Showing papers by "University of Electronic Science and Technology of China published in 2004"
TL;DR: In this paper, the authors numerically studied the chaotic behaviors in the fractional-order Rossler equations and found that chaos and hyperchaos exist in such systems with order less than 3.
Abstract: The dynamics of fractional-order systems have attracted increasing attentions in recent years. In this paper, we numerically study the chaotic behaviors in the fractional-order Rossler equations. We found that chaotic behaviors exist in the fractional-order Rossler equation with orders less than 3, and hyperchaos exists in the fractional-order Rossler hyperchaotic equation with order less than 4. The lowest orders we found for chaos and hyperchaos to exist in such systems are 2.4 and 3.8, respectively. Period doubling routes to chaos in the fractional-order Rossler equation are also found.
617 citations
TL;DR: This paper introduces complex dynamical network models with coupling delays for both continuous- and discrete-time cases and investigates their synchronization phenomena and criteria, and derives synchronization conditions for both delay-independent and delay-dependent asymptotical stabilities in terms of linear matrix inequalities (LMI).
Abstract: Complex networks have attracted increasing attention from various fields of science and engineering today. Due to the finite speeds of transmission and spreading as well as traffic congestions, a signal or influence travelling through a complex network often is associated with time delays, and this is very common in biological and physical networks. In this paper, we introduce complex dynamical network models with coupling delays for both continuous- and discrete-time cases and then investigate their synchronization phenomena and criteria. Based on these new complex network models, we derive synchronization conditions for both delay-independent and delay-dependent asymptotical stabilities in terms of linear matrix inequalities (LMI). We finally use a network with a fixed delay and a specific coupling scheme as an example to illustrate the theoretical results.
583 citations
TL;DR: In this paper, the authors studied the chaotic behaviors in the fractional order Chen system and found that chaos exists in all the levels of the Chen system with order less than 3.1.
Abstract: In this letter, we study the chaotic behaviors in the fractional order Chen system. We found that chaos exists in the fractional order Chen system with order less than 3. The lowest order we found to have chaos in this system is 2.1. Linear feedback control of chaos in this system is also studied.
492 citations
TL;DR: In this paper, a graphite disc electrode in the acidic solution of KMnO4 resulted in the deposition of a redox active coating on the electrode surface, which exhibited typical pseudo-capacitive behaviour.
191 citations
TL;DR: By constructing several novel Lyapunov functionals, some sufficient criteria for the existence of a unique equilibrium and global exponential stability of the network are derived.
189 citations
24 Jul 2004
TL;DR: In this article, a delay-dependent robust stability criterion for Takagi-Sugeno fuzzy systems with time-varying delays and parameter uncertainties is given in terms of linear matrix inequalities by using the Lyapunov-Krasovskii functional method and by applying a generalised Park's inequality for bounding the cross-terms.
Abstract: The stability problem of Takagi-Sugeno fuzzy systems with time-varying delays and parameter uncertainties is considered. A delay-dependent robust stability criterion is given in terms of linear matrix inequalities by using the Lyapunov-Krasovskii functional method and by applying a generalised Park's inequality for bounding the cross-terms. Examples are given to illustrate the effectiveness of the result.
161 citations
TL;DR: In this paper an efficient method is presented to investigate how to improve the dose distributions by selecting suitable coplanar beam angles and the results show that ABAS is valid and efficient and can improve the doses distributions within a clinically acceptable computation time.
Abstract: The selection of suitable beam angles in external beam radiotherapy is at present generally based upon the experience of the human planner. The requirement to automatically select beam angles is particularly highlighted in intensity-modulated radiation therapy (IMRT), in which a smaller number of modulated beams is hoped to be used, in comparison with conformal radiotherapy. It has been proved by many researchers that the selection of suitable beam angles is most valuable for a plan with a small number of beams (≤5). In this paper an efficient method is presented to investigate how to improve the dose distributions by selecting suitable coplanar beam angles. In our automatic beam angle selection (ABAS) algorithm, the optimal coplanar beam angles correspond to the lowest objective function value of the dose distributions calculated using the intensity-modulated maps of this group of candidate beams. Due to the complexity of the problem and the large search space involved, the selection of beam angles and the optimization of intensity maps are treated as two separate processes and implemented iteratively. A genetic algorithm (GA) incorporated with an immunity operation is used to select suitable beam angles, and a conjugate gradient (CG) method is used to quickly optimize intensity maps for each selected beam combination based on a dose-based objective function. A pencil-beam-based three-dimensional (3D) full scatter convolution (FSC) algorithm is employed for the dose calculation. Two simulated cases with obvious optimal beam angles are used to verify the validity of the presented technique, and a more complicated case simulating a prostate tumour and two clinical cases are employed to test the efficiency of ABAS. The results show that ABAS is valid and efficient and can improve the dose distributions within a clinically acceptable computation time.
