Xi'an, China
Xi'an, China

Xidian University, also known as University of Electronic Science and Technology at Xi'an, is a university located in Xi'an, Shaanxi, People's Republic of China. The university is regarded as having strong science and engineering programs, and is particularly famous in Information Technology related disciplines in China. Wikipedia.


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Liu P.,Xidian University | Liu J.,Xidian University
Physica A: Statistical Mechanics and its Applications | Year: 2017

Recently, coevolution between strategy and network structure has been established as a rule to resolve social dilemmas and reach optimal situations for cooperation. Many follow-up researches have focused on studying how coevolution helps networks reorganize to deter the defectors and many coevolution methods have been proposed. However, the robustness of the coevolution rules against attacks have not been studied much. Since attacks may directly influence the original evolutionary process of cooperation, the robustness should be an important index while evaluating the quality of a coevolution method. In this paper, we focus on investigating the robustness of an elementary coevolution method in resolving the prisoner's dilemma game upon the interdependent networks. Three different types of time-independent attacks, named as edge attacks, instigation attacks and node attacks have been employed to test its robustness. Through analyzing the simulation results obtained, we find this coevolution method is relatively robust against the edge attack and the node attack as it successfully maintains cooperation in the population over the entire attack range. However, when the instigation probability of the attacked individuals is large or the attack range of instigation attack is wide enough, coevolutionary rule finally fails in maintaining cooperation in the population. © 2017 Elsevier B.V.


Zhang Q.,Xidian University | Liang Y.,Xidian University
Journal of Advanced Oxidation Technologies | Year: 2017

Reduction of CO2 into useful fuels is regarded as a new way to deal with increasing CO2 emissions and its bad effects on climate. In this report, simple electrochemical oxidation-reduction method has been utilized to prepare Cu2O/polyaniline (PANI)/stainless steel composite electrode, which was identified as a contributor for CO2 reduction in an aqueous solution. X-ray diffraction (XRD), transmission electron microscope (TEM) and cyclic voltammetry technique were carried out to characterize the as-obtained electrode. As-synthesized composite electrode exhibited excellent electrocatalytic activity. The production of formaldehyde that comes from the reduction of CO2 using Cu2O/PANI/stainless steel based electrode (Cu2O/PANI/stainless steel) in 0.1mol/L sodium sulfate solution is 0.505 μmol·L-1·h-1 approximately. © 2017 by Walter De Gruyter GmbH 2017.


Zhang Y.,Xidian University | Ji H.,Xidian University | Hu Q.,Xidian University
Information Fusion | Year: 2017

This paper presents a box-particle implementation of the standard probability hypothesis density (PHD) filter for extended target tracking, called the extended target box-particle PHD (ET-Box-PHD) filter. The proposed filter can dynamically track multiple extended targets and estimate the unknown number of extended targets, in the presence of clutter measurements, false alarms and missed detections, where the extended targets are described as a Poisson model developed by Gilholm et al. To get the PHD recursion of the ET-Box-PHD filter, a suitable cell likelihood function for one given reliable partition is derived, and the main filter steps are presented along with the necessary box manipulations and approximations. The capabilities and limitations of the proposed ET-Box-PHD filter are illustrated both in linear simulation examples and in nonlinear ones. The simulation results show that the proposed ET-Box-PHD filter can effectively avoid the high number of particles and obviously reduce computational burden, compared to a particle implementation of the standard PHD filter for extended target tracking. © 2016 Elsevier B.V.


Liu L.,Xidian University | Yang Y.-T.,Xidian University
Journal of Advanced Oxidation Technologies | Year: 2017

Current conduction mechanisms of SiC metal-oxide-semiconductor (MOS) capacitors on n-type 4H-SiC with or without NO annealing have been investigated in this work. It has been revealed that Fowler-Nordheim (FN) tunneling is the dominating current conduction mechanism in high electrical fields, with barrier height of 2.67 and 2.54 eV respectively for samples with NO and without NO annealing. A higher barrier height for NO-annealed sample indicates the effect of N element on the SiC/SiO2 interface quality. In the intermediate oxide field, instead of trap-assisted tunneling (TAT), Poole-Frenkel (PF) emission play the key role in this region. A combination of C-V characteristics also show us the advantages of NO annealing on the SiC/SiO2 characteristics. © 2017 by Walter De Gruyter GmbH 2017.


