Showing papers by "Xidian University published in 2005"
TL;DR: Simulations and experimental results show that the proposed ADRC achieves a better position response and is robust to parameter variation and load disturbance.
Abstract: A highly robust automatic disturbances rejection controller (ADRC) is developed to implement high-precision motion control of permanent-magnet synchronous motors. The proposed ADRC consists of a tracking differentiator (TD) in the feedforward path, an extended state observer (ESO), and a nonlinear proportional derivative control in the feedback path. The TD solves the difficulties posed by low-order reference trajectories which are quantized at the sensor resolution, and the ESO provides the estimate of the unmeasured system's state and the real action of the unknown disturbances only based on a measurement output of the system. Simulations and experimental results show that the proposed ADRC achieves a better position response and is robust to parameter variation and load disturbance. Furthermore, the ADRC is designed directly in discrete time with a simple structure and fast computation, which make it widely applicable to all other types of derives.
268 citations
TL;DR: A space-time adaptive processing (STAP) approach combined with conventional SAR imaging algorithms is presented, which could be of help to overcome the existing difficulties in data processing.
Abstract: Future spaceborne synthetic aperture radar (SAR) systems will be required to produce high-resolution imagery over a wide area of surveillance. However, the minimum antenna area constraint makes it a contradiction to simultaneously obtain both unambiguous wide-area and high azimuth resolution. To overcome this limitation, a technique has been suggested that combines a broad illumination source with multiple receiving channels. Then, the coherent combination of the recorded multichannel signals will allow for the unambiguous SAR mapping of a wide ground area with fine azimuth resolution. This letter first gives an overview of current research work carried out about the generation of wide-swath and high-resolution SAR images from multichannel small spaceborne SAR systems, and then a space-time adaptive processing (STAP) approach combined with conventional SAR imaging algorithms is presented, which could be of help to overcome the existing difficulties in data processing. The main idea of the approach is to use a STAP-based method to properly overcome the aliasing affect caused by the lower pulse repetition frequency and thereby retrieve the unambiguous azimuth wide (full) spectrum signal from the received signal. Following this operation, conventional SAR data processing tools can be applied to fully focus the SAR images. The performance of the approach is also discussed in this letter. The approach has the advantages of simplicity, robustness, and high efficiency.
233 citations
TL;DR: A method for calculating the Euclidean distance in higher order spectra feature space is proposed in this paper, which avoids calculating the higher orderSpectra, effectively reducing the computation complexity and storage requirement.
Abstract: Radar high-resolution range profile (HRRP) is very sensitive to time-shift and target-aspect variation; therefore, HRRP-based radar automatic target recognition (RATR) requires efficient time-shift invariant features and robust feature templates. Although higher order spectra are a set of well-known time-shift invariant features, direct use of them (except for power spectrum) is impractical due to their complexity. A method for calculating the Euclidean distance in higher order spectra feature space is proposed in this paper, which avoids calculating the higher order spectra, effectively reducing the computation complexity and storage requirement. Moreover, according to the widely used scattering center model, theoretical analysis and experimental results in this paper show that the feature vector extracted from the average profile in a small target-aspect sector has better generalization performance than the average feature vector in the same sector when both of them are used as feature templates in HRRP-based RATR. The proposed Euclidean distance calculation method and average profile-based template database are applied to two classification algorithms [the template matching method (TMM) and the radial basis function network (RBFN)] to evaluate the recognition performances of higher order spectra features. Experimental results for measured data show that the power spectrum has the best recognition performance among higher order spectra.
215 citations
TL;DR: It is shown that the proposed method guarantees the semiglobal boundedness of all signals in the adaptive closed-loop systems.
