scispace - formally typeset
Search or ask a question

Showing papers by "Xidian University published in 2009"


Journal ArticleDOI
TL;DR: A novel image fusion algorithm based on the nonsubsampled contourlet transform (NSCT) is proposed, aiming at solving the fusion problem of multifocus images, and significantly outperforms the traditional discrete wavelets transform-based and the discrete wavelet frame transform- based image fusion methods.

593 citations


Journal ArticleDOI
TL;DR: An efficient quantum private comparison protocol for comparing information of equality with the help of a third party (TP) is proposed, which can ensure fairness, efficiency and security.
Abstract: Following some ideas of the quantum secret sharing (QSS) protocol (2008, Phys. Lett. A 372, 1957), we propose an efficient quantum private comparison (QPC) protocol for comparing information of equality with the help of a third party (TP). The protocol can ensure fairness, efficiency and security. The protocol is fair, which means that one party knows the sound result of the comparison if and only if the other one knows the result. The protocol is efficient with the help of the TP for calculating. However, the TP cannot learn any information about the players' respective private inputs and even about the comparison result and cannot collude with any player. The protocol is secure for the two players, that is, any information about their respective secret inputs will not leak except the final computation result. A precise proof of security of the protocol is presented. Applications of this protocol may include private bidding and auctions, secret ballot elections, commercial business, identification in a number of scenarios and so on.

285 citations


Journal ArticleDOI
TL;DR: A novel framework for IQA to mimic the human visual system (HVS) by incorporating the merits from multiscale geometric analysis (MGA), contrast sensitivity function (CSF), and the Weber's law of just noticeable difference (JND) is developed.
Abstract: Reduced-reference (RR) image quality assessment (IQA) has been recognized as an effective and efficient way to predict the visual quality of distorted images. The current standard is the wavelet-domain natural image statistics model (WNISM), which applies the Kullback-Leibler divergence between the marginal distributions of wavelet coefficients of the reference and distorted images to measure the image distortion. However, WNISM fails to consider the statistical correlations of wavelet coefficients in different subbands and the visual response characteristics of the mammalian cortical simple cells. In addition, wavelet transforms are optimal greedy approximations to extract singularity structures, so they fail to explicitly extract the image geometric information, e.g., lines and curves. Finally, wavelet coefficients are dense for smooth image edge contours. In this paper, to target the aforementioned problems in IQA, we develop a novel framework for IQA to mimic the human visual system (HVS) by incorporating the merits from multiscale geometric analysis (MGA), contrast sensitivity function (CSF), and the Weber's law of just noticeable difference (JND). In the proposed framework, MGA is utilized to decompose images and then extract features to mimic the multichannel structure of HVS. Additionally, MGA offers a series of transforms including wavelet, curvelet, bandelet, contourlet, wavelet-based contourlet transform (WBCT), and hybrid wavelets and directional filter banks (HWD), and different transforms capture different types of image geometric information. CSF is applied to weight coefficients obtained by MGA to simulate the appearance of images to observers by taking into account many of the nonlinearities inherent in HVS. JND is finally introduced to produce a noticeable variation in sensory experience. Thorough empirical studies are carried out upon the LIVE database against subjective mean opinion score (MOS) and demonstrate that 1) the proposed framework has good consistency with subjective perception values and the objective assessment results can well reflect the visual quality of images, 2) different transforms in MGA under the new framework perform better than the standard WNISM and some of them even perform better than the standard full-reference IQA model, i.e., the mean structural similarity index, and 3) HWD performs best among all transforms in MGA under the framework.

251 citations


Journal ArticleDOI
TL;DR: A novel 3-D MOCO method is proposed to extract necessary motion parameters from radar raw data, based on an instantaneous Doppler rate estimate, suitable for low- or medium-altitude UAV SAR systems equipped with a low-accuracy inertial navigation system.
Abstract: Unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) is very important for battlefield awareness. For SAR systems mounted on a UAV, the motion errors can be considerably high due to atmospheric turbulence and aircraft properties, such as its small size, which makes motion compensation (MOCO) in UAV SAR more urgent than other SAR systems. In this paper, based on 3-D motion error analysis, a novel 3-D MOCO method is proposed. The main idea is to extract necessary motion parameters, i.e., forward velocity and displacement in line-of-sight direction, from radar raw data, based on an instantaneous Doppler rate estimate. Experimental results show that the proposed method is suitable for low- or medium-altitude UAV SAR systems equipped with a low-accuracy inertial navigation system.

