Showing papers by "University of Electronic Science and Technology of China published in 2002"
TL;DR: In this paper, the response time of pure polyaniline (PAN) and polystyrenesulfonic acid (PSSA) composite films with various number of layers was investigated.
Abstract: Pure polyaniline (PAN) film, polyaniline and acetic acid (AA) mixed film, as well as PAN and polystyrenesulfonic acid (PSSA) composite film with various number of layers were prepared by Langmuir–Blodgett (LB) and self-assembly (SA) techniques. These ultra-thin films were characterized by ultraviolet–visible (UV–VIS) spectroscopy and ellipsometry. It is found that the thickness of PAN-based ultra-thin films increases linearly with the increase of the number of film layers. The gas-sensitivity of these ultra-thin films with various layers to NO 2 was studied. It is found that pure polyaniline films prepared by LB technique had good sensitivity to NO 2 , while SA films exhibited faster recovery property. The response time to NO 2 and the relative change of resistance of ultra-thin films increased with the increase of the number of film layers. The response time of three-layer PAN film prepared by LB technique to 20 ppm NO 2 was about 10 s, two-layer SA film was about 8 s. The mechanism of sensitivity to NO 2 of PAN-based ultra-thin films was also discussed.
226 citations
01 Jan 2002
TL;DR: In this paper, the Cauchy problem for the Euler equations for compressible fluids is reviewed, and the local and global well-posedness for smooth solutions is presented.
Abstract: Some recent developments in the study of the Cauchy problem for the Euler equations for compressible fluids are reviewed. The local and global well-posedness for smooth solutions is presented, and the formation of singularity is exhibited; then the local and global well- posedness for discontinuous solutions, including the BV theory and the L∞ theory, is extensively discussed. Some recent developments in the study of the Euler equations with source terms are also reviewed.
101 citations
TL;DR: By combining a number of different Lyapunov functionals with the Razumikhin technique, some sufficient conditions for the existence of a unique equilibrium and global asymptotic stability of the network are derived.
Abstract: In this paper, the bidirectional associative memory (BAM) neural network with axonal signal transmission delay is considered. This model is also referred to as a delayed dynamic BAM model. By combining a number of different Lyapunov functionals with the Razumikhin technique, some sufficient conditions for the existence of a unique equilibrium and global asymptotic stability of the network are derived. These results are fairly general and can be easily verified. Besides, the approach for the analysis allows one to consider several different types of activation functions, including piecewise linear sigmoids with bounded activations as well as C1-smooth sigmoids. It is believed that these results are significant and convenient in the design and applications of BAM neural networks. Copyright © 2002 John Wiley & Sons, Ltd.
76 citations
TL;DR: A method for estimating the three-dimensional distribution of equivalent current sources inside the brain from scalp potentials is developed and it is suggested that it may become an alternative approach to imaging spatially distributed current sources-sinks in the brain and other organ systems.
Abstract: We have developed a method for estimating the three-dimensional distribution of equivalent current sources inside the brain from scalp potentials. Laplacian weighted minimum norm algorithm has been used in the present study to estimate the inverse solutions. A three-concentric-sphere inhomogeneous head model was used to represent the head volume conductor. A closed-form solution of the electrical potential over the scalp and inside the brain due to a point current source was developed for the three-concentric-sphere inhomogeneous head model. Computer simulation studies were conducted to validate the proposed equivalent current source imaging. Assuming source configurations as either multiple dipoles or point current sources/sinks, in computer simulations we used our method to reconstruct these sources, and compared with the equivalent dipole source imaging. Human experimental studies were also conducted and the equivalent current source imaging was performed on the visual evoked potential data. These results highlight the advantages of the equivalent current source imaging and suggest that it may become an alternative approach to imaging spatially distributed current sources-sinks in the brain and other organ systems.
58 citations
TL;DR: In this paper, the stability of cellular neural networks with continuous time delay is investigated and a main theorem together with a few corollaries related to the existence and boundedness of the solution for this kind of CNNs, as well as its global asymptotic stability is derived.
52 citations
TL;DR: Numerical calculations show that there are many interesting and important features of the wave propagation along an MMPW compared with that in a stationary magnetized plasma-filled waveguide (MPW).
Abstract: Making use of the transformation of constitutive relations for electromagnetic waves and the transformation of the wave vector in Minkowski space, we have worked out the theory of wave propagation along a waveguide filled with moving magnetized plasma (MMPW). The dispersion equations of the wave propagation in a circular MMPW are given in this paper, along with a detailed discussion of their behaviors. Numerical calculations show that there are many interesting and important features of the wave propagation along an MMPW compared with that in a stationary magnetized plasma-filled waveguide (MPW).
31 citations
TL;DR: The new RBF based approach to LM provides an additional efficient way for the neural electrical activities imaging and is better than the SSF based method.
