Showing papers by "University of Electronic Science and Technology of China published in 2003"
TL;DR: It is shown that fractional-order chaotic oscillators can be synchronized with appropriate coupling strength and is numerically demonstrated using the master-slave synchronization scheme.
Abstract: The chaotic dynamics of fractional order systems began to attract much attention in recent years. In this Brief Report, we study the master-slave synchronization of fractional order chaotic systems. It is shown that fractional order chaotic systems can also be synchronized.
194 citations
TL;DR: Conditions based on local inhibition are derived that guarantee boundedness of some multistable networks, conditions are established for global attractivity, bounds on global attractive sets are obtained, and complete convergence conditions for the network are developed using novel energy-like functions.
Abstract: Multistability is a property necessary in neural networks in order to enable certain applications (e.g., decision making), where monostable networks can be computationally restrictive. This article focuses on the analysis of multistability for a class of recurrent neural networks with unsaturating piecewise linear transfer functions. It deals fully with the three basic properties of a multistable network: boundedness, global attractivity, and complete convergence. This article makes the following contributions: conditions based on local inhibition are derived that guarantee boundedness of some multistable networks, conditions are established for global attractivity, bounds on global attractive sets are obtained, complete convergence conditions for the network are developed using novel energy-like functions, and simulation examples are employed to illustrate the theory thus developed.
89 citations
20 Oct 2003
TL;DR: A honeypot is a supplemented active defense system for network security that traps attacks, records intrusion information about tools and activities of the hacking process, and prevents attacks outbound the compromised system.
Abstract: A honeypot is a supplemented active defense system for network security. It traps attacks, records intrusion information about tools and activities of the hacking process, and prevents attacks outbound the compromised system. Integrated with other security solutions, a honeypot can solve many traditional dilemmas. We expatiate key components of data capture and data control in a honeypot, and give a classification for honeypots according to security goals and application goals. We review the technical progress and security contribution of production honeypots and research honeypots. We present typical honeypot solutions and predict the technical trends of integration, virtualization and distribution for future honeypots.
87 citations
TL;DR: Simulations showed that the new temporal ICA method is more effective than the spatial ICA in detecting weak signal in a fMRI dataset and that the excited areas evoked by a visual stimuli are mainly in the region of the primary visual cortex.
Abstract: Independent Component Analysis (ICA) is a promising tool for the analysis of functional magnetic resonance imaging (fMRI) time series. In these studies, mostly assumed is a spatially independent component map of fMRI data (spatial ICA). In this paper, we assume that the temporal courses of the signal and noises are independent within a Tiny spatial domain (temporal ICA). Then with fast-ICA algorithm, spatially neighboring fMRI data were blindly separated into several temporal courses and were preassumed to be formed by a signal time course and several noise time courses where the signal has the largest correlation coefficient with the reference signal. The final functional imaging was completed for the signals obtained from each voxel. Simulations showed that compared with the spatial ICA method, the new temporal ICA method is more effective than the spatial ICA in detecting weak signal in a fMRI dataset. As background noise, the simulations include simulated Gaussian noise and fMRI data without stimulation. Finally, vivo fMRI tests showed that the excited areas evoked by a visual stimuli are mainly in the region of the primary visual cortex and that evoked by auditory stimuli are mainly in the region of the primary temporal cortex.
57 citations
TL;DR: A novel dynamic grooming graph is proposed which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources within a WDM grooming mesh network.
Abstract: Within a WDM grooming mesh network and under the constraints of the number of transceivers per node and wavelength continuity, we propose a novel dynamic grooming graph which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources. Based on the grooming graph, we first propose a dynamic traffic-grooming algorithm called integrated grooming algorithm (IGA). And we also propose two dynamic survivable traffic-grooming algorithms, which are called protection per lightpath traffic-grooming algorithm (PPL) and protection per connection traffic-grooming algorithm (PPC). These algorithms are evaluated via simulations.
54 citations
TL;DR: A neural network model with weighted small-world connections is presented and the stability of this model is investigated to help characterize biological neural networks, in which there are different weights in synaptic connections.