241 citations


Journal ArticleDOI
TL;DR: A conceptive upper bound of the cross-range resolution is presented based on the CS theory and a framework of high-resolution inverse synthetic aperture radar imaging with limited measured data is presented.
Abstract: Recent theory of compressed sampling (CS) suggests that exact recovery of an unknown sparse signal with overwhelming probability can be achieved from very limited number of samples. In this letter, we adapt this idea and present a framework of high-resolution inverse synthetic aperture radar imaging with limited measured data. During the framework, we mathematically convert the imaging into a problem of signal reconstruction with orthogonal basis; hence, a conceptive upper bound of the cross-range resolution is presented based on the CS theory. Real data results show that the CS imaging approach outperforms the conventional range-Doppler one in resolution.

237 citations


Journal ArticleDOI
Changhong Chen1, Jimin Liang1, Heng Zhao1, Haihong Hu1, Jie Tian1 
TL;DR: Experimental results show the superiority of FDEI representation over binary silhouettes and some other algorithms when occlusion or body portion lost appears in the gait sequences.

233 citations


Journal ArticleDOI
TL;DR: This paper considers the maximum likelihood formulation of this target localization problem and provides efficient convex relaxations for this nonconvex optimization problem and proposes a formulation for robust target localization in the presence of sensor location errors.
Abstract: We consider the problem of target localization by a network of passive sensors. When an unknown target emits an acoustic or a radio signal, its position can be localized with multiple sensors using the time difference of arrival (TDOA) information. In this paper, we consider the maximum likelihood formulation of this target localization problem and provide efficient convex relaxations for this nonconvex optimization problem. We also propose a formulation for robust target localization in the presence of sensor location errors. Two Cramer-Rao bounds are derived corresponding to situations with and without sensor node location errors. Simulation results confirm the efficiency and superior performance of the convex relaxation approach as compared to the existing least squares based approach when large sensor node location errors are present.

226 citations


Journal ArticleDOI
TL;DR: A joint direction of arrivals (DOAs) and direction of departures (DODs) estimation algorithm for bistatic multiple-input multiple-output (MIMO) radar via ESPRIT by means of the rotational factor produced by multi-transmitter is presented.

225 citations


Journal ArticleDOI
TL;DR: A novel object tracking algorithm is presented in this paper by using the joint color-texture histogram to represent a target and then applying it to the mean shift framework, which improves greatly the tracking accuracy and efficiency with fewer mean shift iterations than standard mean shift tracking.
Abstract: A novel object tracking algorithm is presented in this paper by using the joint color-texture histogram to represent a target and then applying it to the mean shift framework. Apart from the conventional color histogram features, the texture features of the object are also extracted by using the local binary pattern (LBP) technique to represent the object. The major uniform LBP patterns are exploited to form a mask for joint color-texture feature selection. Compared with the traditional color histogram based algorithms that use the whole target region for tracking, the proposed algorithm extracts effectively the edge and corner features in the target region, which characterize better and represent more robustly the target. The experimental results validate that the proposed method improves greatly the tracking accuracy and efficiency with fewer mean shift iterations than standard mean shift tracking. It can robustly track the target under complex scenes, such as similar target and background appearance, o...

207 citations


Proceedings ArticleDOI
24 Apr 2009
TL;DR: A group of strategies with multi-stage linearly-decreasing inertia weight (MLDW) is proposed in order to get better balance between the global and local search.
Abstract: The inertia weight is often used to control the global exploration and local exploitation abilities of particle swarm optimizers (PSO). In this paper, a group of strategies with multi-stage linearly-decreasing inertia weight (MLDW) is proposed in order to get better balance between the global and local search. Six most commonly used benchmarks are used to evaluate the MLDW strategies on the performance of PSOs. The results suggest that the PSO with W5 strategy is a good choice for solving unimodal problems due to its fast convergence speed, and the CLPSO with W5 strategy is more suitable for solving multimodal problems. Also, W5-CLPSO can be used as a robust algorithm because it is not sensitive to the complexity of problems for solving.

185 citations


Journal ArticleDOI
TL;DR: In this article, a spade-shaped ultrawideband (UWB) printed planar monopole antenna with triple band-notched characteristics is proposed by employing a hook-shaped defected ground structure (DGS) in each side of the ground plane, embedding an Omega-shaped slot on the radiating patch as well as adding a semi-octagon-shaped resonant ring on the back side of antenna, triple notched frequency bands are achieved.
Abstract: A novel spade-shaped ultrawideband (UWB) printed planar monopole antenna with triple band-notched characteristics is proposed. By employing a hook-shaped defected ground structure (DGS) in each side of the ground plane, embedding an Omega-shaped slot on the radiating patch as well as adding a semi-octagon-shaped resonant ring on the back side of the antenna, triple notched frequency bands are achieved. The proposed antenna has been successfully simulated, fabricated, and measured. Effects of the key parameters on the frequency ranges of the notched bands are also investigated. The measured impedance bandwidth defined by VS WR < 2 of 10.1 GHz (2.9-13 GHz), with the triple notched bands of 3.3-3.9, 5.2-5.35, and 5.8-6.0 GHz, is obtained. Measured group delay and transmission characteristics indicate that the antenna has good transient response. Furthermore, the proposed antenna shows the merit of insensitivity to both finite ground size and fabrication tolerances.