29 citations
TL;DR: In this paper, the existence of compact kernel sections for the process generated by a non-autonomous strongly damped wave equation with homogeneous Dirichlet boundary condition was proved. But the upper bound of the Hausdorff dimension of sections decreases as the damping grows for large strong damping.
26 citations
29 Jun 2002
TL;DR: A new access method that can be used in a post 3G mobile system is proposed and with this method, the system resources utilization can be optimized.
Abstract: A new access method that can be used in a post 3G mobile system is proposed In the future mobile communication systems, OFDM technology probably become the main technology On account of multi-traffic demands in the future, we should design the access method in OFDM system to accord with those demands With this method, the system resources utilization can be optimized
20 citations
TL;DR: The theoretical relation between the scalp Laplacian (SL) and the scalp current density (SCD) is derived for a spherical shell head model and shows that they are related by a function of spatial frequency.
Abstract: The theoretical relation between the scalp Laplacian (SL) and the scalp current density (SCD) is derived for a spherical shell head model. The result shows that they are related by a function of spatial frequency. For practically available low spatial frequencies, they are approximately linearly related to each other, so the SL estimate may be considered as an approximate SCD estimate in practice.
18 citations
TL;DR: In this paper, the (Ba,Sr)TiO3 amorphous gel was prepared by sol-gel process and calcined in the 2.45 GHz multimode microwave furnace to synthesize nanopowder.
Abstract: The (Ba,Sr)TiO3 amorphous gel was prepared by sol-gel process and calcined in the 2.45-GHz multimode microwave furnace to synthesize (Ba,Sr)TiO3 nanopowder. The calcination temperature of the (Ba,Sr)TiO3 ceramic powders that convert the material into prevoskite phase can be reduced from 1100°C to 900°C, the nanopowder displays the highest sinterability. Using a new kind of insulator materials made of MgAl2O4–LaCrO3, the crack-free and dense (Ba0.80Sr0.20)TiO3 ceramics with fine grain size (<1 µm) were prepared by microwave sintering at 1310°C for 15 min. The fine (Ba,Sr)TiO3 ceramics sintered by microwave sintering technique display lower dielectric loss than that of conventional samples, indicating a reduction of the influence of defects with the microwave process.
TL;DR: A new fMRI signal model is presented, which assumes the independence of temporal courses of signal and noise in a tiny spatial domain, and a novel fMRI data processing method is presented: Neighborhood independent component correlation algorithm.
Abstract: Independent component analysis (ICA) is a newly developed promising technique in signal processing applications. The effective separation and discrimination of functional Magnetic Resonance Imaging (fMRI) signals is an area of active research and widespread interest. Therefore, the development of an ICA based fMRI data processing method is of obvious value both theoretically and in potential applications. In this paper, analyzed firstly is the drawback of the extant popular ICA-fMRI method where the adopted signal model assumes the independence of spatial distributions of the signals and noise. Then presented is a new fMRI signal model, which assumes the independence of temporal courses of signal and noise in a tiny spatial domain. Consequently we get a novel fMRI data processing method: Neighborhood independent component correlation algorithm. The effectiveness is elucidated through theoretical analysis and simulation tests, and finally a real fMRI data test is presented.
TL;DR: In this article, the quantum vibrational energy-spectra of amide-Is in alpha-protein molecules are calculated by using the discretely nonlinear Schrodinger equation and physical parameters appropriate to the systems on the basis of theory of bio-energy transport.
Abstract: The quantum vibrational energy-spectra of amide-Is in alpha-protein molecules are calculated by using the discretely nonlinear Schrodinger equation and physical parameters appropriate to the systems on the basis of theory of bio-energy transport. The numerical results for the energy-spectra are basically consistent with the experimental values obtained by the infrared absorption and Raman scattering and emission-spectra of infrared lights of person's hand-fingers. Utilizing the energy-spectra we explain the laser-Raman spectrum from metabolically active E. Coli, and give some features of the infrared absorption of the protein molecules.
TL;DR: In this paper, a new type of partial dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT) is presented.
Abstract: A new type of partial-dielectric-loaded helical groove slow-wave structure (SWS) for millimetre wave travelling wave tube (TWT) is presented in this paper. The radio-frequency characteristics including the dispersion properties, the longitudinal electric field distribution and the beam-wave coupling impedance of this structure are analysed. The results show that the dispersion of the helical groove circuit is weakened, the phase velocity is reduced and the position of the maximum Ez is moved from the mouth to the inside of the groove after partially filling the dielectric materials in the helical groove SWS. Therefore, the dielectric-loaded helical groove SWS is suitable for a multi-beam TWT with broad band and high gain.
TL;DR: In this paper, a simple method is proposed to dispose the quantum effect and anharmonic effect at the same time, where the potential energy of an atom is expanded harmonically to consider the quantum effects of solids within the harmonic oscillator framework.