137 citations
TL;DR: In this paper, the columnar structure of ZnO thin films with respect to the incident angle prepared by single source chemical vapor deposition (SS CVD) on Si (1/0/0) substrate was examined.
123 citations
TL;DR: In this article, an effective back-stepping design is applied to chaos synchronization, such as the synchronization error is exponential convergent; only one variable information of the master system is needed; and a systematic procedure for selecting a proper controller.
Abstract: In recent years, backstepping method has been developed in the field of nonlinear control, such as controller, observer and output regulation. In this paper, an effective backstepping design is applied to chaos synchronization. There are some advantages in this method for synchronizing chaotic systems, such as (a) the synchronization error is exponential convergent; (b) only one variable information of the master system is needed; (c) it presents a systematic procedure for selecting a proper controller. Numerical simulations for the Chua's circuit and the Rossler system demonstrate that this method is very effective.
105 citations
TL;DR: In this paper, the stability of bifurcating periodic solutions and the direction of Hopf bifurbation are determined by applying the normal form theory and the center manifold theorem.
Abstract: We consider an Internet model with a single link accessed by a single source, which responds to congestion signals from the network, and study bifurcation of such a system. By choosing the gain parameter as a bifurcation parameter, we prove that Hopf bifurcation occurs. The stability of bifurcating periodic solutions and the direction of the Hopf bifurcation are determined by applying the normal form theory and the center manifold theorem. Finally, a numerical example is given to verify the theoretical analysis.
97 citations
TL;DR: In this paper, a delayed differential equation with inertial term subject to time delay is considered and Hopf bifurcation is studied by using the normal form theory of retarded functional differential equations.
Abstract: A delayed differential equation modelling a single neuron with inertial term subject to time delay is considered in this paper. Hopf bifurcation is studied by using the normal form theory of retarded functional differential equations. When adopting a nonmonotonic activation function, chaotic behavior is observed. Phase plots, waveform plots, and power spectra are presented to confirm the chaoticity.
TL;DR: It is found that for Rossler oscillator networks, in the synchronous regime, the oscillation phases are locked, while the amplitudes vary chaotically, and the dependence of phase synchronization on the network coupling strength, the product of the shortcuts-adding probability and the number of chaotic oscillators, as well as the maximal frequency mismatch.
Abstract: Small-world networks are highly clustered networks with small average distance among the vertices. There are many natural and technological networks that present this kind of connections. We study the phase synchronization of small-world chaotic oscillator networks in this paper. We find that for Rossler oscillator networks, in the synchronous regime, the oscillation phases are locked, while the amplitudes vary chaotically. We further show the dependence of phase synchronization on the network coupling strength, the product of the shortcuts-adding probability and the number of chaotic oscillators, as well as the maximal frequency mismatch.
TL;DR: Locality pursuit embedding as discussed by the authors is a linear algorithm that arises by solving a variational problem and produces a linear embedding that respects the local geometrical structure described by the Euclidean distances.
TL;DR: It is shown that the stability of the synchronized state is independent of the network topology, that is, the stability is irrelevant to the number of vertices and the connection-adding probability in SW networks.
Abstract: In this paper, we investigate synchronization in oscillator networks with small-world (SW) interactions and coupling delays. We derive a stability criterion for the network synchronized state. We show that the stability of the synchronized state is independent of the network topology, that is, the stability of the synchronized state is irrelevant to the number of vertices and the connection-adding probability in SW networks. Numerical examples are presented to demonstrate the correctness of our theoretical result.
TL;DR: It is found that Hopf bifurcation occurs for the strong kernel of a general two-neuron model with distributed delays and a strong kernel, which means that a family of periodic solutions b ifurcates from the equilibrium when the bIfurcation parameter exceeds a critical value.
