Showing papers by "University of Electronic Science and Technology of China published in 2000"
TL;DR: In this article, the authors present a theoretical analysis on a performance index W for chaotic spreading sequences, which characterizes the multiple access interference introduced by crosscorrelation of a sequence set in asynchronous DS/CDMA systems.
Abstract: The authors present a theoretical analysis on a performance index W for chaotic spreading sequences, which characterizes the multiple access interference introduced by crosscorrelation of a sequence set in asynchronous DS/CDMA systems. Using the ergodic theory, W is expressed in terms of ensemble-averaged autocorrelation functions and simple explicit formulae for W are obtained, under the assumption of independent seeds. Based on this analysis one can design chaotic spreading sequences performing better than ideal random sequences with respect to multiple access interference.
78 citations
TL;DR: In this article, a molecular self-assembling process based on the alternate deposition of polyaniline (PAN) and isopolymolybdic acid (PMA) from their dilute solutions was proposed.
Abstract: Electroactive nanocomposite ultrathin films of polyaniline (PAN) and isopolymolybdic acid (PMA) were fabricated by a novel molecular self-assembling process based on the alternate deposition of PAN and PMA from their dilute solutions. The process was based on doping-induced deposition effect of emeraldine base. The process was monitored by UV/VIS spectroscopy measurement. It was found that the conductivity of the PAN films is sensitive to humidity, NO2 and NH3. The technique may be used to fabricate chemical sensors and other molecular devices.
61 citations
TL;DR: In this paper, the Davydov model with a quasicoherent two-quanta state and a new interaction term in the Hamiltonian was used to describe bioenergy transport along the molecular chains in protein molecules by a soliton mechanism.
Abstract: The Hamiltonian and the wave function in the Davydov theory have simultaneously been improved and extended, based on some physical and biological grounds and on results from other models. The equations of motion for the improved Davydov model with a quasicoherent two-quanta state and a new interaction term in the Hamiltonian describe bioenergy transport along the molecular chains in protein molecules by a soliton mechanism. Some elementary properties of the soliton, including the nonlinear coupling energy and greatly increased binding energy of the soliton, are also given. The results obtained suggest that the model could be a candidate for a bioenergy transport mechanism in protein molecules.
60 citations
TL;DR: In this article, a variational Born iteration method (VBIM) was proposed for electromagnetic inverse scattering, which shows its efficiency much better than the distorted Born iterative method.
Abstract: A new iteration method for electromagnetic inverse scattering is presented. This method, called the variational Born iteration method (VBIM), shows its efficiency much better than the distorted Born iteration method. VBIM has also been used for hybrid iteration inversion. Moreover, the analytic characteristics of the numerical mode match (NMM) solution were used in the inversion integral equation to speed up the calculation. Some procedures to gain the stability of the inverse solution are also discussed.
54 citations
TL;DR: In this article, the authors investigated the mechanism of the formation of ionic and bonding defects and the interaction between protons and heavy ions in hydrogen-bonded molecular systems.
Abstract: The mechanism of the formation of ionic and bonding defects and the interaction between protons and heavy ions in hydrogen-bonded molecular systems is investigated and a new model is constructed. This model considers two coupled sublattices corresponding to those of protons and heavy ions in order to study the dynamic properties resulting from deformation and local fluctuation of the heavy ion sublattice due to the protonic displacements. As compared with other models, the model emphasizes, in particular, the collective effect of the motion and the mutual correlation between the two sublattices. The equations of motion admit analytic soliton solutions of different types corresponding to two different defects. The combined effect of the two defects and the proton transfer in the system are described by means of these solutions, and the appropriate conditions associated with actual physical processes. Finally, we discuss in detail the characteristics of the proton transfer and the advantages of the model.
52 citations
TL;DR: The theoretical simulation study of the spatial filters and mappings indicate that all 5 mappings provide higher resolution imaging maps of brain electrical activity than the scalp potential map, and an empirical VEP data study shows that any one of the5 mappings also provides higher spatial resolution than the forehead potential map.