TL;DR: In this article, the deformation of the cantilever actuator under the influence of the magnetostrictive film thickness has been extensively studied, and it was shown that there exists a maximum deformation when the thickness of the film is properly chosen.
TL;DR: Based on solid phase reaction theory, an ultra-thin PtSi film of thickness 4nm is obtained using vacuum annealing and wet etching in this article, which has advantages in terms of low reaction temperature and short reaction time.
TL;DR: In this article, the effect of the deposition rate on the superconducting transition properties, c-axis lattice constant, concentration of lattice disorder and surface smoothness of YBCO thin films was studied.
Abstract: The dependence of YBCO thin film properties on the deposition rate was studied in this report. The thermodynamic growth parameters (substrate temperature, total pressure and oxygen partial pressure) were optimized at a fixed deposition rate first. Then keeping the thermodynamic growth parameters optimized values, YBCO thin films were deposited at different deposition rates. The effect of the deposition rate on the superconducting transition properties, c-axis lattice constant, concentration of lattice disorder and surface smoothness of YBCO thin films was studied. The measurements show that the optimized thermodynamic growth parameters are closely correlated to the deposition rate. At a fixed deposition rate of 0.5 A/s and its optimal thermodynamic growth parameters, YBCO thin films with superior superconducting transition temperature, the lowest concentration of lattice disorder, and the lowest surface roughness were prepared. By using the same thermodynamic growth parameters, changes in deposition rate were shown to degrade the superconducting transition temperature, increase the lattice disorder, and increase the roughness of the YBCO thin films.
TL;DR: A mathematical framework of estimating the error bounds of optimal combined forecasting (OCF) and the super-bound of nonoptimal combined forecasting errors and the relationships between the errors of the general combined forecasting method (including the simple average method) andThe errors of each forecasting model in the combination by mathematics analysis are given.
TL;DR: In this article, the dispersion equation and coupling impedance of a coaxial helical-groove structure are given. And the authors show that the cold bandwidth of this structure can reach 60%, while the coupling impedance is more than 16 /spl Omega.
Abstract: A coaxial helical-groove structure is presented and analyzed in this paper. The dispersion equation and coupling impedance of the structure are given. Numerical calculations of the dispersion relation and coupling impedance with different structure dimensions are carried out. Calculated results indicate that the cold bandwidth of this structure can reach 60%, while the coupling impedance is more than 16 /spl Omega/. It is shown that the coaxial helical groove is a wide-band slow-wave structure with high-power capacity.
TL;DR: This paper presents a scalable and high speed switching fabrics for Internet routers using wornihole routing and virtual channel in torus network to achieve a high-speed and scalable switching fabric for Internet router.
Abstract: Bandwidth demand in Internet is growing at a very fast rate. While links can provide the requested bandwidth, the situation is much more critical for routers. The design of high-speed switching fabric is a crucial part in current routers and switches. This paper presents a scalable and high speed switching fabrics for Internet routers— —torus network, which was mainly used in high performance computers before. Using wornihole routing and virtual channel in torus network can achieve a high-speed and scalable switching fabric for Internet router. In this paper, the performance of 4 X 3 X 2 3D torus network was analyzed as a core switching fabric for Internet routers. A novel dynamic and distribute routing algorithm is employed at switching system. We achieved an analysis model in OPNET simulation tools. Throughput and latency characteristic can be analyzed through this model. Simulation results show that maximal throughput is close to 100% under uniform traffic with low latency. It was found that using this architecture can reach Tera-bit capacity switching fabric and can be expanded from 36OGbit/s to 1.6 Tbit/s without increasing the link speed between nodes. At last, this paper presents some exciting directions in which the work can be extended.
TL;DR: A novel adaptive predistorter for linearizing a power amplifier in a mobile transmitter is studied and is shown to attain superior performance in comparison with other most well‐known predistortion structures.
Abstract: A novel adaptive predistorter for linearizing a power amplifier in a mobile transmitter is studied. Unlike most other predistorters reported in the literatures, this predistorter is constructed as a complex-valued recurrent neural network (RNN). The weights of the RNN were adjusted by using complex real time recurrent learning (RTRL) algorithm. Thus the AM/AM and AM/PM responses of the proposed predistorter are simultaneously implemented. The proposed scheme is shown to attain superior performance in comparison with other most well-known predistortion structures. The performance of the proposed predistorter is demonstrated through computer simulations. © 2002 John Wiley & Sons, Inc. Int J RF and Microwave CAE 12: 125–130, 2002.
TL;DR: In this article, the authors confirm that the thermally biological effect is a result produced by disorder motions of bio-water-molecules according to the essence of heat, feature of molecular structure of water, theory of molecular physics, principle of resonante absorption and experimental fact that infrared light can heat liquid water.
