Showing papers by "University of Electronic Science and Technology of China published in 1997"
TL;DR: Under some mild conditions on the repair time and service time distributions, some reliability problems of the single-server M/G/1 queueing system are studied, and some satisfactory results are obtained.
93 citations
TL;DR: In this paper, a numerical study of direct TM/sub 01/-TE/sub 11/ mode converters in highly overmoded, bent smooth, circular waveguides is presented for high-power millimeter waves.
Abstract: In this paper, a numerical study of direct TM/sub 01/-TE/sub 11/ mode converters in highly overmoded, bent smooth, circular waveguides is presented for high-power millimeter waves. The various shapes of bent waveguides are elaborately chosen, and their optimized geometrical dimensions have been achieved with a general optimization code employing the coupled mode theory. The mode converters designed can have high conversion efficiencies over 98% and wide bandwidths of 28%.
56 citations
TL;DR: In this article, the angular transmission of PDLC films has been experimentally investigated as a function of droplets dimension, refractive indices and thickness of sample, and the experimental data have been interpreted in terms of the Anomalous Diffraction Approximation slightly modified in order to take into account extra-scattering phenomena generated by some of the peculiar PDLC characters.
Abstract: The angular transmission of Polymer Dispersed Liquid Crystals (PDLC) films has been experimentally investigated as a function of droplets dimension, refractive indices and thickness of sample. The experimental data have been interpreted in terms of the Anomalous Diffraction Approximation slightly modified in order to take into account extra-scattering phenomena generated by some of the peculiar PDLC characters. The dimension of the droplets and refractive index difference between polymer and liquid crystal are found to be the most important factors affecting the light transmission as well as extra scattering factors.
35 citations
TL;DR: In this paper, the authors proposed a method to improve the quality of the data collected by the data collection system of the Internet.Abstracts are not published in this journal. But
Abstract: Abstracts are not published in this journal
18 citations
TL;DR: In this paper, an internal polarization field was measured by observing the electrooptical response of a PDLC film under a low frequency driving voltage, which corresponded to the D.C. bias voltage needed to equalize the light transmission in the two half periods.
Abstract: A memory state can be induced in PDLC films through the application of a strong D.C. voltage. This memory state is due to the onset of an internal polarization field, which keeps the film in a high transparent state. This polarhation field remains in the film from hours to weeks, depending on the temperature at which the external polarizing field is applied. We have found the way to measure such an internal field by observing the electrooptical response of the film, under a low frequency driving voltage. Due to the presence of the polarization field the light transmission obtained during the positive half period of the driving voltage is not equal to that observed in the negative half period. The polarization field corresponds to the D.C. bias voltage which is needed to equalize the light transmission in the two half periods. The time dependence of the polarization field has been determined.
16 citations
TL;DR: In this article, the relationship between mass attenuation coefficients and incoherent scattering radiation is not an inverse proportion but a power function over a wide range of atomic numbers (e.g. 5B-40Zr and H3BO3-KBr).
Abstract: It is shown that the relationship between mass attenuation coefficients and incoherent scattering radiation is not an inverse proportion but a power function over a wide range of atomic numbers (e.g. 5B–40Zr and H3BO3–KBr). The experimental results are in good agreement with this theoretical prediction. A new method is recommended for matrix absorption correction in x-ray fluorescence analysis using the power function of Rh Kα Compton peak intensity. The method has been experimentally proved to be correct and superior to the traditional scattering internal standard technique over a wide range of matrix compositions, partially in application to trace element determinations in heavy matrix absorption samples. © 1997 by John Wiley & Sons, Ltd.
11 citations
TL;DR: In this paper, the authors formulated the Green dyadics of planarly and cylindrically multilayered structures consisting of uniaxial bianisotropic-ferrite media by applying the method of scattering superposition and appropriate electromagnetic boundary conditions respectively.
Abstract: The uniaxial bianisotropic-ferrite 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 novel 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 the cylindrical vector wavefunctions. The formulations are greatly simplified by analytically evaluating the integrals with respect to the spectral longitudinal and radial wavenumbers, respectively. The analysis indicates that the solutions of the source-incorporated Maxwell's equations for a homogeneous uniaxial bianisotropic-ferrite medium are composed of two (or four) eigenwaves travelling with different wavenumbers. 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 uniaxial bianisotropic-ferrite 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 fundamental basis to analyse the physical phenomena of unbounded and multilayered uniaxial bianisotropic-ferrite media.
10 citations
TL;DR: In this paper, a new method of S-parameter extraction from the FDTD in analyses of microstrip circuits is proposed, which only uses the Ex-field component parts in three selected transverse cross sections of the transmission line under approach.