Abstract: Small-world networks are highly clustered networks with small distances among the nodes. There are many biological neural networks that present this kind of connection. There are no special weightings in the connections of most existing small-world network models. However, this kind of simply connected model cannot characterize biological neural networks, in which there are different weights in synaptic connections. In this paper, we present a neural network model with weighted small-world connections and further investigate the stability of this model.
54 citations
TL;DR: In this article, a frequency-reconfigurable patch antenna is proposed and analyzed using the finite-difference time-domain (FDTD) method, and simulated results indicate that the antenna is capable of shifting its operating frequency over a one-octave bandwidth from 0.6 GHz to 1.2 GHz with the radiation pattern essentially unaffected by the frequency tuning.
Abstract: A novel frequency-reconfigurable patch antenna is proposed and analysed using the finite-difference time-domain (FDTD) method. The simulated results indicate that the antenna is capable of shifting its operating frequency over a one-octave bandwidth from 0.6 GHz to 1.2 GHz with the radiation pattern essentially unaffected by the frequency tuning. © 2003 Wiley Periodicals, Inc. Microwave Opt Technol Lett 36: 295–297, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.10746
45 citations
TL;DR: The algorithm is applied to some examples and the results demonstrate that GADSO is able to produce highly conformal dose distributions using 20-30 deliverable segments per treatment within a clinically acceptable computation time.
Abstract: The static delivery technique (also called step-and-shoot technique) has been widely used in intensity-modulated radiotherapy (IMRT) because of the simple delivery and easy quality assurance Conventional static IMRT consists of two steps: first to calculate the intensity-modulated beam profiles using an inverse planning algorithm, and then to translate these profiles into a series of uniform segments using a leaf-sequencing tool In order to simplify the procedure and shorten the treatment time of the static mode, an efficient technique, called genetic algorithm based deliverable segments optimization (GADSO), is developed in our work, which combines these two steps into one Taking the pre-defined beams and the total number of segments per treatment as input, the number of segments for each beam, the segment shapes and weights are determined automatically A group of interim modulated beam profiles quickly calculated using a conjugate gradient (CG) method are used to determine the segment number for each beam and to initialize segment shapes A modified genetic algorithm based on a two-dimensional binary coding scheme is used to optimize the segment shapes, and a CG method is used to optimize the segment weights The physical characters of a multileaf collimator, such as the leaves interdigitation limitation and leaves maximum over-travel distance, are incorporated into the optimization The algorithm is applied to some examples and the results demonstrate that GADSO is able to produce highly conformal dose distributions using 20-30 deliverable segments per treatment within a clinically acceptable computation time
42 citations
TL;DR: A class of digital filters, called interpolated finite impulse response (IFIR) filters that can implement narrowband lowpass FIR filter designs with a significantly reduced computational workload relative to traditional FIR filters are described.
Abstract: The article describes a class of digital filters, called interpolated finite impulse response (IFIR) filters that can implement narrowband lowpass FIR filter designs with a significantly reduced computational workload relative to traditional FIR filters. Topics discussed include: optimum expansion factor choice, number of FIR filter taps estimation, IFIR filter performance modeling, passband ripple considerations, implementation, and filter design.
42 citations
TL;DR: Without assuming symmetry of synaptic connection weights and monotonicity and differentiability of activation functions, Halanay-type inequalities are employed to derive the delay-independent sufficient conditions under which the networks converge exponentially to the equilibria associated with temporally uniform external inputs.
Abstract: In this paper, the dynamical characteristics of hybrid bidirectional associative memory neural networks with constant transmission delays are investigated. Without assuming symmetry of synaptic connection weights and monotonicity and differentiability of activation functions, Halanay-type inequalities (which are different from the approach of constructing Lyapunov functionals) are employed to derive the delay-independent sufficient conditions under which the networks converge exponentially to the equilibria associated with temporally uniform external inputs. Our results are less conservative and restrictive than previously known results.
41 citations
TL;DR: In this paper, the authors concentrate on the present state of study of four types of structures: helical groove, ring-plane, folded waveguide and periodically loaded waveguide, including theoretical analyses and practical applications.