Journal ArticleDOI
TL;DR: The results suggest that GTA is a useful tool in defining dysregulated neural networks even during rest, and may contribute to decrease self-control, impaired inhibitory function as well deficits in stress regulation in chronic heroin users.

Journal ArticleDOI
TL;DR: This paper proposes a content-based watermarking scheme that combines the invariant feature extraction with watermark embedding by using Tchebichef moments to realize the robustness to common image processing operations and the blind detection.

Journal ArticleDOI
TL;DR: A visual cluster validation tool, the Cluster Validity Analysis Platform (CVAP), to facilitate cluster validation and can help users accomplish their clustering tasks faster and easier and help achieve good clustering quality when there is little prior knowledge about the cluster structure of a data set.
Abstract: Evaluation of clustering results (or cluster validation) is an important and necessary step in cluster analysis, but it is often time-consuming and complicated work. We present a visual cluster validation tool, the Cluster Validity Analysis Platform (CVAP), to facilitate cluster validation. The CVAP provides necessary methods (e.g., many validity indices, several clustering algorithms and procedures) and an analysis environment for clustering, evaluation of clustering results, estimation of the number of clusters, and performance comparison among different clustering algorithms. It can help users accomplish their clustering tasks faster and easier and help achieve good clustering quality when there is little prior knowledge about the cluster structure of a data set.

Proceedings ArticleDOI
07 Nov 2009
TL;DR: Experimental results demonstrated that the proposed NLBP can reconstruct faithfully the HR images with sharp edges and texture structures and outperforms the state-of-the-art methods in both PSNR and visual perception.
Abstract: This paper presents a novel non-local iterative back-projection (NLIBP) algorithm for image enlargement. The iterative back-projection (IBP) technique iteratively reconstructs a high resolution (HR) image from its blurred and downsampled low resolution (LR) counterpart. However, the conventional IBP methods often produce many “jaggy” and “ringing” artifacts because the reconstruction errors are back projected into the reconstructed image isotropically and locally. In natural images, usually there exist many non-local redundancies which can be exploited to improve the image reconstruction quality. Therefore, we propose to incorporate adaptively the non-local information into the IBP process so that the reconstruction errors can be reduced. Experimental results demonstrated that the proposed NLBP can reconstruct faithfully the HR images with sharp edges and texture structures. It outperforms the state-of-the-art methods in both PSNR and visual perception.

Journal ArticleDOI
Weisheng Chen1
TL;DR: In this article, the adaptive neural network tracking control problem for a class of strict-feedback systems with unknown non-linearly parameterised and time-varying disturbed function of known periods is addressed.
Abstract: This paper addresses the adaptive neural network tracking control problem for a class of strict-feedback systems with unknown non-linearly parameterised and time-varying disturbed function of known periods. Radial basis function neural network and Fourier series expansion are combined into a new function approximator to model each suitable disturbed function in systems. Dynamic surface control approach is used to solve the problem of ‘explosion of complexity’ in backstepping design procedure. The uniform boundedness of all closed-loop signals is guaranteed. The tracking error is proved to converge to a small residual set around the origin. A simulation example is provided to illustrate the effectiveness of the control scheme designed.

Journal ArticleDOI
TL;DR: A two-party quantum private comparison protocol using single photons, in which two distrustful parties can compare whether their secrets are equal with the help of a third party (TP), which will not be leaked out even with a compromised TP.
Abstract: We propose a two-party quantum private comparison protocol using single photons, in which two distrustful parties can compare whether their secrets are equal with the help of a third party (TP). Any information about the values of their respective secrets will not be leaked out even with a compromised TP. Security is also discussed.