Abstract: thermally biological effects of infrared lights absorbed have been studied by nonlinear quantum theory and molecular biological theory on the basis of structures of cell and water molecules. There is a large number of water in the living systems, it play an important role in living activity, and has a lot of biological functions. There would be no life without water. We can confirm that the thermally biological effect is a result produced by disorder motions of bio-water-molecules according to the essence of heat, feature of molecular structure of water, theory of molecular physics, principle of resonante absorption and experimental fact that infrared light can heat liquid water. Therefore, mechanism of this effect is that the infrared light absorbed results in the quantum vibrations of water molecules with hydrogen bonds, the vibrational energy again transformes as thermal energy of disorder motions of a great number of water molecules in the living systems. The heating waters can cause a lot of biological effects and phenomena to occur in the living systems. Therefore, the infrared lights absorbed by the living systems have some medical functions.
TL;DR: In this article, a novel reconfigurable millimeter-wave leaky-wave antenna is proposed according to the radiation characteristics of periodically loaded coplanar waveguide and simulated by the finite-difference time-domain method.
Abstract: A novel reconfigurable millimeter-wave leaky-wave antenna is proposed according to the radiation characteristics of periodically loaded coplanar waveguide and simulated by the finite-difference time-domain method. The simulated results demonstrate that the single main beam of this antenna operating at 35.0GHz can scan with small steps in the E-plane from −90° to 90° except the angle around 0°. The main beam scanning is obtained by the antenna structure reconfiguration with nine discrete states controlled by embedded switches and two feed ports. The antenna is useful for millimeter-wave applications.
TL;DR: In this paper, a new chemical field effect transistor (ChemFET) gas-sensing device was fabricated by depositing the Pr(Pc * ) 2 /OA (1:3 molar ratio) mixed LB film on the gate area of MOSFET replacing the gate metal.
TL;DR: In this article, a totally inclusive cubic equation of state (cubic EOS) is proposed, which can include all of them as special cases, and the temperature coefficients of the five parameters for 43 substances are determined by fitting the experimental data of vapor pressure and saturated liquid density.
TL;DR: In this article, the quantum energy spectra, including high excited states, of vibrational amide-I or of intramolecular excitations in α-helical protein molecules, are calculated by the discrete nonlinear Schrodinger equation together with the parameters appropriate to the systems.
Abstract: The quantum energy spectra, including high excited states, of vibrational amide-I or of intramolecular excitations in α-helical protein molecules, are calculated by the discrete nonlinear Schrodinger equation together with the parameters appropriate to the systems. The distribution of energy levels obtained is basically consistent with the experimental values obtained by infrared absorption and Raman scattering. Utilizing the energy spectra we explain the laser Raman spectrum from metabolically active escherichia coli and we present some further features of the infrared absorption of the protein molecules.
TL;DR: A multiuser detector based on the tabu learning method, which applies the concept of tabu search to neural networks for solving optimization problems, is proposed.
26 Jun 2002
TL;DR: The problems of group key management and access control for large dynamic multicast groups have been researched and a solution based on subgroup secure controllers is given which solves many problems in IOLUS System, WGL scheme and many other solutions.
Abstract: With the proliferation of electronic commerce, multicast applications are beginning to be deployed for mainstream use and multicast technology will play a prominent role on the e-commerce applications in the coming years. Now, the academic research on multicast technology has become an active focus. Many results referring to multicast security have been gotten. But to date, efficient solutions, especially about the group key management, are very few. In this paper, the problems of group key management and access control for large dynamic multicast groups have been researched. We give a solution based on subgroup secure controllers, which solves many problems in IOLUS System, WGL scheme and many other solutions.
TL;DR: In this paper, a rigorous analysis for a microstrip cross is presented by using 2D generalized transmission-line equations, derived from circuit theory, while the equation coefficients are determined from full-wave numerical solutions.
Abstract: In this paper, a rigorous analysis for a microstrip cross is presented by using 2D generalized transmission-line equations The 2D generalized transmission-line equation is developed from the 1D generalized transmission-line equation in [1], which was derived from circuit theory, while the equation coefficients are determined from full-wave numerical solutions Although 1D generalized transmission-line equation can well model many microstrip structures, such as discontinuities and low-pass filters, it is confined to be used for those structures which can be regarded as 1D finite-length nonuniform transmission-line For a microstrip cross, the novel 2D generalized transmission-line equation whose coefficients are determined by dynamic numerical methods can have broadband frequency characteristics For the investigated microstrip cross, the S parameters for a frequency band from 4 GHz to 24 GHz can be calculated by using only one group of the 2D generalized equation at frequency of 14 GHz © 2002 Wiley Periodicals, Inc Microwave Opt Technol Lett 35: 378–380, 2002; Published online in Wiley InterScience (wwwintersciencewileycom) DOI 101002/mop10613