Abstract: In this paper, an adaptive neural controller for a class of time-delay nonlinear systems with unknown nonlinearities is proposed. Based on a wavelet neural network (WNN) online approximation model, a state feedback adaptive controller is obtained by constructing a novel integral-type Lyapunov-Krasovskii functional, which also efficiently overcomes the controller singularity problem. It is shown that the proposed method guarantees the semiglobal boundedness of all signals in the adaptive closed-loop systems. An example is provided to illustrate the application of the approach.
195 citations
TL;DR: Network coding offers a new paradigm for network communications and has generated abundant research interest in information and coding theory, networking, switching, wireless communications, cryptography, computer science, operations research, and matrix theory.
Abstract: Store-and-forward had been the predominant technique for transmitting information through a network until its optimality was refuted by network coding theory. Network coding offers a new paradigm for network communications and has generated abundant research interest in information and coding theory, networking, switching, wireless communications, cryptography, computer science, operations research, and matrix theory.
186 citations
01 May 2005
TL;DR: A special nonlinear bilevel programming problem is transformed into an equivalent single objective nonlinear programming problem and a new evolutionary algorithm is proposed that can be used to handle nonlinear BLPPs with nondifferentiable leader's objective functions.
Abstract: In this paper, a special nonlinear bilevel programming problem (nonlinear BLPP) is transformed into an equivalent single objective nonlinear programming problem. To solve the equivalent problem effectively, we first construct a specific optimization problem with two objectives. By solving the specific problem, we can decrease the leader's objective value, identify the quality of any feasible solution from infeasible solutions and the quality of two feasible solutions for the equivalent single objective optimization problem, force the infeasible solutions moving toward the feasible region, and improve the feasible solutions gradually. We then propose a new constraint-handling scheme and a specific-design crossover operator. The new constraint-handling scheme can make the individuals satisfy all linear constraints exactly and the nonlinear constraints approximately. The crossover operator can generate high quality potential offspring. Based on the constraint-handling scheme and the crossover operator, we propose a new evolutionary algorithm and prove its global convergence. A distinguishing feature of the algorithm is that it can be used to handle nonlinear BLPPs with nondifferentiable leader's objective functions. Finally, simulations on 31 benchmark problems, 12 of which have nondifferentiable leader's objective functions, are made and the results demonstrate the effectiveness of the proposed algorithm.
182 citations
TL;DR: A novel timing and frequency offset estimation method is presented for orthogonal frequency division multiplexing (OFDM) systems in this paper and the accuracy of the timing offset estimator is significantly improved, and the estimate range of the frequency offset estimators is greatly enlarged.
Abstract: The synchronization method using the available constant envelop preamble is analyzed, and a new preamble weighted by pseudo-noise sequence is proposed, with which a novel timing and frequency offset estimation method is presented for orthogonal frequency division multiplexing (OFDM) systems in this paper. By the proposed method, the accuracy of the timing offset estimator is significantly improved, and the estimate range of the frequency offset estimator is greatly enlarged with no loss in accuracy. The performance of the proposed method is demonstrated by simulations.
176 citations
TL;DR: In this article, a new technique is presented from another point of view, which reconstructs a special antenna array model based on the Toeplitz matrix whose rank is only related to the DoA of signals and cannot be affected by the coherency between them.
Abstract: Conventionally, the approaches to coherent direction-of-arrival (DOA) estimation are to eliminate the rank loss of the spatial covariance matrix. In this letter, a new technique is presented from another point of view, which reconstructs a special antenna array model based on the Toeplitz matrix whose rank is only related to the DOA of signals and cannot be affected by the coherency between them. Therefore, the signal and noise subspaces can be estimated properly. In conjoint with the improved estimation of signal parameter via rotational invariance techniques (ESPRIT) algorithm, it is capable of resolving the DOAs of coherent signals as well as uncorrelated signals without peak searching. The numerical examples demonstrate its validity.
173 citations
TL;DR: In this article, an enhanced nonlinear PID (EN-PID) controller that exhibits the improved performance than the conventional linear fixed-gain PID controller is proposed, by incorporating a sector-bounded nonlinear gain in cascade with a conventional PID control architecture.