TL;DR: In all of the vibrational modes of DNA, the bases showed the most sensitive to different temperatures and there is a pronounced shift of bands at 70 degrees C, the starting point of denaturation.
TL;DR: The results show that SSPP can make the tradeoffs between resource utilization and restoration time, and based on dynamic traffic with different load, the performance of S SPP has been investigated via simulations.
Abstract: In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.
TL;DR: This paper proposes a neural network based approach to compute eigenvectors corresponding to the largest or smallest eigenvalues of any real symmetric matrix and computer simulation results show the computational capability of the network model.
Abstract: Efficient computation of eigenvectors and eigenvalues of a matrix is an important problem in engineering, especially for computing eigenvectors corresponding to largest or smallest eigenvalues of a matrix. This paper proposes a neural network based approach to compute eigenvectors corresponding to the largest or smallest eigenvalues of any real symmetric matrix. The proposed network model is described by differential equations, which is a class of continuous time recurrent neural network model. It has parallel processing ability in an asynchronous manner and can achieve high computing performance. This paper provides a clear mathematical understanding of the network dynamic behaviors relating to the computation of eigenvectors and eigenvalues. Computer simulation results show the computational capability of the network model.
TL;DR: A small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang is considered, and it is proved that Hopf bifurcation occurs.
Abstract: The notion of small-world networks, recently introduced by Watts and Strogatz, has attracted increasing interest in studying the interesting properties of complex networks. Notice that, a signal or influence travelling on a small-world network often is associated with time-delay features, which are very common in biological and physical networks. Also, the interactions within nodes in a small-world network are often nonlinear. In this paper, we consider a small-world networks model with nonlinear interactions and time delays, which was recently considered by Yang. By choosing the nonlinear interaction strength as a bifurcation parameter, we prove that Hopf bifurcation occurs. We determine the stability of the bifurcating periodic solutions and the direction of the Hopf bifurcation by applying the normal form theory and the center manifold theorem. Finally, we show a numerical example to verify the theoretical analysis.
TL;DR: A robust NLOS error mitigation algorithm based on Bootstrapping M-estimation is proposed without priorNLOS error distribution and clearly outperforms the other two.
Abstract: Mobile positioning is made difficult by nonsymmetric contamination of measured time-of-arrival (TOA) data caused by non-line-of-sight (NLOS) propagation. In this letter, a robust NLOS error mitigation algorithm based on Bootstrapping M-estimation is proposed without prior NLOS error distribution. A simulation comparison is performed in different channel environments between the proposed algorithm and two additional ones (least-square and Huber estimator). The proposed algorithm clearly outperforms the other two.
15 Jun 2004
TL;DR: This paper presents a novel distributed intrusion detection system, which uses the Dempster-Shafer's theory of evidence to fuse local information, and shows that the multi-sensor data fusion model performs much better than single sensor.
Abstract: Intrusion detection system (IDS) plays a critical role in information security because it provides the last line protection for those protected hosts or networks when intruders elude the first line. In this paper, we present a novel distributed intrusion detection system, which uses the Dempster-Shafer's theory of evidence to fuse local information. Our approach is composed of 2 layers: the lower layer consists of both host and network based sensors, which are specifically designed to collect local features and make local decisions to differentiate those easy-to-detect attacks; the upper layer is a fusion control center, it makes global decisions on those locally uncertain events by adopting Dempster's combination rule. Our approach gains the advantages of both host and network based intrusion methods, and can practice both rule-based and anomaly detection. A simulation is carried out and result shows that the multi-sensor data fusion model performs much better than single sensor.
TL;DR: Investigation of the reference electrode standardization technique (REST) for a realistic head model shows that the potential reconstruction for the realistic head models is more sensitive to noise than that for the concentric three-sphere head model, so a regularized inverse by truncated singular value decomposition was introduced.
TL;DR: The chaos synchronization in time-delayed neuron system is studied based on the method of designing the coupled system and employing Krasovskii–Lyapunov theory to search the synchronization conditions.