Abstract: All-metal slow-wave structures are being paid great attention because of their advantages, such as good heat dissipation, high power capacity, wide passband, good wholeness of structure and large size etc. The emphases in this paper concentrate on the present state of study of four types of structures: helical groove, ring-plane, folded waveguide and periodically loaded waveguide, including theoretical analyses and practical applications. The problems and directions for future studies of these types of slow-wave circuits are also discussed. It is pointed out that all-metal slow-wave structures are suitable for applications in millimeter wave vacuum devices, like TWT, BWO, Gyro-TWT, and relativistic devices.
TL;DR: The thermal stability and electrical properties of Hf-silicate films have been investigated by diffraction, differential thermal analysis, atom force microscopy, x-ray photoelectron spectroscopy, capacitance-voltage (C-V) and leakage current voltage measurements as mentioned in this paper.
Abstract: Hf-silicate films were deposited directly onto n-type Si (100) substrates and Pt-coated Si substrates by a pulsed laser deposition technique using a ceramic Hf-silicate target. The thermal stability and electrical properties of Hf-silicate films have been investigated by x-ray diffraction, differential thermal analysis, atom force microscopy, x-ray photoelectron spectroscopy, capacitance–voltage (C–V) and leakage current–voltage (I–V) measurements. The amorphous structure of Hf-silicate films was found to be stable up to at least 900°C. A crystallization transformation from the amorphous phase to a polycrystalline tetragonal structure occurs under rapid thermal annealing for 3 min at 1000°C. The amorphous Hf-silicate film exhibits a high dielectric constant of about 14.1 measured in a Pt/Hf-silicate/Pt capacitor structure. The smoothness and electrical properties of films have been improved by rapid thermal annealing in N2 ambient at 900°C for 30 s. A very small equivalent oxide thickness of 0.95 nm for 2.6 nm Hf-silicate film on the n-Si substrate and a low leakage current of 24 mA cm−2 at 1 V gate voltage were obtained. Thus, Hf-silicate films with good thermal stability can be one of the most promising candidates for future high-k gate dielectric applications.
Patent•
29 Aug 2003TL;DR: In this paper, the authors proposed a method to implement optimum variation lateral flux on a semiconductor surface. But the method is not suitable for high-voltage lateral devices, and the edge termination technique for highvoltage vertical devices is not available.
Abstract: This invention provides a method or an auxiliary method to implement optimum variation lateral flux on a semiconductor surface. The method is to cover one or more thin films of high permittivity dielectric material on the semiconductor surface. The one or more films are capable of transmitting flux into or extracting flux from the semiconductor surface, or even to extract some flux from a part of the semiconductor surface and then transmit the flux to another part of the semiconductor surface. By using optimum variation lateral flux, not only can high-voltage lateral devices be made, but also an edge-termination technique for high-voltage vertical devices is provided. While the thin films can be used to prevent the occurrence of strong electric fields produced at the edges of some doped regions, these regions are used to compensate other doped regions with opposite doping and different location. Thin films can also be used to realize an optimum variation lateral flux of a lateral semiconductor device, which is located on a substrate and the flux flowing between the semiconductor and the substrate is negligibly small.
TL;DR: In this article, several simple criteria for nonsingular H-matrices are obtained by making use of elements of matrices only, and they are illustrated by numerical examples and a necessary condition is also presented.
TL;DR: This work develops forward density formulae for the ECL and the EDL of neural electric sources in a 4-concentric-sphere head model, and compares ECL with EDL in theory, simulation and real evoked data tests, and confirms that theECL map may be of higher spatial resolution than theEDL map.
Abstract: Brain electrical signal is one of the windows to understanding neural activities. Various high-resolution imaging techniques have been developed to reveal the electrical activities underneath the cortical surface from scalp electroencephalographic recordings, such as scalp Laplacian, cortical surface potential, equivalent charge layer (ECL) and equivalent dipole layer (EDL). In this work, we develop forward density formulae for the ECL and the EDL of neural electric sources in a 4-concentric-sphere head model, and compare ECL with EDL in theory, simulation and real evoked data tests. The results confirm that the ECL map may be of higher spatial resolution than the EDL map.
