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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. 相似文献
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HU Bin-jie YUNG Kai-ning 《通信学报》2004,25(12):148-151
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. 相似文献
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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. 相似文献
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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. 相似文献
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Scanning Electron Microscopy and Transmission Electron Microscopy Study of Ferroelectric Domains in Doped BaTiO3 总被引:1,自引:1,他引:0
YUNG H. HU HELEN M. CHAN ZHANG XIAO WEN MARTIN P. HARMER 《Journal of the American Ceramic Society》1986,69(8):594-602
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. 相似文献
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KLAUS DIETER SCHWENKE BARBARA RAAB WILMA PHTZ DIETRICH ZIRWER KIM YUNG HAK 《Journal of Food Biochemistry》1989,13(5):321-334
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. 相似文献
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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 (Pb0.97La0.03)(Zr0.52Ti0.48)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. 相似文献
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