Reduced-order modelling of linear discrete-time systems via continued-fraction expansion of a z transfer function about z = 1 and z = a alternately

A new time-domain procedure is suggested for obtaining reduced-order models of linear time-invariant discrete-time systems. The procedure is based on presenting a new form of continued-fraction expansion (CFE) about z = 1 and z = a alternately, and deriving a realization form for the CFE. An algorithm is presented for obtaining the new CFE of the z transfer function of a linear discrete-time system from its state-space model directly, without having to determine the corresponding rational z transfer function. Also presented is a systematic approach to deriving two similarity transformation matrices: one is used to transform a state-space model from a general form to the CFE canonical form, and the other is used to transform a state-space model from the phase-variable canonical form to the CFE canonical form. Finally, an approximate aggregation matrix is constructed to relate the state vector of the original system to that of a reduced model obtained by the present method. The proposed procedure is illustrated with examples.     

Scattering performance of a plane wave by conducting finite helix

The scattering of a plane wave with a linear polarization by a conducting finite helix is presented. The analytical expresses of scattering field are obtained based on the boundary condition of a sheath helix model. Effects of a pitch angle and electrical size of the helix on the resonant behavior are investigated. The analysis shows that resonant behavior of the forward/backward scattering far field is only depended on the pitch electrical size and the radial electrical size, but it is independent of the turn of the helix.     

芦荟中药复合保健饮料的研制

芦荟中药复合保健饮料以芦荟为原料，以党参和麦冬为辅料，经科学方法配制而成。它含有芦荟素、麦冬及党参多糖等几十种具有调节新陈代谢，增强免疫力，消炎杀菌，降低血脂、血糖、和血压等作用；还有清心除烦、生津止渴的功效。产品符合卫生标准，是一种新型饮料，适于高血压，糖尿病及便秘等患者饮用。     

Cauer continued-fraction expansion about s = 0 and s = a for biased reduced-order state-space models

A method of linear-system reduction is presented which produces biased state-space models such that combinations of retained time-moments and weighted time-moments may be varied. The method is based on the concept of representing the system transfer function in a biased Cauer form of continued-fraction expansion (CFE) about s = 0 and s = a. A new algorithm for obtaining the continued-fraction expansion of the transfer function of a linear time-invariant system from its state-space model directly, without first determining the corresponding transfer function, is derived. A realization which uses only integrators for the biased Cauer continued-fraction expansion about s = 0 and s = a is presented. The corresponding canonical state-space model is established, which allows the reduced-order state-space model to be formed by directly partitioning the system matrices. Also presented are two new similarity transformation matrices; one is used to transform a state-space model from a general form to a state-space model in the biased CFE canonical form, and the other is used to transform a state-space model from phase-variable canonical form to the biased CFE canonical form.     

两强竞争市场中的企业广告策略分析

将Dawid和Feichtinger的混沌型的广告扩散型扩展到两强竞争的市场环境下，为检验模型的可用性开发了一个计算机仿真系统，仿真的结果表明在两强竞争下的企业最好的广告策略是增加广告投入直到达到“双赢状态”，即市场占有率的振荡即将发生的临界状态，分析应用结果表明提出的混沌型模型和开发的仿真系统为市场竞争环境下的企业广告策略的分析和制定提供了一个有效的工具。     

TRANSIENT ANALYSIS OF n-TIER GaAs MESFET MATRIX AMPLIFIERS BY THE TLM METHOD

The performances of n-tier GaAs MESFET matrix amplifiers are studied in the time domain. The model is developed incorporating the parasitic resistive loss and internal coupling capacitance of the active device. Techniques are contemplated to transform the matrix amplifier into a set of coupled multi-conductor transmission lines. The resultant model is analysed by the TLM method. Impulse responses of 2 × 4 and 3 × 3 matrix amplifiers are investigated. The frequency responses of the amplifiers are obtained through a Fourier transform. Agreement is observed between results obtained by the TLM model and those obtained by other analytical methods or a complicated circuit analysis program. A 5 × 7 matrix amplifier is also analysed to show the advantage of the developed method.     

Scanning Electron Microscopy and Transmission Electron Microscopy Study of Ferroelectric Domains in Doped BaTiO3

This paper describes the results of detailed studies carried out on Ca-doped and Nb-doped BaTiO₃ using scanning electron microscopy and transmission electron microscopy. The techniques used were topographical contrast, selected-area diffraction, and microdiffraction Kikuchi pattern analysis. By these methods it was possible to unambiguously identify the different types of domain boundaries. Also, evidence was obtained for the existence of an unconventional 90% domain boundary which has not previously been reported.     

MODIFICATION OF THE LOW-MOLECULAR WEIGHT BASIC ALBUMIN FRACTION FROM RAPESEED (BRASSICA NAPUS L.) BY ACETYLATION PART 1. CHEMICAL AND PHYSICOCHEMICAL ASPECTS1

The chemical and physicochemical changes of the low-molecular weight basic albumin fraction from rapeseed, as a function of degree of acetylation, were studied using amino and ester groups analyses, PAGE electrophoresis, isoelectric focusing, viscometry, circular dichroism and fluorescence spectroscopy. The surface hydrophobicity was evaluated by means of the ANS fluorescence probe technique. The protein was readily acetylated at the amino groups by addition of acetic anhydride. Acetylation of amino acid hydroxyl groups was significantly slower and proceeded in the presence of an excess of the reagent after the amino groups had already been blocked. Acetylation resulted in protein species with isoelectric points at pH 7.6, 6.6, 5.95 and 5.4. The intrinsic viscosity of the native protein fraction dropped from 0.159 dlg^?1 to 0.038 dlg^?1 at a moderate degree of modification. The secondary structure of the protein, characterized by a content of 40–45% helix conformation, was not significantly influenced by acetylation. Modification did not result in wavelength shifts of the peaks in the near ultraviolet CD and fluorescence spectra. However, the negative ellipticities in the 250–270 nm region of the CD spectrum increased markedly with increasing degree of acetylation. The surface hydrophobicity increased linearly with the amount of acetyl groups introduced into the protein.     

PHOTO INDUCED CURRENT IN (Pb0.97La0.03) (Zr0.52Ti0.48)O3 THIN FILMS OF DIFFERENT THICKNESSES

ABSTRACT

Photovoltaic effect in ferroelectric materials exhibits potential for applications of sensors and remote controls in micro-electro-mechanical systems, and a systematic evaluation on the photovoltaic behavior in ferroelectric materials becomes important. However, as a critical parameter that determines the photovoltaic output in ferroelectric thin films, the film thickness effect on photocurrent output has not been investigated for thin film samples. In this work, a theoretical model has been developed to describe the thickness-dependent photocurrent in (Pb_0.97La_0.03)(Zr_0.52Ti_0.48)O₃(PLZT) thin films with a sandwich electrode structure. This model indicates that photocurrent increases exponentially with the decrease in film thickness. Therefore, a significantly enhanced photocurrent can be expected in thinner PLZT films. The predicted thickness dependence of the short circuit photocurrent was also supported by our experimental results.     

发芽糙米的生理活性化工艺研究与控制

以糙米为主要原料，设计了糙米发芽的工艺流程，试验确定了生理活性化工艺过程的基本参数，开发了先进的控制系统，使糙米中富集了γ-氨基丁酸(GABA)，其含量大于650mg／100g，而且具有良好的适口性，为发芽糙米的工业化生产提供了依据。