Showing papers by "University of Electronic Science and Technology of China published in 1996"

Global exponential stability and periodic solutions of delay Hopfield neural networks

Abstract: Both global exponential stability and periodic solutions of delay Hopfield neural networks are analysed via the method of constructing suitable Lyapunov functionals. Simple sufficient conditions are given for global exponential stability and the existence of periodic solutions. The conditions are presented in terms of the parameters of the connection matrix, and they are easy to check and apply in practice

Brief communication Periodic solutions and stability of Hopfield neural networks with variable delays

Abstract: Periodic solutions and global stability of Hopfield neural networks with variable delays are investigated. Sufficent conditions are given for the existence of periodic solutions and for the global stability

CFA based fully integrated Tow-Thomas biquad

Abstract: A fully integrated Tow-Thomas (TT) biquad is generated using CFA based integrators developed by the authors. The proposed circuit has the following features: use of only grounded capacitors, orthogonal voltage control of /spl omega//sub 0/, and Q, and cascadability. Simulation results which agree well with the theoretical analysis are obtained.

Comparison of Self‐Assembled Monolayers of n‐Alkanethiols and Phenylthioureas on the Surface of Gold

Abstract: Long-chain alkanethiols [R(CH 2 ) n SH] and substituted phenylthioureas (RPhNHCSNH 2 ) adsorb from solutions on the surface of gold. Analysis by XPS indicates that the binding energies of the S 2p and Au 4d 5 peaks in alkanethiol monolayers are 162.3 and 335.4 eV, which are 1.4 and 0.4 eV higher than those in phenyl-thiourea monolayers, respectively ; the widths (FWHM) of the S 2p XPS peaks in alkanethiols are less than those in phenylthioureas. The alkyl chain in alkanethiol monolayers on gold is canted 30° from the normal to the surface, while the longitudinal dimension of the phenylthiourea molecule is perpendicular to the surface. It is suggested that the covalent bond between sulphur and gold dominates the conversion of alkanethiols to gold alkane-thiolates, whereas the σ-π delocalized coordinate bond between sulphur and gold controls the adsorption of phenylthioureas on the surface of gold because of the existence of the conjugated π 4 6 bond in thioureas.

Electromagnetic instability in an ion-channel electron cyclotron maser

Abstract: A new plasma maser scheme, the ion-channel electron cyclotron maser (ICECM) is investigated, and the electromagnetic instability in the ICECM is studied. Using three-dimensional perturbation theory, the dispersion relation of the ICECM is derived in this paper. Analysis finds that three typical regions of electromagnetic instability exist in the ICECM after considering the influence of the plasma wave, and some potential physical mechanisms for the instability are identified. In the Compton regime, an approximate calculation example for the instability growth rate is given. As a high-power short-wavelength electromagnetic radiation source, some evident advantages of ICECM in comparison with other electron cyclotron masers are shown.

Green dyadics in reciprocal uniaxial bianisotropic media by cylindrical vector wave functions.

Abstract: The reciprocal uniaxial bianisotropic medium, which can be fabricated by polymer synthesis techniques, is a generalization of the well-studied chiral medium. It has potential applications in the design of antireflection coating, antenna radomes, and interesting microwave components. In the present investigation, based on the concept of spectral eigenwaves, eigenfunction expansion of the Green dyadics in this class of materials is formulated in terms of cylindrical vector wave functions. The formulations are greatly simplified by analytically evaluating the integrals with respect to the spectral longitudinal and radial wave numbers, respectively. The analysis indicates that the solutions of the source-incorporated Maxwell's equations for a homogeneous reciprocal uniaxial bianisotropic medium are composed of two eigenwaves traveling with different wave numbers, and each of these eigenwaves is a superposition of two transverse waves and a longitudinal wave. The Green dyadics of planarly and cylindrically multilayered structures consisting of the reciprocal uniaxial bianisotropic media can be straightforwardly obtained by applying the method of scattering superposition and appropriate electromagnetic boundary conditions, respectively. The resulting formulations, which can be theoretically verified by comparing their special forms with existing results, provide a fundamental basis to analyze and understand the physical phenomena of unbounded and multilayered reciprocal uniaxial bianisotropic media. The method employed here can be generalized to derive the eigenfunction expansion of Green dyadics in other kinds of media. \textcopyright{} 1996 The American Physical Society.