Abstract: A new method of S-parameter extraction from the FDTD in analyses of microstrip circuits is proposed. It only uses the Ex-field component parts in three selected transverse cross sections of the transmission line under approach. The reflection coefficient is extracted from a single run of the FDTD. Neither prior knowledge of the line nor any computation of the derivative of the electric and magnetic fields is needed. The proposed new method is directly applicable to analyses of the discontinuities of microwave transmission circuits. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 162–163, 1997.
7 citations
TL;DR: In this article, the transient solutions for M/G/1 queues with single server vacation and multiple server vacations are firstly studied, and the recursion expressions of their Laplace transform are given.
7 citations
TL;DR: In this paper, the small signal gain of the relativistic traveling wave tube is analyzed and some conclusions are drawn, and the analysis method presented in this paper can be extended to other types of slow wave structures of the wave tube.
Abstract: The relativistic traveling wave tube is an important high power microwave source. The corrugated cylindrical waveguide is usually used as slow wave structure of this device. Starting from wave equation and using boundary conditions, dispersion relation is derived for the corrugated waveguide, in which an intense relativistic electron beam propagates along the axis. Two cases which are shorter period and longer period are discussed in this paper respectively. The small signal gain of the relativistic traveling wave tube is analyzed and some conclusions are drawn. The analysis method presented in this paper can be extended to other types of slow wave structures of relativistic traveling wave tube.
7 citations
TL;DR: In this article, a general group of formulas by a combination of conformal mapping and 2-D FDTD (CF-FDTD) is presented, and a comparison of numerical results is presented.
Abstract: This paper presents a general group of formulas by a combination of conformal mapping and 2-D FDTD (CF–FDTD). By this new method, the cutoff wavenumbers and dispersive characteristics of higher order TE modes in an eccentric coaxial line are given. A comparison of numerical results is presented. © 1997 John Wiley & Sons, Inc. Microwave Opt Technol Lett 16: 249–252, 1997.
TL;DR: In this article, a numerical method based on the coupling of the finite difference method in time domain with the discrete Fourier transform is applied to calculate the eigenfrequencies and eigenfield distribution of a resonant cavity which is an appropriately shorted periodic slow wave circuit of N periods at both ends.
Abstract: A novel, highly accurate numerical synthetic technique for determining the complete dispersive characteristics of electromagnetic modes in a spatially periodic structure is presented. The numerical method based on the coupling of the finite difference method in time domain with the discrete fourier transform is applied to calculate the eigenfrequencies and eigenfield distribution of a resonant cavity which is an appropriately shorted periodic slow wave circuit of N periods at both ends. The analytical synthetic technique, which is based on the intrinsic characteristic of spatially periodic structure, is used to derive the complete dispersion relation using the numerically measured resonances. The method was successfully applied for the case of TMon modes in a coaxial corrugated waveguide and is applicable to slow wave structures of arbitrary geometry.
TL;DR: In this paper, the surface modes in the plasma circular cylindrical waveguide in a lossy material are analyzed, particularly for the variations of their propagation properties with plasma parameters and surrounding material.
Abstract: The surface modes in the plasma circular cylindrical waveguide in a lossy material are analyzed, particularly for the variations of their propagation properties with plasma parameters and surrounding material. The characteristic equations of surface modes are derived, and their relevant approximate solutions are given. The limit results of this paper are consistent with that given in literature’s. The analysis show that it can be used to improve the properties of mode suppressors and fabricat cut-off attenuators.
TL;DR: This paper defines increasing (decreasing) L -fuzzy syntopogenous spaces with preorder and study some properties of them and investigates their corresponding structures and their properties.
TL;DR: In this article, the structure of cylindrical cavity coupling with rectangular waveguides through large apertures on the cavity sidewall is studied in detail, and the fields in the cavity are properly expanded by derived mode functions.
Abstract: The structure of cylindrical cavity coupling with rectangular waveguides through large apertures on the cavity’s sidewall is studied in detail. The fields in the cavity is properly expanded by derived mode functions. By making reasonable approximation of the boundary conditions, the process of derivation and the formation of the characteristic equation is greatly simplified. The characteristic equation and model coefficients are obtained. The reliability of the derived characteristic equation is tested. Numerical results of characteristic frequency and quality factor changing with dimensions of coupling holes are given.
TL;DR: The fundamental model resonant wavelength of a composite microstrip antenna is analyzed with Rayleigh-Rits method, the numberial examples are compared with experimental results, the measured data verify the theoretical values.
Abstract: The fundamental model resonant wavelength of a composite microstrip antenna is analyzed with Rayleigh-Rits method, the numberial examples are compared with experimental results, the measured data verify the theoretical values.