Wang X.,Xidian University | Jung C.,Xidian University
VCIP 2016 - 30th Anniversary of Visual Communication and Image Processing | Year: 2016

Most existing contrast enhancement methods obtain the maximum clipping point by iterations under a given PSNR/SSIM value, and perform backlight scaling to maintain image quality. However, they need high computational complexity to determine the optimal clipping point and often cause over-saturation in images. In this paper, we propose backlight scaled contrast enhancement for LCDs without given PSNR/SSIM values using image key-based compression. We automatically determine the optimal clipping point for backlight scaling using image decomposition and image key-based compression. We first decompose an image into base and detail layers using bilateral filtering, and then determine the maximum clipping point using image key-based compression. Finally, we perform image compensation from the clipping point using gamma correction. Extensive experiments on various test images demonstrate that the proposed method minimizes over-saturation effects and enhances overall image quality in backlight scaling while significantly reducing power consumption. © 2016 IEEE.


Chang Y.,Xidian University | Jung C.,Xidian University
VCIP 2016 - 30th Anniversary of Visual Communication and Image Processing | Year: 2016

We propose perceptual contrast enhancement of dark images based on textural coefficients. The textural coefficient indicates textural degree of intensity and adaptively stretches the dynamic range in an image. First, we calculate gray level difference between a central pixel and its adjacent ones. Because some differences are obviously noticeable by human eyes, we only use unnoticeable differences to obtain the textural coefficient. We apply the just noticeable difference (JND) of the human visual system (HVS) to obtain the proper threshold. Then, we apply a Gaussian kernel to texture coefficients for avoiding excessive differences between adjacent ones. Finally, we perform optimal contrast tone mapping to obtain a mapping function. Experimental results show that the proposed method successfully enhances dark regions while avoiding over-enhancement in bright regions without halo artifact and tone distortion. © 2016 IEEE.


Wang L.,Xidian University | Jung C.,Xidian University
VCIP 2016 - 30th Anniversary of Visual Communication and Image Processing | Year: 2016

In this paper, we propose tone-preserving contrast enhancement in images using rational tone mapping and constrained optimization. We first perform spike-removed histogram equalization (SRHE) for contrast enhancement to avoid over-enhancement caused by the conventional HE. We conduct rational tone mapping (RTM) with low-complexity to preserve the original tone continuity. Then, we formulate a constrained optimization problem consisting of the contrast enhancement and tone-preserving terms. By minimizing the objective function, we find the best trade-off between the two conflicting terms. Experimental results demonstrate that the proposed method enhances contrast in images while successfully preserving details, and outperforms state-of-the-art ones in both subjective and objective assessments. © 2016 IEEE.


Zhang Z.,Xidian University | Jung C.,Xidian University
VCIP 2016 - 30th Anniversary of Visual Communication and Image Processing | Year: 2016

The weighted least squares (WLS) filter is a well-known edge preserving smoothing technique, but its weights highly depend on the image gradients. Thus, it is hard to smooth local textures with large gradients by WLS filter. In this paper, we propose a structure tensor-based WLS (ST-WLS) filter to enhance the smoothing ability of WLS filter while successfully keeping object boundaries. We introduce structure tensor into WLS filter to extract local structures in an image and use them to guide the smoothing process. Specifically, we use structure tensor to measure isotropy of pixels. Then, we calculate the smoothing weights for pixels based on both their isotropy and gradients. Experimental results demonstrate that ST-WLS filter has strong ability of smoothing textures, especially for isotropic textures, while preserving boundaries and structures of objects. © 2016 IEEE.


Lu X.-Z.,Xidian University
Lecture Notes in Electrical Engineering | Year: 2017

The Bionic Electronics industry often requires that flexible artificial skin should have human skin-like multi-sensory functions. However, present sensors are difficult to achieve tactile and pressure sensory functions simultaneously due to the trade-off between measurement range and measurement precision. In order to deal with this problem, this paper presents a flexible tactile-pressure sensor based on bionic structure. The bionic structure combines several sensors to simulate different types of pressure stimulation receptors of the human skin. The upper sensors have high measurement accuracy to achieve the tactile sensory function. The lower sensor has a wide measurement range to achieve pressure sensory function. These two measurement ranges are able to realize multi-scale stress measurement of external pressure stimulation. The sensor, in turn, is able to perform the tactile and pressure sensory functions simultaneously. © Zhejiang University Press and Springer Science+Business Media Singapore 2017.


Li F.,Xidian University | Feng G.,Xi'an Jiaotong University
Journal of Computational and Theoretical Nanoscience | Year: 2016

Through establishing group decision-making hierarchical structured model, this paper studies the obstacles in the development of cultural industry, and analyzes the main reasons for the existence of obstacles, and obtains methods to eliminate the obstacles in the development of cultural industry, namely, to reasonably construct development and management plan of cultural industry, to build sound cultural industry chain around a special core point, to establish a complete financial investment system through competition, that the government should strengthen the intervention and develop relevant policies and to pointedly cultivate relevant talents. And then through mechanism analysis method, this paper identifies the macro correlation between financial investment and cultural industry structure. © Copyright 2016 American Scientific Publishers All rights reserved.