Journal Article•
TL;DR: In this paper, three adaptive traffic grooming algorithms are proposed, and a dynamic path-protection traffic grooming algorithm is also proposed to provide the survivable optical network with constraints on the number of transceivers and wavelength continuity.
Abstract: Traffic grooming, which can efficiently multiplex many low-rate traffic streams into one lightpath, has been a hot topic in the research community. Here adaptive routing and wavelength assignment (RWA) is studied for WDM grooming mesh networks with constraints on the number of transceivers and wavelength continuity. Three adaptive traffic-grooming algorithms are proposed, and a dynamic path-protection traffic-grooming algorithm is also proposed to provide the survivable optical network. The performance of these algorithms is assessed through simulations.
TL;DR: In this article, a new gas sensor has been fabricated by incorporating the multilayer Er[Pc*]2 LB film into the gate electrode of a MOSFET, forming an array of charge flow transistor (CFT).
01 Dec 2003
TL;DR: The paper proposes a new method, minimum clipping power loss scheme (MCPLS), to control the clipping noise based on the relationship between the power of clipped portion and the clip noise power of OFDM signals, which can mitigate clipping noise and improve the performance of the system.
Abstract: The paper proposes a new method, minimum clipping power loss scheme (MCPLS), to control the clipping noise based on the relationship between the power of clipped portion and the clipping noise power of OFDM signals. First, the transmitter generates multi-route signals that carry the same information then estimates the clipping noise power of every route under the same clipping threshold. The transmitter then selects the signal with the lowest clipping noise power to clip and transmits the signal. The simulation results proved that this method can mitigate clipping noise and improve the performance of the system. The signal-to-noise ratio is gained 8 dB to achieve 10/sub -3/ symbol-error-rate when the number of subcarriers is 256, the modulation mode is 16-QAM, the clipping threshold is 1.5 and the redundancy of system is 0.59%. The floor of symbol-error-rate is reduced from 10/sub -3/ to 3/spl middot/10/sub -5/. The arithmetic achieves better effect if the threshold is lower.
20 Oct 2003
TL;DR: This paper presents a new list scheduling scheme to schedule tasks of a DAG onto a homogeneous multiprocessors system, and its time-complexity is O(pv/sup 2/).
Abstract: Optimal scheduling of tasks of a directed acyclic graph (DAG) onto a set of processors is a strong NP-hard problem. Because list scheduling has shown good performance and is less difficult to design, it has been studied and used widely. We present a new list scheduling scheme to schedule tasks of a DAG onto a homogeneous multiprocessors system. The primary objective of this scheme is to minimize schedule length and scheduling time itself. We analyzed three typical list scheduling algorithms - MCP algorithm, ETF algorithm and BDCP algorithm, and find that they all cannot guarantee the earliest schedules of the CPNs. In this paper, we propose a better list scheduling algorithm based on critical path, and its time-complexity is O(pv/sup 2/). This algorithm always it is the most important purpose that schedule CPN as soon as it is a ready task, which makes the nodes that have the greatest influence to the scheduling length of the task graph be scheduled first. This greatly shortens the scheduling length of the task graph. We compare the performance of this algorithm with existing scheduling scheme through analysis and the result of experiments. The scheduling length generated by this algorithm is shorter than that of other scheduling algorithm.
TL;DR: In this paper, the two-step martensitic transformation temperatures were measured by differential scanning calorimeter and the results indicated that the temperature M s of the onset of R-phase-to-martensite transformation decreased with increasing electron dose.
15 Nov 2003-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a two-way shape memory effect (TWSME) spring that could elongate upon heating and contract upon cooling was obtained by constrained annealing and thermo-mechanical training.