47 citations
TL;DR: The ultrathin films of polyaniline (PAni)/poly (styrenesulfonic acid)(PSSA) were fabricated via a self-assembling process by alternately immersing the substrates into dilute PAni solution in N-methylpyrrolidinone (NMP) and the aqueous solution of PSSA as discussed by the authors.
38 citations
TL;DR: This paper introduces two novel methods for signal extraction and denoising through the use of the wavelet transform scale space filtering and Bayes shrinkage and obtains the best signal estimate through the Bayesian posterior analysis technique.
33 citations
TL;DR: In this paper, a submicrometer thin film of polypyrrole is prepared by electrolytic polymerization method and the best technological condition of preparing the sub-micrometers NH3-gas sensitive poly pyrrole thin film is found by researching into the technological parameters of electrolytic polymers.
Abstract: In this paper, submicrometer thin film of polypyrrole is prepared by electrolytic polymerization method. The best technological condition of preparing the submicrometer NH3-gas sensitive polypyrrole thin film is found by researching into the technological parameters of electrolytic polymerization. The NH3-gas sensitivity of polypyrrole is studied and the microstructure of this material is also discussed. Finally, adopting semiconductor theory, the NH3-gas sensitive mechanism of polypyrrole is extensively studied.
29 citations
TL;DR: In this article, the gas-sensitive properties of composite film are related to their micro-structures, and the porous structure in composite film would aid diffusion and therefore decrease the response time.
Abstract: Morphology and gas sensitive properties of composite films have been studied. Graphite/silicone rubber composite system exhibits better gas-sensitive response properties than those of carbon-black/silicone rubber system. Analysis of composite morphology indicates poor gas-sensitive response properties of carbon-black/silicone rubber system may be due to the presence of carbon gel, because carbon gel would hamper swelling effect of composite. It shows that gas-sensitive properties of composite film are related to their microstructures. Porous structure in composite film would aid diffusion and therefore decrease the response time
23 citations
TL;DR: In this paper, a prototype capacitor-type humidity sensor was designed and fabricated by a layer-by-layer self-assembling technique, which consists of a self-assembled electrically conductive polyaniline film and an insulating polyelectrolyte film which act as the top electrode and the dielectric layer, respectively.
TL;DR: In this paper, the nonlinear quantum vibrational energy spectra of amide-I in the molecular crystals acetanilide are calculated by using the discrete nonlinear Schrodinger equation appropriate to this kind of crystals.
Abstract: The nonlinear quantum vibrational energy spectra of amide-I in the molecular crystals acetanilide are calculated by using the discrete nonlinear Schrodinger equation appropriate to this kind of crystals. The numerical results obtained by this method are in good agreement with the experimental values. Meanwhile, the energy levels at high excited states have also been obtained for the acetanilide, which is helpful in researching the Raman scattering and infrared absorption properties of the this kind of crystals.
TL;DR: In this paper, a Smith-Purcell FEL with a relativistic electron beam of middle energy and a quasi-optical resonator composed of diffraction grating and three mirror reflectors is described.
Abstract: A novel Smith-Purcell FEL with a relativistic electron beam of middle energy and a quasi-optical resonator composed of diffraction grating and three mirror reflector is described in this paper. Coherent radiation with peak power of tens of KW at 3 mm waveband is successfully detected from an experimental facility characterized by beam energy of 400-500 KeV, pulse length of 70 ns, pulse beam current of 0.2 KA, and pulse guide magnetic field of up to 1.2 T.
28 Jun 2000
TL;DR: A rotary machinery fault diagnosis approach using the rough set theory is proposed based on the vibration characteristic spectrum, and the inherent redundancy in the spectrum information is revealed.
Abstract: Rotary machinery fault diagnosis can be treated as a pattern classification task. Based on the vibration characteristic spectrum, a rotary machinery fault diagnosis approach using the rough set theory is proposed. Accurate diagnostic results can be obtained directly from a set of complete fault spectrum samples; satisfactory diagnostic results can also be derived from a set of incomplete fault spectrum samples using the approach. The inherent redundancy in the spectrum information is revealed. The approach presents a new idea to rotary machinery fault diagnosis based on incomplete characteristics. Examples show that the proposed approach is very effective.