Journal ArticleDOI
TL;DR: In this paper, a novel bionic ultrawideband (UWB) antenna is proposed by use of a model of insect tentacle, and its radiation characteristics are simulated and experimentally verified.
Abstract: Bionics principle is applied to antenna radar cross section (RCS) reduction in this letter for the first time. To authenticate the method, a novel bionic ultrawideband (UWB) antenna is proposed by use of a model of insect tentacle. Its UWB-related radiation characteristics are simulated and experimentally verified. Monostatic RCS of an insect tentacle antenna (ITA) terminated with three different loads are studied and compared with that of a common printed circular-disc monopole antenna (PCDMA). The results show that compared to the reference antenna, the novel bionic antenna has lower RCS and favorable radiation performances. Hence, applying bionics principle to antenna RCS reduction is feasible, which will serve as a good candidate for the future design of antennas with a requirement of RCS control.

Journal ArticleDOI
TL;DR: A new authenticated key exchange protocol NAKE is proposed, which can solve the existing problems in the original proposal and is probably secure in CK security model, thus it inherits the corresponding security attributes in CKSecurity model.

Journal ArticleDOI
TL;DR: The Lamina Emergent Torsional Joint (LET) as mentioned in this paper is a compliant joint suitable for applications where large angular rotation is desired, but high off-axis stiffness is not as critical.

Journal ArticleDOI
Li Lin1, Ji Hongbing1
TL;DR: In this paper, an improved EMD method for signal feature extraction is proposed, where an inverse EMD filter scheme is used to obtain the optimal envelopes mean and a new sifting stop criterion is proposed to guarantee the orthogonality of the sifting results.

Journal ArticleDOI
TL;DR: It is suggested that acupuncture may not only enhance the dichotomy of the anticorrelated resting networks, but also modulate a larger spatio-temporal extent of spontaneous activities in the salient interoceptive-autonomic network, contributing to potential actions in the endogenous pain-modulation circuits and homeostatic control mechanisms.

Journal ArticleDOI
Chao Deng1, Y. Xie1, Ping Li1
TL;DR: In this paper, a coplanar waveguide (CPW)-fed monopole antenna is proposed, which is composed of a rectangular monopole patch notched at the bottom, a T-shaped CPW ground in the notch, and a tapered CWS ground out of the notch.
Abstract: A coplanar waveguide (CPW)-fed monopole antenna is proposed, which is composed of a rectangular monopole patch notched at the bottom, a T-shaped CPW ground in the notch, and a tapered CPW ground out of the notch. The simulated and experimental results show that the antenna achieves a fractional impedance bandwidth of 164% for S11 ? -10 dB, which is about 2.3 times of the conventional one. The parametric studies and measured radiation characteristics are presented. The results show that the antenna exhibits good characteristics and is suitable for portable mobile ultrawideband (UWB) applications.

Journal ArticleDOI
TL;DR: It is found that the activity patterns during rest were associated with the stimulus types and that the resting activities might be even higher than that of stimulation phases and may pose great implications for the design and interpretation of a range of acupuncture neuroimaging studies.
Abstract: When studying the neural responses to acupuncture with a block-designed paradigm, its temporal dynamics predicted by the general linear model (GLM) conforms to typical "on-off" variations during a limited period of the experiment manipulation. Despite a lack of direct evidence associating its psychophysiological response, numerous clinical reports suggest that acupuncture can provide pain relief beyond a needling session. Therefore, a typical GLM analysis may be insensitive or inappropriate for identifying altered neural responses resulting from acupuncture. We developed a new approach to investigate the dynamics underlying sustained effects of acupuncture. Specifically, we designed two separate models to evaluate the baseline activities (prior to stimulation) and neural activities in sequential epochs, using three block-designed functional runs: acupuncture at acupoint ST36, nonmeridian point (NMP) stimulation, and a visual task. We found that the activity patterns during rest were associated with the stimulus types and that the resting activities might be even higher than that of stimulation phases. Such effects of the elevated activity during rest may reduce or eliminate the activity during stimulus conditions or even reverse the sign of brain activation using conventional GLM analysis. Moreover, such sustained responses, followed by acupuncture at ST36 and NMP, exhibited distinct patterns in wide brain structures, particularly in the limbic system and brainstem. These findings may pose great implications for the design and interpretation of a range of acupuncture neuroimaging studies.

Journal ArticleDOI
TL;DR: In this article, the problem of finite-time stability and stabilization of nonlinear Markovian switching stochastic systems which exist at the switching instants is addressed using multiple Lyapunov function theory.

Proceedings ArticleDOI
14 Jun 2009
TL;DR: The results show the unslotted mode has better performance than the slotted one in terms of throughput and latency but with the cost of much power consumption.
Abstract: IEEE 802.15.4 is a current major technology for low-rate low-power wireless networks. To study the applicability of IEEE 802.15.4 over a wireless body area network (WBAN), in this paper we evaluate its three different access schemes' performance through several metrics. Considering the coexistence of contention access period (CAP) and contention-free period (CFP), we also study the mutual influences of these two traffics. The results show the unslotted mode has better performance than the slotted one in terms of throughput and latency but with the cost of much power consumption. In addition, the guaranteed time slot (GTS) in CFP can not guarantee the successful transmission of the CFP frames without sufficient GTS allocation. Finally, we give the suggestions for the novel medium access control (MAC) design for a WBAN.