169 citations
TL;DR: A new multi-secret sharing scheme based on two variable one-way function and Hermite interpolating polynomial is presented, in which the participants' shadows remain secret and can be reused.
133 citations
08 Apr 2005
TL;DR: A preprocessing algorithm is first proposed to convert the non-coherent ISAR data into coherent data, the a keystone formatting algorithm developed for the imaging of slo ground moving targets i SAR is applied to mitigate the MTRCs to rotational motion, and a high resolutio time-frequency analysis based range-instantaneous Doppler (RID) algorithm is used to produce the focused ISAR image.
Abstract: Range-Doppler (RD) algorithms are idely used i inverse synthetic aperture radar (ISAR) imaging. I the standard RD algorithm, envelope alignment and autofocus are first applied to transform the original data into equivalent turntable target data, and the FFT is used for the image formation. Usually, the migratio through resolution cells (MTRCs) due to target rotatio is ignored. ith the improvement of resolutio or the increase of target size, MTRCs cannot be ignored and must be mitigated. For high speed moving targets, the most idely used 'stop-and-go' data model is violated. I this case, the mitigation of MTRCs becomes eve more complicated. I the paper, technical issues associated ith high resolutio ISAR imaging of high speed moving targets are addressed. A preprocessing algorithm is first proposed to convert the non-coherent ra ISAR data into coherent data, the a keystone formatting algorithm developed for the imaging of slo ground moving targets i SAR is applied to mitigate the MTRCs o ing to rotational motion, and, finally, a high resolutio time-frequency analysis based range-instantaneous Doppler (RID) algorithm is used to produce the focused ISAR image. Numerical examples are provided to illustrate the performance of the proposed approach.
TL;DR: An ID-based broadcast encryption scheme is proposed, by which a center can distribute keys over a network, so that each member of a privileged subset of users can compute a specified key.
Abstract: A broadcast encryption scheme enables a center to distribute keys and/or broadcast a message in a secure way over an insecure channel to an arbitrary subset of privileged recipients. In this paper, an ID-based broadcast encryption scheme is proposed, by which a center can distribute keys over a network, so that each member of a privileged subset of users can compute a specified key. Then a conventional private-key cryptosystem, such as DES, can be used to encrypt the subsequent broadcast with the distributed key. Because a key distribution can be done in an encrypted broadcast without any key pre-distribution, re-keying protocols for group membership operations can be simplified, a center can use the ID-based broadcast encryption scheme again to distribute a new and random session key. The ID-based broadcast encryption scheme from bilinear pairings is based on a variant of the Boneh-Franklin identity based encryption scheme.
TL;DR: A doubly local Wiener filtering algorithm, where the elliptic directional windows are used for different oriented subbands in order to estimate the signal variances of noisy wavelet coefficients, and the two procedures of localWiener filtering are performed on the noisy image.
Abstract: Local Wiener filtering in the wavelet domain is an effective image denoising method of low complexity. In this letter, we propose a doubly local Wiener filtering algorithm, where the elliptic directional windows are used for different oriented subbands in order to estimate the signal variances of noisy wavelet coefficients, and the two procedures of local Wiener filtering are performed on the noisy image. The experimental results show that the proposed algorithm improves the denoising performance significantly.
TL;DR: The proposed new simple NVE has built a solid base for high-performance control of servo systems and is model free, which has high robustness against noise and design parameters.
Abstract: Based on the fact that numerical integration can provide more stable and accurate results than numerical differentiation in the presence of noise, a constructive nonlinear velocity estimator (NVE) with simple computation is developed for high-quality instantaneous velocity estimation, based on the position measurement only. The attraction of the new velocity estimator is that it is very effective as well in the low-velocity ranges, it has high robustness against noise and design parameters, and it is easy to implement. Furthermore, the developed approach is model free. Both simulation and experimental tests have been run to verify its effectiveness and efficiency. The proposed new simple NVE has built a solid base for high-performance control of servo systems.