TL;DR: In this paper, an analytical transient turn-off current model for a type of the conductivity modulation power MOSFET transistors with the extracted structure of the excess carrier is developed.
Abstract: An analytical transient turn-off current model for a type of the conductivity modulation power MOSFET transistors (CMT) with the extracted structure of the excess carrier is developed in the paper. With the non-quasi-static state (NQS) approximation for the excess carrier in the wide base of a low gain pnp transistor included in the CMT the three state equations of the charge, the voltage and the current are solved for the transient turn-off current analysis and ambipolar transport theory in high-level injection is used to evaluate the steady state current. Accounting for the perturbing effect of the carrier concentration redistribution under the condition of base width modulation and the coupling effect between the electron and hole current, the normalized transient current and turn-off time of the device with the extracted structure are obtained and compared with the experimental results.
TL;DR: In this article, an anisotropy etching process of YAG has been developed for the fabrication of a YAG luminescent screen with truncated square mesas, and an improvement in phosphor efficiency by a factor of 2.3 has been achieved.
TL;DR: In this paper, the expressions of the dispersion equation and the coupling impedance of the hole-gap helical groove waveguide were obtained by means of an approximate field theory, and the influence of various circuit dimensions on dispersion relation and coupling impedance was discussed by the numerical computation.
Abstract: The hole-gap helical groove waveguide, as a all-metal slow-wave circuit, has advantages of good heat dissipation and great size, and thus is suitable for use of mm TWT. By means of an approximate field theory, the expressions of the dispersion equation and the coupling impedance of the hole-gap helical groove waveguide is obtained in this paper. The influence of various circuit dimensions on the dispersion relation and the coupling impedance is discussed by the numerical computation.
TL;DR: In this paper, the Conchoid of Nicomedes and Limacon of Pascal have been used as boundaries of static fields or high frequency waves for high power transmission in high frequency.
Abstract: Groove guides have sharp corners in the guide proper so are not low loss and high power carrying wave guides. Proposed has been a groove rectangular waveguide with rounded internal angles [1]. However, the latter is not practical in having the infinite arms. Let us try the Conchoid of Nicomedes and Limacon of Pascal to see how can they be boundaries of static fields or high frequency waves. Also has been proposed the pentagon waveguide [2] for the high power transmission in high frequency. Yet we feel that we have very limited forms of waveguides, so we study the existing curves to see whether we can find some better guides such as rounded corner rectangular waveguide and others by starting from the boundary curves of p = a/ cos φ + l and p = a cos φ + l.
TL;DR: In this paper, an electromagnetic particle-in-cell code has been used to simulate the nonlinear beam wave interaction and other optimization issues of a X-band RBWO with variable couple impedance, the simulation results show: the device can high-efficiently generate microwave radiation of 950MW peak power at (9.06±O).
Abstract: An electromagnetic particle-in-cell code has been used to simulate the nonlinear beam wave interaction and other optimization issues of a X-band RBWO with variable couple impedance, the simulation results show: the device can high-efficiently generate microwave radiation of 950MW peak power at (9.06±O.03) GHz when it is driven by a 5KA-500KV annular electron beam, peak power efficiency is 38%. The preliminary experiment results show that the microwave-generating efficiency of the non-uniform impedance RBWO is about twice of the uniform case in the same operating conditions.
12 Sep 2000
TL;DR: The configuration of the radar system and the techniques used in the system, including frequency sweep linearization, system background rejection, dynamic range compression and segments processing, are presented.
Abstract: The experimental result of two-dimensional imaging of an airfield object by LFMCW millimeter-wave radar is presented. The configuration of the radar system and the techniques used in the system, including frequency sweep linearization, system background rejection, dynamic range compression and segments processing, are presented.
Journal Article•
TL;DR: In this paper, based on the fourth-order cumulant matrix, a new sub-space decomposition algorithm is proposed for the EEG inverse problem, which shows its better performance than the two- order cumulate method in depressing the spatial coherent Gaussian noise.
TL;DR: An inference method for fuzzy tree grammars is given, which is composed of two parts: first, a fuzzy expansive tree grammar is generated from a sample set; second, the grammar is simplified.
