is synthesized as a probe to investigate the mechanism of base-catalyzed autooxidation of phenol derivatives. Our study indicates that one electron reduction of molecular oxygen from phenolate gives phenoxyl radical 3, a key intermediate of autooxidation. The coupling of phenoxyl radical and superoxide radical gives peroxylate anion 4 and produces the final epoxy alcohol adduct 6.     

Static secondary ion mass spectrometry for organic and inorganic molecular analysis in solids

The use of mass spectra in secondary ion mass spectrometry (S-SIMS) to characterise the molecular composition of inorganic and organic analytes at the surface of solid samples is investigated. Methodological aspects such as mass resolution, mass accuracy, precision and accuracy of isotope abundance measurements, influence of electron flooding and sample morphology are addressed to assess the possibilities and limitations that the methodology can offer to support the structural assignment of the detected ions. The in-sample and between-sample reproducibility of relative peak intensities under optimised conditions is within 10%, but experimental conditions and local hydration, oxidation or contamination can drastically affect the mass spectra. As a result, the use of fingerprinting for identification becomes compromised. Therefore, the preferred way of interpretation becomes the deductive structural approach, based on the use of the empirical desorption–ionisation model. This approach is shown to allow the molecular composition of inorganic and organic components at the surface of solids to be characterised. Examples of inorganic speciation and identification of organic additives with unknown composition in inorganic salt mixtures are given. The methodology is discussed in terms of foreseen developments with respect to the use of polyatomic primary ions.     

The use of high-performance liquid chromatography in the isolation and characterisation of mouse and rat epidermal growth factors and examination of apparent heterogeneity

Various epidermal growth factor preparations obtained from the mouse submaxillary gland (mEGF), have been separated into a number of components by reversed-phase high-performance liquid chromatography (HPLC). It is shown here, however, that when the mEGF is isolated rapidly, using only reversed-phase HPLC for trace enrichment and high-resolution fractionation, it is a single molecular species as determined with several ion-pairing solvent systems, provided that proteolysis is inhibited in the original extracts. This indicates that the minor components of mEGF that have been reported are artefacts formed during the isolation procedure, and are of no biological significance. The products of deliberate mild degradation of mEGF are shown to produce similar chromatographic profiles to those observed in samples of mEGF prepared in the absence of proteolytic inhibitors. Rat EGF has been isolated in a similar manner, and is shown to share many of the properties of the major tryptic digestion product of mEGF.     

Construction of a tethered poly(ethylene glycol) surface gradient for studies of cell adhesion kinetics

Surface gradients can be used to perform a wide range of functions and represent a novel experimental platform for combinatorial discovery and analysis. In this work, a gradient in the coverage of a surface-immobilized poly(ethylene glycol) (PEG) layer is constructed to interrogate cell adhesion on a solid surface. Variation of surface coverage is achieved by controlled transport of a reactive PEG precursor from a point source through a hydrated gel. Immobilization of PEG is achieved by covalent attachment of the PEG molecule via direct coupling chemistry to a cystamine self-assembled monolayer on gold. This represents a simple method for creating spatial gradients in surface chemistry that does not require special instrumentation or microfabrication procedures. The structure and spatial distribution of the PEG gradient are evaluated via ellipsometry and atomic force microscopy. A cell adhesion assay using bovine arteriole endothelium cells is used to study the influence of PEG thickness and chain density on biocompatibility. The kinetics of cell adhesion are quantified as a function of the thickness of the PEG layer. Results depict a surface in which the variation in layer thickness along the PEG gradient strongly modifies the biological response.     

多轴协调运动控制在某连续式风洞应用研究

为解决风洞试验过程中可靠地、精确地控制半柔壁系统型面变化,必须使电动推杆多轴协调同步运动;以某连续式风洞半柔壁系统为例,采用西门子T-CPU和S120伺服单元搭建硬件系统,运用梯形或S形加速与减速方式,保证同启同停进行同步,并将实际位置值实时与理论计算值进行比对,协调同步运动电动推杆,从而精确控制半柔壁系统型面变化;试验结果表明,该方法能够实现半柔壁机构在运动中多轴协调同步,保证机构运行安全;该系统在国内风洞半柔壁控制领域尚属首例,理论方法高效且通用性较强可广泛用于使用任何品牌和型号伺服控制系统控制半柔或全柔系统。     

A simple taste analyzing system design for visual and quantitative analysis of different tastes using multi-array chemical sensors and pattern recognition techniques

In this paper, we describe design of a simple taste analyzing system using sensory system based on a multi-array chemical sensor (MACS) and personal digital assistant (PDA) for visual and quantitative analysis of different tastes using pattern recognition techniques. The sensory system is communicated with PDA, which has several interesting benefits for data analysis and display, via wireless using the Bluetooth. A various pattern recognition techniques are adapted including spider map, principal component analysis (PCA) and fuzzy C-means (FCM) algorithm to classify visually data patterns detected by the sensory system. The proposed techniques can be determined the cluster centers and membership grade of patterns through the unsupervised way. The membership grade of an unknown pattern, which does not shown previously, can be visually and analytically determined. Throughout the experimental trails, the taste analyzing system is demonstrated robust performance through data acquisition via wireless communication and visual and quantitative analysis of different tastes for the liquids. The system, which is implemented as a simple hand-held taste analyzing instrument, can be applicable to on-site taste monitoring.     

Synthesis of functionalized organotrifluoroborates via the 1,3-dipolar cycloaddition of azides

[reaction: see text] We have successfully prepared potassium azidoalkyltrifluoroborates from the corresponding halogen compounds in 94-98% yields through a nucleophilic substitution reaction with NaN(3). In the presence of various alkynes and Cu(I) as a catalyst, these azidotrifluoroborates easily formed 1,4-disubstituted organo-[1,2,3]-triazol-1-yl-trifluoroborates in 85-98% yields. This method was then developed into a facile one-pot synthesis for the preparation of various organo-[1,2,3]-triazol-1-yl-trifluoroborates using haloalkyltrifluoroborates as the starting materials.