Theory of wave propagation along waveguide filled with plasma in finite magnetic field

Abstract: Rigorous analytical theory of wave propagation along a cylindrical waveguide filled with plasmas in a dielectric tube immersed in finite magnetic field is presented.The field components' expressions,eigenvalues,dispersion equations and complex wave power transmission equations have been obtained rigorously and discussed in detail.It is shown analytically that there is no disruption of the wave propagationin the ECR (ω=ωa) case,although the electrical permittivities approach to infinite in the case,and it hasbeen found that a real resonance takes place in this case while ω=(ωa2+ωpc2)1/2,in which the wave propagationof any mode is broken.The effective collisions are taken into consideration in the theory.Based on the above theory,the analytical theory of corrugated plasma waveguide immersed in finite axial magnetic field is also presented.The Floquet's expansion of field components,the dispersion equations,and the coupling coefficients of the corrugated plasma waveguide have been derived rigorously and discussed in detail.

A research on rheological properties of erythrocyte of lung cancer patients

Abstract: The erythrocyte deformability, the membrane lipid fluidity and the anion permeability of erythrocytes for lung cancer patients were measured and the results were compared with those of healthy persons. The experimental results showed that the blood viscosity of lung cancer patients increased, the erythro-cyte deformability of lung cancer patients decreased, the erythrocyte membrane lipid fluidity and membrane anion permeability of lung cancer patients decreased as well. INTRODUCTION The major function of blood is carrying oxygen and nourishment to tissues, sending out the waste of metabolism and maintaining the body in physiological balance. The function of oxygen transportation is influenced not only by the number of erythrocytes and the quality and quantity of hemoglobin, but also by the rheological properties of blood cells. Erythrocytes are the major component of blood and play an important role in blood rheological properties. That erythrocytes have good deformability is a favourable condition for erythrocytes to go through the capillary. The erythrocyte deformability is strongly influenced by the erythrocyte membrane mechanical properties, which are determined by the structural and functional properties of membrane protein and lipid (1,2, 3). In some disease, the changes of structure and function of mem brane protein and lipid may cause the change of erythrocyte deformability. Erythrocyte membrane lipid fluidity is one of the mechanical properties of erythrocyte membrane. It has a close relation with the membrane tank tread motion, deformability, oxygen diffusion and enzyme activity. The change of membrane lipid fluidity can reflect the change of the structure and function of membrane protein and lipid (4). The permeability is another important property of erythrocyte membrane. Depending on Key Words, Lung cancer, erythrocyte, deformability, lipid fluidity, anion permeability.

Characterization of self-assembled monolayers of thiols on Au(111)

Abstract: Self-assembled monolayers (SAMs) of n-butanethiol, n-dodecanethiol and their equimolar mixture on Au(111) were prepared and characterized by ellipsometry, contact angle measurement, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Results revealed that these SAMs are oriented ultrathin films with the thickness of nanometer scale, and the SAMs were influenced by the molecular chain length, the lattice orientation and cleanliness of the substrates. The surface of the longer chain SAM is hydrophobic. The thicknesses of three SAMs of n-butanethiol, n-dodecanethiol and their mixture revealed by ellipsometry and XPS are about 0.59 - 0.67nm, 1.60- 1.69 nm and 1.23 - 1.32nm, respectively. AFM images further demonstrated that the SAM formed by the mixture has some microdomains with two different thicknesses.

Fast interpolation of n-dimensional signal by subsequence FFT

Abstract: Based on the differential property of Fourier transform and the Taylor expansion of a n-variables function, the subsequence interpolating algorithm is extended to a general n-dimensional signal. As the interpolating process is consisted of a few parallel inverse FFT with the same size as the forward FFT, it is very efficient and is suitable for parallel processing.

Comparative study on the doping effect of 3d elements in Bi1.5Pb0.2Sr2Ca2Cu2.8M0.2O y (M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn)

Abstract: With XRD, R-T, and ac chi measurements a comparative study on the doping effects of 3d elements in Bi(1.5)Pb(0.2)Sr(2)Ca(2)Cu(2.8)M(0.2)O(y) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and on T-c, from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.

Imaging of EEG by spherical harmonic analysis

Abstract: A new three dimensional imaging method for electroencephalogram(EEG) is suggested. It consists of the solution of an inward spherical harmonic continuation. The principle of the new method is introduced in Section II, then a few numerical simulation tests are shown and the feasibility of the new method is confirmed by the simulation results.