TL;DR: Based on fourth-order cumulant and ESPRIT algorithm, a novel joint frequency, two-dimensional angle of arrival (2D AOA) and the polarization estimation method of incoming multiple independent spatial narrow-band nowGaussian signals in arbitrary Gaussian noise environment are proposed in this article.
Abstract: Based on fourth-order cumulant and ESPRIT algorithm, a novel joint frequency, two-dimensional angle of arrival (2D AOA) and the polarization estimation method of incoming multiple independent spatial narrow-band nowGaussian signals in arbitrary Gaussian noise environment are proposed. The array is composed of crossed dipoles parallel to the coordinate axes. The crossed dipole positions are arbitrarily distributed. Computer simulation confirms its feasibility.
TL;DR: In this paper, the non-linear relation between absorption coefficients and continuous scattered intensity is fitted by a quadratic equation for a wide range of matrix absorption, and a more suitable absorption correction method compared with the traditional scattered internal technique is recommended for matrix absorption correction in X-ray fluorescence spectrometry.
TL;DR: In this article, the results of an experiment to produce high-power microwave radiation from a gas-filled backward wave oscillator (BWO) driven by a relativistic electron beam without external guiding magnetic field were reported.
Abstract: Reported in this paper are the results of an experiment to produce high-power microwave radiation from a gas-filled backward wave oscillator (BWO) driven by a relativistic electron beam without external guiding magnetic field. A peak power for background gas pressure at 5.25 mTorr has been observed as argon pressure from 0.75 mTorr to 15 mTorr. Operating frequency of the oscillator has been measured at 9.6 ± 0.4 GHz. The results of PIC simulation are in good agreement with the experimental results. A reasonable explanation is given for experimental results by PIC simulation.
30 Oct 2000
TL;DR: A theoretic model on fuzzy knowledge representation and exchange is presented, in which some key problems such as fuzzy belief composition and contradiction coordination are solved and it is proved the model's availability and efficiency.
Abstract: A multi-MA (mobile agents) cooperative system leads to flexible and efficient solutions for distributed systems, but a lot of research is not suitable for dynamic network environments. Based on the modeling of the multi-MA cooperative system and analysis of MA behavior, we present some new ideas and a theoretic model on fuzzy knowledge representation and exchange, in which some key problems such as fuzzy belief composition and contradiction coordination are solved. With the help of simulation experiments on dynamic network topology discovery, we prove the model's availability and efficiency.
TL;DR: In this paper, a two-step self-template method was used to obtain high-axis-oriented epitaxial YBa 2 Cu 3 O 7− δ (YBCO) thin films for microwave applications.
Abstract: Highly c -axis-oriented epitaxial YBa 2 Cu 3 O 7− δ (YBCO) thin films prepared on LaAlO 3 substrates by a self-template technique have been investigated for microwave applications. By varying the conditions of the two-step self-template method, the properties of YBCO thin films could be improved significantly. With this method, it was easy to reproducibly obtain YBCO thin films with T c 0 ≥90 K, Δ T c ≤1 K, R s (77 K, 10 GHz)∼500 μΩ. The best sample grown under optimal conditions had a low R s of 330 μΩ at 77 K and 10 GHz. In addition, the correlation between the microwave surface resistance, R s , and the crystal structure is discussed by studying the electron channeling pattern (ECP) of thin films. In conclusion, the microwave losses can strongly be affected by structural imperfections.
TL;DR: In this paper, the growth of purely (001) oriented single crystal Y1Ba2Cu3O7−x thin films with excellent crystal perfection by afterglow plasma sputtering was reported.
TL;DR: In this article, the influence of the squeezing-antisqueezed effect of phonons arising from polaron motion on the ground state in strongly coupled electron-phonon systems with high and low electron-densities was studied by a new state ansatz including the correlated effects among displacement and squeezing of phonon and polarons in the Holstein model.
TL;DR: In this paper, a new criterion for nonsingularity of matrices and a monotonic iterative method for matrix 1-balancing problems were proposed. But these methods are not suitable for the problem of matrix 1 balancing.