05 Jan 2005
TL;DR: This work proposed a novel characterization of dynamic textures that poses the problems of recognizing, and described a simple matching algorithm based on multiresolution histogram, which measure difference between two sequences.
Abstract: Dynamic textures are sequences of images of moving scenes that exhibit certain stationarity properties in time, for example, sea-waves, smoke, foliage, whirlwind etc. This work proposed a novel characterization of dynamic textures that poses the problems of recognizing. A method by spatio-temporal multiresolution histogram based on velocity and acceleration fields is presented. The spatio-temporal multiresolution histogram has many desirable properties including simple computing, spatial efficiency, robustness to noise and ability of encoding spatio-temporal dynamic information, which can reliably capture and represent the motion properties of different image sequences. Velocity and acceleration fields of different spatio-temporal resolution image sequences are accurately estimated by structure tensor method. We describe a simple matching algorithm based on multiresolution histogram, which measure difference between two sequences.
12 Oct 2005
TL;DR: In this article, an iterated extended Kalman filter (IEKF) is used to generate the proposal distribution, which integrates the latest measurements into system state transition density, so it can match the posteriori density well.
Abstract: Particle filtering shows great promise in addressing a wide variety of non-linear and /or non-Gaussian problem. A crucial issue in particle filtering is the selection of the importance proposal distribution. In this paper, the iterated extended Kalman filter (IEKF) is used to generate the proposal distribution. The proposal distribution integrates the latest measurements into system state transition density, so it can match the posteriori density well. The simulation results show that the new particle filter superiors to the standard particle filter and the other filters such as the unscented particle filter (UPF), the extended Kalman particle filter (PF-EKF), the EKF.
TL;DR: In this correspondence, the linear complexity and minimal polynomial of new generalized cyclotomic sequences of order two are determined and it is shown that these sequences also have high linear complexity.
Abstract: In this correspondence, the linear complexity and minimal polynomial of new generalized cyclotomic sequences of order two are determined. Our results show that these sequences also have high linear complexity.
TL;DR: A novel objective no-reference metric is proposed for video quality assessment of digitally coded videos containing natural scenes and experiments indicate that the objective scores obtained by the proposed metric agree well with the subjective assessment scores.
Abstract: A novel objective no-reference metric is proposed for video quality assessment of digitally coded videos containing natural scenes. Taking account of the temporal dependency between adjacent images of the videos and characteristics of the human visual system, the spatial distortion of an image is predicted using the differences between the corresponding translational regions of high spatial complexity in two adjacent images, which are weighted according to temporal activities of the video. The overall video quality is measured by pooling the spatial distortions of all images in the video. Experiments using reconstructed video sequences indicate that the objective scores obtained by the proposed metric agree well with the subjective assessment scores.
09 May 2005
TL;DR: This paper proposes an identity (ID)-based signature scheme from bilinear pairing and shows that such a scheme can be used to generate an ID-based aggregate signature and combines this with the short signature given by Boneh, Lynn and Shacham to come up with anID-based verifiably encrypted signature.
Abstract: Aggregate signatures are digital signatures that allown players to sign n different messages and all these signatures can be aggregated into a single signature This single signature enables the verifier to determine whether then players have signed the n original messages Verifiably encrypted signatures are used when Alice wants to sign a message for Bob but does not want Bob to possess her signature on the message until a later date In this paper, we first propose an identity (ID)-based signature scheme from bilinear pairing and show that such a scheme can be used to generate an ID-based aggregate signature Then, combining this ID-based signature with the short signature given by Boneh, Lynn and Shacham, we come up with an ID-based verifiably encrypted signature Due to the nice properties of the bilinear pairing, the proposed signatures are simple, efficient and have short signature size
09 Mar 2005
TL;DR: The simulation comparisons among IDCMA, the Random-Weight Genetic Algorithm and the Strength Pareto Evolutionary Algorithm show that when low-dimensional multiobjective problems are concerned, IDCma has the best performance in metrics such as Spacing and Coverage of Two Sets.