TL;DR: In this paper, a slow wave structure named Π-line is analyzed and the dispersion relations of both symmetrical and antisymmetrical modes are derived by means of the field matching method.
Abstract: A slow wave structure named Π — line is analysed in this paper. This circuit propagates slow waves in symmetrical and antisymmetrical mode. The dispersion relations of both symmetrical and antisymmetrical modes are derived here, by means of the field matching method. Numerical results are also given in this paper. The Π — line slow wave structure is of large diameter, and its radial supported stubs provide good heat conduction paths. These properties make this circuit well suited for use in high power, millimeter wave traveling wave tubes.
TL;DR: In this paper, the variation of superconductive properties of GdBaCuO(GBCO) compound with the substrate temperature and sputtering pressure has been investigated, and the results are very useful to further prepare large area thin films of GBCO.
Abstract: Thin films of GdBaCuO(GBCO) compound have been deposited in situ onto LaAlO3 single crystal substrates by inverted cylindrical sputtering.The variation of superconductive properties of the thin films with the substrate temperature and sputtering pressure has been systematic investigated.By the optimization of deposition parameter,high quality c-axis epitaxial GBCO thin films of Tc0>92K were reproducibly grown at the substrate temperature of 720—820℃ with a low deposition total pressure (40Pa).The Tc0 of the best sample is as high as 93.2K.Only by changing the target composition into GdBa2Cu4Oy (Gd124),was it observed that the samples always contain some a-axis oriented films,impling that excess copper would favour a-axis growth in thin films,and the Tc of the samples is lower than that with Gd123 target.The superconductivity of the thin films under high substrate temperature was clearly improved by the procedure of special post oxygenization at 400℃ in ozone atmosphere.These results are very useful to further prepare large area thin films of GBCO.
TL;DR: In this paper, a new type of circular-shaped microshield and conductor-backed coplanar waveguide is proposed, and analytical closed-form expressions for characteristic impedance and effective dielectric constant for the new line are obtained using conformal mapping method under the assumption of pure-TEM propagation and zero dispersion.
Abstract: In this paper, a new type of circular-shaped microshield and conductor-backed coplanar waveguide is proposed. Analytic closed-form expressions for characteristic impedance and effective dielectric constant for the new line are obtained using conformal mapping method under the assumption of pure-TEM propagation and zero dispersion. The new waveguide proposed by this paper can reduce radiation to much less than the conventional coplanar waveguide and microstrip, and can reduce the current concentration at both the edges of the strip conductor.
TL;DR: In this paper, the numerical solution of Green's function for the potential in 2D arbitrary inhomogeneous media with axial symmetry has been given by use of efficient half-analytical, half-numerical hybrid method.
Abstract: The numerical solution of Green’s function for the potential in 2-D arbitrary inhomogeneous media with axial symmetry has been given by use of efficient half-analytical, halfnumerical hybrid method Then the logging responses of various kinds of the DC resistivity log with axisymmetric excitation have been obtained by using surface integral equation method to match the boundary conditions on the electrodes of the logging sonde Comparing the results with that obtained by other methods, one can see good precision and efficiency of the given method Some applications of the numerical modeling have been also discussed
TL;DR: In this article, the S parameters of multi-vias in multi-chip Module(MCM) package are extracted by the Finite Difference Time Domain (FDTD) method combined with the Fourier transform and theory of network.
Abstract: TheS parameters of multi-vias in Multi-Chip Module(MCM) package are extracted by the Finite Difference Time Domain(FDTD) method combined with the Fourier transform and theory of network. The results demonstrate that excellent transmission properties are available at least below10GHz in Ceramic MCM(MCM-C) package and30GHz in Deposited MCM(MCM-D) package, and the transmission properties are not sensitive to the given distance between two proximate vias.
TL;DR: In this article, the significance of two new types organic electronic crystals based on substituted phenylthiourea and N-phenylphthalic imidine have been illustrated, and the synthesis preparation, molecular structure, dielectric and piezoelectric properties were discussed.
Abstract: The significance of two new types organic electronic crystals based on substituted phenylthiourea and N-phenylphthalic imidine have been illustrated in this paper. Five crystal materials: p-methylphenylthiourea (I, C8H10 N2S), p-chlorophenylthiourea (I, C7H7ClN2S), 2, 4, 6-tribromophenylthiourea (I, C7H5Br3N2S), N-(phenyl) phthalic imidine (IV, C14 H9NO2) and N-(p-methylphenyl) phthalic imidine (V, C15H11NO2) were prepared and confirmed by IR,NMR,MS and elementary analysis. The crystal and molecular structures were determined by X-ray diffraction. The relative dielectric constants er, piezoelectric parameters d33 and refractive index n were measured respectively. The synthesis preparation, molecular structure, dielectric and piezoelectric and optic properties were discussed.