Abstract: A two-way shape memory effect (TWSME) spring that could elongate upon heating and contract upon cooling was obtained by constrained annealing and thermo-mechanical training. The effect of heat treatment and thermomechanical training on the TWSME and the effect of training on the transformation temperatures had been studied by elongation-temperature, electrical resistance measurements and differential scanning calorimetry (DSC). The TWSME recovery rate of extension spring increases with increasing the training cycles and increases to a saturation value. The inverse martensitic and martensitic temperatures decreased with increasing thermo-mechanical training cycles. (C) 2003 Elsevier B.V. All rights reserved.
TL;DR: Comparisons show that the agreement of the model with the computer simulation data is slightly better than the mean spherical approximation and other analytic models.
Abstract: A simple analytic expression with high precision for the radial distribution function of hard spheres is proposed. The form of the expression has been carefully selected to combine the well-known Camahan-Starling equation of state in it and satisfy the limit condition at low density, its simplicity and precision is superior to the well-known Percus-Yevick expression. The coefficients contained in the expression have been determined by fitting the Monte Carlo data for the first coordination shell, and by fitting both the Monte Carlo data and the numerical results of the Percus-Yevick expression for the second coordination shell. The expression has been applied to develop simple analytic equations of state for the hard-core single, double Yukawa fluids, and the hard-core Yukawa mixtures. The comparisons show that the agreement of our model with the computer simulation data is slightly better than the mean spherical approximation and other analytic models.
TL;DR: In this article, the structural mechanisms of the hardening of a Ti-2Al-2.5Zr alloy by 75 keV nitrogen ion implantation with doses of 3×1017 and 8× 1017 N/cm2 are investigated.
TL;DR: An analytic expression of radial distribution function of hard spheres is developed in terms of a polynomial expansion of nonlinear base functions and the Carnahan-Starling equation of state (EOS).
Abstract: An analytic expression of radial distribution function of hard spheres is developed in terms of a polynomial expansion of nonlinear base functions and the Carnahan–Starling equation of state (EOS). The comparison with the Monte-Carlo data and the Percus-Yevick expression shows that the expression developed gives out better results. The expression is very simple that can make most perturbation theories become analytic ones, and a simple analytic EOS for the fluids with continuous exponential-six potential is established based on the Ross variational perturbation theory. The main thermodynamic quantities have been analytically derived, the resulting expressions are surprisingly simple, the variational procedure is greatly simplified and the calculations are absolutely convergent. The numerical results are compared with the Monte-Carlo data and the original non-analytic theory. It is shown that the precision of the analytic EOS is as good as the original non-analytic one.
TL;DR: In this paper, the effects of deposition temperature on the crystallization process of sputtering PZT film were described. But the results of X-ray diffraction (XRD) and atomic force microscopy (AFM) showed the crystalline structure, the surface morphology and the crystallographic orientations of PZTs films.
Abstract: The PZT thin film has been successfully prepared on Pt/Ti/SiO2/Si substrate by pulsed laser deposition. The target is of Pb(Zr052Ti0.48)O3 which has excess Pb. The PZT thin film thickness is between 200 and 500 nm while the buffer layer Ti is of 50 nm thick. This paper describes the effects of deposition temperature on the crystallization process of sputtering PZT film. X-ray diffraction (XRD) and atomic force microscopy (AFM) showed the crystalline structure, the surface morphology and the crystallographic orientations of PZT films. For electrical characterizations, the bottom electrode with width of 1.0 mm strip was formed by depositing the Ti/Pt on Si substrate and etching, the top electrode with same shape and width was formed by sputtering Pt but it was at right angles to the bottom electrode, so the ferroelectric capacitor had an area of 1.0×10−2 cm2. Ferroelectric properties of the capacitor has been characterized using a ferroelectric film tester (Radiant Technologies, RT66A). Process optimized PZT film has a coercive field of 45 kV cm−1 and a remanent polarization of 25 μC cm−2. The PZT film has perovskite structure.
TL;DR: In this article, a technique for growing high quality ZnO thin films by means of single source chemical vapor deposition (SS CVD) under low vacuum conditions with the precursor of zinc carbamate Zn4O(CO2Net2)6.