A rigorous study of the rf fields in complex cavities with gradual transitions

Abstract: Based on mode coupling theory, the general form of coupled second order differential equations for the longitudinal rf standing-wave amplitudes in a complex cavity with gradual transition is developed. The TM type non-principal modes generated due to mode conversion are systematically taken into account. Comparisions of numerical results including or excluding TM modes are made for several examples and some interesting results are obtained.

Role of interfaces in deformation and fracture of ordered intermetallics

Abstract: While sub- and grain-boundaries are the primary dislocation sources in Ll{sub 2} alloys, yield and flow stresses are strongly influenced by the multiplication and exhaustion of mobile dislocations from the secondary sources. The concept of enhanced microplasticity at grain boundaries due to chemical disordering is well supported by theoretical modeling, but no conclusive direct evidence exist for Ni{sub 3}Al bicrystals. The strong plastic anisotropy reported in TiAl PST (polysynthetically twinned) crystals is attributed in part to localized slip along lamellar interfaces, thus lowering the yield stress for soft orientations. Calculations of work of adhesion suggest that, intrinsically, interfacial cracking is more likely to initiate on {gamma}/{gamma}-type interfaces than on the {alpha}{sub 2}/{gamma} boundary. 70 refs, 5 tabs, 5 figs.

Studies on new YAG phosphor screen for HDTV projector

Abstract: The paper makes a systematic exposition of the theory and technology of a new kind of yttrium aluminum oxide garnet (YAG) phosphor screen (2 approximately 3 inches diagonal)-- the heart of a large screen (greater than 72 inches diagonal) HDTV projector with high brightness, high resolution and good contrast ratio. According to YAG's characteristics of high heat conductivity and high hardness and strength, we propose creatively the idea: fabricating YAG phosphor screen by depositing phosphor powder on YAG film. The YAG phosphor screen' capability of conducting heat is ten times greater than the conventional CRT phosphor screen, with the help of liquid cooling, the YAG phosphor screen avoids to some extent the phosphor's saturation and degradation by high density electron bombardment existing seriously in conventional CRT projector phosphor screen, so the YAG phosphor screen obtains very high brightness and good contrast ratio. Owing to the very small thickness, big refractive index of YAG film and the high density phosphor layer prepared by improved sedimentation and centrifugal sedimentation technics, the resolution of the YAG phosphor screen is high.

Time domain transmission properties of multi-vias

Abstract: The time domain transmission properties of multi-vias in MCM-C and MCM-D packages are investigated by the FDTD method. The results demonstrate that the crosstalk between two vias is negligible when their distance is larger than their width and excellent transmission properties can be achieved below 10GHz.

Analysis for the double staggered ladder circuit

Abstract: A new type of mm-wave slow wave system, double staggered ladder circuit is analyzed in this paper, by means of “average cavity field method” and three-dimensional finite element method. The influence of the electron beam channel on the dispersion characteristics is discussed. An experimental research is made, the experimental results agree well with the theoretical one.

Analysis of the leaky bucket algorithm for priority services

Abstract: The leaky bucket algorithm with loss priorities is studied in this paper. The analytical expression of the relation among leaky bucket performance, statistical parameters of input traffic and leaky bucket parameters for various priority services is obtained, and the effect of adjustment factor on leaky bucket performance of higher-priority service and lower-priority service is studied with two priority classes.

Performance analysis of leaky bucket algorithm with bursty traffic input in ATM networks

Abstract: A bursty traffic model is introduced in this paper to describe the statistical characteristics of packet video. The performance of leady bucket algorithm with bursty traffic input is analyzed. The influences of various parameters on QOS (Quality of Service) are investigated. The analysis shows that although the loss probability decreases through expanding the buffer capacity, the delay and delay jitter increase, whose effect on QOS will not be negligible.

A new type of quasi-optical cavity in millimeter wave-band

Abstract: A new type of cavity-the resonator of plane mirrors with dielectric tubes is analyzed theoretically and experimentally. Making use of equivalent dielectric constant method, we calculated the field distribute, quality factor, attenuate and transmission constant in the cavity. We measured the parameter of the cavity and discovered that the cavity's quality factor is high, band-width wide, modes less and structure simple.

Study of sectorial groove—gap RF structure for cusptron

Abstract: A novel sectorial groove-gap RF structure for cusptron (gyromagnetron) is presented and its characteristic equation and stored energy expression are derived. The magnetron-like vane structure is a special case of this structure. The calculated curves of dispersion, energy and efficiency are given and the results show that maximum efficiency η=16.1% is obtained when the sectorial groove-gap is evolved to vane structure.