Abstract: Based on the concept of Immunodominance and Antibody Clonal Selection Theory, we propose a new artificial immune system algorithm, Immune Dominance Clonal Multiobjective Algorithm (IDCMA). The influences of main parameters are analyzed empirically. The simulation comparisons among IDCMA, the Random-Weight Genetic Algorithm and the Strength Pareto Evolutionary Algorithm show that when low-dimensional multiobjective problems are concerned, IDCMA has the best performance in metrics such as Spacing and Coverage of Two Sets.
TL;DR: In this paper, a /spl plusmn/45/spl deg/ polarization diversity antenna with wide bandwidth is presented, which has a half-power beam width of 65 degrees in the horizontal plane for use in wireless telecommunication base stations.
Abstract: A /spl plusmn/45/spl deg/ polarization diversity antenna with wide bandwidth is presented in this letter. The antenna has a half-power beam width of 65/spl deg/ in the horizontal plane for use in wireless telecommunication base stations. Especially, a folded dipole antenna with a protruding part is used as a +45/spl deg/ polarization element and the another folded dipole with a concave part is used as a -45/spl deg/ polarization element. The protruding part and the concave part of dipoles make the two folded dipoles with the same height but not touching each other. With such a cross-pair of folded dipoles, a small polarization diversity antenna is constructed. The antenna was analyzed and optimized by the high frequency structure simulation software, and a good agreement was achieved between computation and experiments on the half-power beam width in the horizontal plane.
14 Dec 2005
TL;DR: It is shown that, contrary to the authors claimed, Zhang and Kim’s scheme in ACISP 2003 is one-more forgeable, if the ROS-problem is solvable, and efficiency analyses show that the schemes can offer advantages in runtime over the schemes available.
Abstract: In this paper, we first propose an efficient provably secure identity-based signature (IBS) scheme based on bilinear pairings, then propose an efficient identity-based blind signature (IBBS) scheme based on our IBS scheme. Assuming the intractability of the Computational Diffie-Hellman Problem, our IBS scheme is unforgeable under adaptive chosen-message and ID attack. Efficiency analyses show that our schemes can offer advantages in runtime over the schemes available. Furthermore, we show that, contrary to the authors claimed, Zhang and Kim’s scheme in ACISP 2003 is one-more forgeable, if the ROS-problem is solvable.
01 Aug 2005
TL;DR: For network error-correcting codes based on network coding an explicit lower bound on the size of source alphabet is presented, deduced by a Gilbert-Varshamov greedy algorithm.
Abstract: For network error-correcting codes based on network coding an explicit lower bound on the size of source alphabet is presented. This bound is deduced by a Gilbert-Varshamov greedy algorithm. The difficulty of constructing good error-correcting codes for networks is considered and ways of constructing good codes for small-scale networks are dealt with in detail.
25 Mar 2005
TL;DR: In this paper a new algebraic method is proposed to illustrate the reason why AES S-box algebraic expression is very simple, which corrects all the available inaccurate illustrations.
Abstract: It is well known that the algebraic expression of the advanced encryption standard (AES) Rijndael S-box is very simple and only 9 terms are involved. In this paper a new algebraic method is proposed to illustrate the reason why AES S-box algebraic expression is very simple, which corrects all the available inaccurate illustrations. An improved AES S-box is also presented to improve the complexity of AES S-box algebraic expression with terms increasing from 9 to 255 and algebraic degree invariable. The improved AES S-box also has good properties of Boolean functions in SAC and balance, and is capable of attacking against differential cryptanalysis with high reliable security.