Abstract: A novel technique is developed for growing high quality ZnO thin films by means of single source chemical vapor deposition (SS CVD) under low vacuum conditions with the precursor of zinc carbamate Zn4O(CO2Net2)6. SEM, AFM and XRD studies show that the resultant thin films have high density, smooth surface, uniform polycrystalline structure and excellent c-axis orientation. XPS investigation indicates that the ZnO films are free of decomposed precursor residues in the bulk. Careful quantitative XPS analysis reveals that the ZnO films are stoichiometric with O/Zn atomic ratio very close to that of ZnO single crystal.
TL;DR: In this article, a microsensor for nitrogen dioxide (NO2) fabricated by Langmuir-Boldgett (LB) films of Samarium bis[2,3,9,10,16,17,23,24-octakis(octyloxy)phthalocyaninato] complex and charge-flow transistor (CFT) is evaluated.
01 May 2003-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this paper, a broad absorption band centered at 522 or 497 nm was observed in the optical absorption spectra of samples implanted with Xe+-implanted yttria-stabilized zirconia (YSZ).
Abstract: Transmission electron microscopy (TEM), optical absorption and photo-luminescence spectroscopy were utilized to characterize the damage structure in 200 keV Xe+-implanted yttria-stabilized zirconia (YSZ). The implantation was conducted at room temperature up to a fluence of 1 × 1017 Xe+/cm2. TEM analysis showed that the density of defect clusters increased with increasing ion fluence. Small bubbles (3–5 nm in diameter) precipitated in the sample at a fluence of 1 × 1017 Xe+/cm2. No amorphization was observed. A broad absorption band centered at 522 or 497 nm was observed in the optical absorption spectra of samples implanted with 1 × 1016 Xe+/cm2 and 1 × 1017 Xe+/cm2, respectively. The band may be associated with the combination of electrons trapped at oxygen vacancies and oxygen ions with trapped holes. Luminescence measurements of the YSZ crystal implanted with 1 × 1016 Xe+/cm2 show that Xe+-implantation did not produce other optically active defects.
01 Oct 2003-Nuclear Instruments & Methods in Physics Research Section B-beam Interactions With Materials and Atoms
TL;DR: In this article, the parent phase (austenitic phase) was stabilized by the irradiation, since the R-phase transformation start temperature Rs and the reverse martensitic transformation finish temperature Af had decreased with increasing proton dose, about 6 K for Rs and 13 K for Af at a dose of 1.5×1014 H+/cm2.
Abstract: Ti-50.6at.%Ni shape memory alloy specimens were irradiated in the parent phase using a tandem accelerator by 18 MeV protons at a dose rate of 4.27 × 109 cm−2 s−1 for 1 h and 10 h, respectively. The total doses were 1.5 × 1013 and 1.5 × 1014 H+/cm2. Microstructures and phase transformation characteristics of the specimens before and after irradiations were evaluated by transmission electron microscopy and differential scanning calorimetry. There is no observable change of the microstructures after the irradiation. The parent phase (austenitic phase) was stabilized by the irradiation, since the R-phase transformation start temperature Rs and the reverse martensitic transformation finish temperature Af had decreased with increasing proton dose, about 6 K for Rs and 13 K for Af at a dose of 1.5 × 1014 H+/cm2. As and Rf were not affected by the proton irradiation. The variation of the transformation temperatures was assigned to local stress fields and changes in the degree of the lattice order produced by the proton irradiation.
22 Apr 2003
TL;DR: Theoretical and simulation results show that the optimum PDR is effected by the signal-to-noise ratio (SNR), Doppler frequency and interpolation size etc, and provide a suitable tool for system design.
Abstract: In this paper, the current analysis focuses on the demodulation performance in multipath fading propagation environments, which results from the pilot power variation of pilot symbol, assisted modulation (PSAM) M-PSK in orthogonal frequency division multiplexing (OFDM) systems. The pilot-to-data power ratio (PDR) is optimized analytically. Theoretical and simulation results show that the optimum PDR is effected by the signal-to-noise ratio (SNR), Doppler frequency and interpolation size etc, and provide a suitable tool for system design.