24 Apr 1997
TL;DR: This successful experiment results indicates that the question that the traditional tracking method of quad detector is vain to the extended target has been overcome and testifies that the theory of the staring edge tracking is correct.
Abstract: The extended target that the size is larger that the diameter of the light beam can be tracked in the laser tracking radar designed on the basic of the method and the algorithm of the staring edge tracking A moving aluminium plate is tracked by a coherent CO2 laser tracking radar facility with transmitter power 5W and the divergent angle of the transmitter light beam less than 018 mrad at a n approximate range of 1 km The error signals of the azimuth and the elevation are generated from the quad detector This successful experiment results indicates that the question that the traditional tracking method of quad detector is vain to the extended target has been overcome and testifies that our theory of the staring edge tracking is correct This tracking method has many advantages For example, is we choose the tracking position at the top of the target, then the ground target is not easy to lose So it can avoid tracking the ground On the other hand, the range of the laser radar using this method is longer than the range of the radar using the point tracking, because the target using narrow light beam illumination is taken as an extended Lambertian target© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering Downloading of the abstract is permitted for personal use only
01 Jan 1997
TL;DR: A test pattern generation approach for digital circuit that can generate tests for all detectable faults including multi faults, possess the characteristics of parallel processing and can be implemented on multiprocessors.
Abstract: A test pattern generation approach for digital circuit is presented. The approach employs genetic algorithm to generate tests for faults. The gate level description of circuit under test (CUT) is translated into a nonlinear netwrok that can be computed easily,and an improved genetic algorithm is used to find out optimal solutions of energy function of the constrained network,so the test set of CUT is obtained. The approach has many merits,such as it can generate tests for all detectable faults including multi faults,possess the characteristics of parallel processing and can be implemented on multiprocessors.
TL;DR: Based on the calculation of photon absorption coefficient alpha and width W of the depletion region of mercury cadmium telluride detectors, the equation for alpha, W and the effective Franz-Keldysh shift Dlambda(ce) is derived.
Abstract: Based on the calculation of photon absorption coefficient alpha and width W of the depletion region of mercury cadmium telluride detectors, we derived the equation for alpha, W and the effective Franz-Keldysh shift Dlambda(ce). An interpretation of the substantial difference between Dlambda(ce) and the maximum Franz-Keldysh shift Dlambda(cm) of the cutoff wavelength is presented. We also propose a method to increase the Dlambda(ce) of mercury cadmium telluride detectors.
TL;DR: In this paper, the dispersion relation for the interaction between the electron beam and the symmetrical mode propagating in a slow wave circuit is obtained, by means of the Variational method.
Abstract: The ridge loaded ring-plane traveling wave tube can provide high output power in a relatively broader bandwidth. The dispersion relation for the interaction between the electron beam and the symmetrical mode propagating in this slow wave circuit is obtained, by means of the Variational method. The method to calculate the arbitrary order Bessel function with complex argument is discussed. The three dimensional trajectory graph of the Bessel function with complex argument is plotted. The instantaneous operating bandwidth can be estimated in terms of the relation between of the gain and frequency.
TL;DR: In this article, a cylindrical cavity filled with plasma, where the microwave comes from a vacuum cylinrical waveguide, was analyzed and the results showed that the curves of ion and electron density distributions are similar as the curve of electric field intensity distribution, and a critical electron density is exist.
Abstract: From the fluid model, the plasma is an isotropic medium. First, it is obtained that the microwave field in a cylindrical cavity filled with plasma, where the microwave comes from vacuum cylindrical waveguide. Coupling with fluid equations for the electron and ion motion, the microwave discharge courses are calculated. The results show that the curves of ion and electron density distributions are similar as the curves of electric field intensity distribution. Also, a critical electron density is exist. Above this density, microwave field will damp rapidly, this makes the gas ionization mainly happening on the surface.
TL;DR: A measurement system for accurate characterization of microwave surface resistance of high-T c superconductors (HTSC) thin films is presented in this article, where a special high Q-factor sapphire resonator probe with TE 011+δ mode was fabricated to measure the surface resistance R s of a single piece of HTSC thin film at 17 GHz and 77 K.
Abstract: A measurement system for accurate characterization of microwave surface resistance of high-T c superconductors (HTSC) thin films is presented. In this system a special high Q-factor sapphire resonator probe with TE 011+δ mode was fabricated to measure the surface resistance R s of a single piece of HTSC thin film at 17 GHz and 77 K. The system has a sensitivity about 100 μ Ω for HTSC samples under test with dimensions equal to or greater than Φ10 mm.