16 May 2005
TL;DR: In this paper, a semi-analytic finite element method was proposed to solve the open boundary axisymmetric electrostatic field problems, which is applied to computing the potential distribution of the high voltage porcelain metal oxide arrester (MOA).
Abstract: This paper proposes a semi-analytic finite element method to treat the open boundary axisymmetric electrostatic field problems. The method is applied to computing the potential distribution of the high voltage porcelain metal oxide arrester (MOA). The numerical example shows a good agreement between the calculated and measured results.
TL;DR: The two-dimensional scattering of a Gaussian beam by a periodic array of circular cylinders is studied using the plane-wave spectrum technique based on Fourier optics.
Abstract: The two-dimensional scattering of a Gaussian beam by a periodic array of circular cylinders is studied. The incident Gaussian beam is expressed as a superposition of plane waves of different amplitudes and different incident angles, using the plane-wave spectrum technique based on Fourier optics. For each plane wave, the scattered field is calculated with the T-matrix of an isolated circular cylinder and its lattice sums characterizing a periodic arrangement of the circular cylinders. The circular cylinders may be perfect conductors, dielectric or gyrotropic cylinders, as long as their T-matrices are known.
TL;DR: Computer simulations and analysis in this paper demonstrates that, especially when the HPA is working near or in the saturation region, a predistorter ceases to be in effect.
Abstract: There have been many papers concerning about the peak to average power ratio (PAPR) reduction and high power amplifier (HPA) linearization techniques for wireless OFDM communication systems. Few papers, however, make deep analysis on the relation between these two techniques. Based on Saleh's memoryless traveling wave tube amplifier (TWTA) model, computer simulations and analysis in this paper demonstrates that, especially when the HPA is working near or in the saturation region, a predistorter ceases to be in effect. In such cases, PAPR reduction techniques may be resorted to help to improve the adjacent channel interference (ACI), BER performances and HPA efficiency.
31 Aug 2005
TL;DR: A novel feature weighted fuzzy clustering algorithm is proposed in this paper, in which the ReliefF algorithm is used to assign the weights for every feature.
Abstract: In the field of cluster analysis, the fuzzy k-means, k-modes and k-prototypes algorithms were designed for numerical, categorical and mixed data sets respectively. However, all the above algorithms assume that each feature of the samples plays an uniform contribution for cluster analysis. To consider the particular contributions of different features, a novel feature weighted fuzzy clustering algorithm is proposed in this paper, in which the ReliefF algorithm is used to assign the weights for every feature. By weighting the features of samples, the above three clustering algorithms can be unified, and better classification results can be also achieved. The experimental results with various real data sets illustrate the effectiveness of the proposed algorithm.
TL;DR: A weighted difference index is presented to calculate the distance between vague values, by means of which the distance of alternatives to VPIS and VNIS can be calculated and the relative closeness values of various alternatives to the positive-ideal solution are ranked to determine the best alternative.
Abstract: This paper extends the TOPSIS to fuzzy MCDM based on vague set theory, where the characteristics of the alternatives are represented by vague sets. A novel score function is proposed in order to determine the vague positive-ideal solution (VPIS) and vague negative-ideal solution (VNIS). We present a weighted difference index to calculate the distance between vague values, by means of which the distance of alternatives to VPIS and VNIS can be calculated. Finally, the relative closeness values of various alternatives to the positive-ideal solution are ranked to determine the best alternative. An example is shown to illustrate the procedure of the proposed method at the end of this paper.
TL;DR: It is shown that this protocol is insecure because a cheater can gain all the secret bits before sharing, while introducing one data bit error at most in the whole communication, which makes the cheater avoid the detection by the communication parities.
Abstract: In a recent paper [S. Bagherinezhad and V. Karimipour, Phys. Rev. A 67, 044302 (2003)], a quantum secret sharing protocol based on reusable Greenberger-Horne-Zeilinger states was proposed. However, in this Comment, it is shown that this protocol is insecure if Eve employs a special strategy to attack.