Journal ArticleDOI
TL;DR: A modified-Wigner-Ville distribution (referred to as M-WVD) approach is proposed, which is based on a scale transform in the time-frequency distribution plane and can effectively suppress the troublesome cross-term interference associated with WVD via coherent integration.
Abstract: Inverse synthetic aperture radar (ISAR) imaging of air, space or ship targets with complex motion has attracted the attention of many researchers in the past decade. Complex motion of targets induce cross-range scatterer-variant quadratic phase terms, which will degrade the cross-range resolution and affect focusing quality. A new algorithm is proposed for the ISAR imaging of complex moving targets. First, conventional range alignment, phase compensation and range compression are performed over the raw phase history data such that each range bin can be modelled as the sum of several linear frequency modulation or chirp signals. Secondly, a modified-Wigner-Ville distribution (referred to as M-WVD) approach is proposed, which is based on a scale transform in the time-frequency distribution plane and can effectively suppress the troublesome cross-term interference associated with WVD via coherent integration. Finally, the azimuth ISAR image can be obtained via a simple maximisation projection from the two-dimensional accumulated plot to the azimuth dimension. Compared with existing WVD-based ISAR imaging algorithms, the proposed method has the following features: better cross-term interference reduction achieved at no resolution loss, computationally more efficient with no expensive two-dimensional parameter search, and higher signal processing gain because of coherent integration during the whole imaging time. Both numerical and experimental results are provided to demonstrate the performance of the proposed method.

Journal ArticleDOI
TL;DR: A synthesis method based on differential evolution algorithm is proposed for conformal antenna arrays in the presence of platform that reduces the storage and computation time needed by the method of moments.
Abstract: A synthesis method based on differential evolution algorithm is proposed for conformal antenna arrays in the presence of platform. With the desired phase weights determined by the scan angle and array geometry, the amplitude weights of elements are optimized by differential evolution algorithm to drive down the side-lobes. Both the effect of platform on radiation pattern of conformal array and the mutual coupling between the elements are taken into account by calculating the antenna array and platform simultaneously using the method of moment. Application of adaptive integral method reduces the storage and computation time needed by the method of moments.

Journal ArticleDOI
TL;DR: In this paper, a broadband planar reflectarray with parasitic dipoles is presented for wireless communication applications, which can effectively extend the reflection phase range beyond 360°, which overcomes the problem of an inadequate phase range when using thicker substrates for a wider operational bandwidth.
Abstract: A novel broadband planar reflectarray with parasitic dipoles is presented for wireless communication applications. A unit cell of the microstrip reflectarray consists of a printed main dipole with a pair of parasitic dipoles. The introduction of parasitic dipoles can effectively extend the reflection phase range beyond 360°, which overcomes the problem of an inadequate phase range when using thicker substrates for a wider operational bandwidth. The parasitic dipole reflectarrray (PDR) is applied to a wideband CDMA (WCDMA) system to eliminate blind spots in communication between the base station and mobile users. A practical link budget analysis demonstrates the effectiveness of the proposed planar reflectarray.

Journal ArticleDOI
Feng Zhou1, Mengdao Xing1, Xueru Bai1, Guang-Cai Sun1, Zheng Bao1 
TL;DR: A new NBI suppression algorithm using the complex empirical mode decomposition (CEMD) method, which is robust to time-varying NBI and well-focused SAR imagery can be obtained from the separated target echoes using traditional SAR imaging algorithms.
Abstract: Narrow-band interference (NBI) is a common interference source in synthetic aperture radar (SAR) imaging. Its existence will degrade the imaging quality greatly. Based on detailed analysis on the characteristics of NBI, this letter proposes a new NBI suppression algorithm using the complex empirical mode decomposition (CEMD) method. In this algorithm, echoes that include NBI are recognized in the time domain first. Then, these echoes are decomposed into a number of intrinsic mode functions (IMFs) via the CEMD. After that, IMFs that correspond to NBI are subtracted from the echoes by thresholding. Finally, well-focused SAR imagery can be obtained from the separated target echoes using traditional SAR imaging algorithms. The effective data loss in this algorithm is smaller than other NBI suppression approaches. In addition, this algorithm is robust to time-varying NBI. Imaging results of measured data have proved the validity of this algorithm.