Abstract: It is well known that complex dynamic behaviors exist in time-delayed neural systems. Infinite positive Lyapunov exponents can be found in time-delayed chaotic systems since the dimension of such systems is infinite. However, theoretical and experimental models studied thus far are low dimensional systems with only one positive Lyapunov exponent. Consequently, messages masked by such chaotic systems are shown to be easily extracted in some cases. Therefore, communication system with a higher security level can be design by means of the time-delayed neuron systems. In this paper, we firstly investigate the dynamical behaviors of two-neuron systems with discrete delays. Then, the chaos synchronization in time-delayed neuron system is studied based on the method of designing the coupled system and employing Krasovskii–Lyapunov theory to search the synchronization conditions. Numerical results illustrate the correctness of our theoretical analyses.
TL;DR: The network is proven to be globally exponentially stable (GES) under some mild conditions and the analysis of GES extends the existing stability results for discrete-time recurrent networks.
TL;DR: By employing several Lyapunov functionals, the global exponential stability and asymptotic stability of generalized neural networks with distributed delays are investigated and milder and more general than previously known criteria are derived.
Abstract: By employing several Lyapunov functionals, the global exponential stability and asymptotic stability of generalized neural networks with distributed delays are investigated in this paper. A number of sufficient conditions for these types of stability are derived. They are milder and more general than previously known criteria, and can be applied to neural networks with constant connection weights as well as a broad range of activation functions assuming neither differentiability nor strict monotonicity. Furthermore, the results obtained for generalized neural networks with distributed delays do not assume symmetry of the connection matrix.
27 Jun 2004
TL;DR: The ADRA system is shown to result in fewer call failures than the other methods, while exhibiting many attractive features of distributed control.
Abstract: The paper describes a novel ant-based distributed route algorithm (ADRA) for ad-hoc networks. The ants move across the network between randomly chosen pairs of nodes; as they move they deposit simulated pheromones as a function of their distance from their source node, the quality of the link, the congestion encountered on their journey, the current pheromones the nodes possess and the velocity at which the nodes move. Of course, the node changes the pheromones by itself according to the quality of the link, and ages the link by pheromones evaporating. An ant selects its path at each intermediate node according to the distribution of simulated pheromones at each node. In order to accelerate the convergence rate of the congestion problem and the shortcut problem, we give the parameters different weight values to update the probability routing table. The performance of the algorithm is measured by the packet loss ratio, control overhead as well as end-to-end packet delay. The results of using the improved ant-based control protocols are compared with those achieved by using fixed shortest-path routes previously proposed for use in ad-hoc networks. The ADRA system is shown to result in fewer call failures than the other methods, while exhibiting many attractive features of distributed control.
TL;DR: Numerical simulations indicate that this network model yields three power-law distributions for the node degrees, connection weights and node strengths, respectively, which can also be reflected by this model.
Abstract: Many social, technological, biological and economical systems are best described by weighted networks, whose properties and dynamics depend not only on their structures but also on the connection weights among their nodes. However, most existing research work on complex network models are concentrated on network structures, with connection weights among their nodes being either 1 or 0. In this paper, we propose a new weighted evolving network model. Numerical simulations indicate that this network model yields three power-law distributions for the node degrees, connection weights and node strengths, respectively. Particularly, some other properties of the distributions, such as the droop-head and heavy-tail effects, can also be reflected by this model.
TL;DR: In this article, the EPR parameters of anisotropic g-factors gx, gy and gz for Cu2+ ion and hyperfine structure constants Ax, Ay and Az for 63Cu2+ and 65cu2+ isotopes in rutile (TiO2) crystal are calculated by the method of diagonalizing the full Hamiltonian matrix.
Abstract: The EPR parameters anisotropic g-factors gx, gy and gz for Cu2+ ion and hyperfine structure constants Ax, Ay and Az for 63Cu2+ and 65Cu2+ isotopes in rutile (TiO2) crystal are calculated by the method of diagonalizing the full Hamiltonian matrix. The crystal-field parameters contact with the crystal structure by the aid of the superposition model. The calculated results are in reasonable agreement with the observed values. The results are discussed. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this article, the synchronization of coupled map lattices with small-world interactions and coupling delays is studied and a stability criterion for the synchronized state is derived, and numerical examples are presented to demonstrate the correctness of the theoretical result.
Abstract: We study the synchronization of coupled map lattices with small-world interactions and coupling delays in this paper. A stability criterion for the synchronized state is derived. Numerical examples are presented to demonstrate the correctness of our theoretical result.