Tian W.,Xidian University | Li W.,Xidian University
Journal of Computational and Theoretical Nanoscience | Year: 2016

The vibrational properties of nanoelectromechanical system (NMES) resonator based on the defect-free graphene nanoribbon are investigated via classic molecular dynamics simulations. The graphene nanoribbons show ultrahigh fundamental resonant frequencies which can reach 189.6 GHz. The resonant frequencies increase non-monotonically with increasing externally applied force. When the external forces are between 15.912 nN and 44.2 nN, the resonant frequencies of the graphene nanoribbons remain constant at 132.9 GHz. And when the external stress is greater than 44.2 nN, the resonant frequencies show an incremental variation tendency. Temperature has a little influence on resonant frequencies. When the temperature is greater than 75 K, the resonant frequencies of the graphene nanoribbons remain constant at 132.9 GHz. The resonant characteristics of graphene nanoribbons are insensitive to the chirality. The resonant frequencies of the graphene nanoribbon exhibit significant decrease as the length-width ratio increases. © Copyright 2016 American Scientific Publishers All rights reserved.


Shi P.,Xidian University | Jin K.,Xidian University | Zheng X.,Xidian University
International Journal of Mechanical Sciences | Year: 2017

Steel and other metal alloys are widely used in various industries of the national economy. The structure failure often causes great economic losses, and threatens people's life seriously, therefore the early warning of defect becomes essential to prevent malignant accidents fundamentally. Magnetic memory method is a nondestructive testing technology that can realize the early diagnosis for the ferromagnetic material. One key issue on the magnetic memory method is to establish the quantitative relationship between the shape and size of defect and the surface magnetic memory signals. However, little investigation of this issue restricts its applications in the engineering seriously. In this paper, based on a nonlinear constitutive relation for ferromagnetic materials under a constant weak magnetic field, a magnetomechanical model is established for the magnetic memory method, and its quantitative analysis is also completed by the finite element method. Comparisons of the theoretical results for different magnetomechanical models and experimental data are presented. It shows that theoretical results obtained from the proposed model are more consistent with experimental data, and the proposed magnetomechanical model is applicable for various ferromagnetic materials. A detailed study has also been performed to reveal the effects of load magnitude, defect size, lift-off value on the magnetic memory signals. In addition, a theoretical analysis for the stress concentration problem is presented to demonstrate its feasibility for the early diagnosis. © 2017


Fei N.,Xidian University | Yang Y.,Xidian University
Cluster Computing | Year: 2017

Learning causality from data is known as the causal discovery problem, and it is an important and relatively new field. In many applications, there often exist latent variables, if such latent variables are completely ignored, which can lead to the estimation results seriously biased. In this paper, a method of combining exploratory factor analysis and path analysis (EFA-PA) is proposed to infer the causality in the presence of latent variables. Our method expands latent variables as well as their linear causal relationships with observed variables, which enhances the accuracy of causal models. Such model can be thought of as the simplest possible causal models for continuous data. The EFA-PA is very similar to that of structural equation model, but the theoretical model established by the structural equation model needs to be modified in the process of data fitting until the ideal model is established.The model gained by EFA-PA not only avoids subjectivity but also reduces estimation complexity. It is found that the EFA-PA estimation model is superior to the other models. EFA-PA can provides a basis for the correct estimation of the causal relationship between the observed variables in the presence of latent variables. The experiment shows that EFA-PA is better than the structural equation model. © 2017 Springer Science+Business Media New York


Wang Z.,Xidian University | Zhang Q.,University of Essex | Li H.,Xi'an Jiaotong University | Ishibuchi H.,Osaka Prefecture University | Jiao L.,Xidian University
Swarm and Evolutionary Computation | Year: 2017

Decomposition based multiobjective evolutionary algorithms approximate the Pareto front of a multiobjective optimization problem by optimizing a set of subproblems in a collaborative manner. Often, each subproblem is associated with a direction vector and a reference point. The settings of these parameters have a very critical impact on convergence and diversity of the algorithm. Some work has been done to study how to set and adjust direction vectors to enhance algorithm performance for particular problems. In contrast, little effort has been made to study how to use reference points for controlling diversity in decomposition based algorithms. In this paper, we first study the impact of the reference point setting on selection in decomposition based algorithms. To balance the diversity and convergence, a new variant of the multiobjective evolutionary algorithm based on decomposition with both the ideal point and the nadir point is then proposed. This new variant also employs an improved global replacement strategy for performance enhancement. Comparison of our proposed algorithm with some other state-of-the-art algorithms is conducted on a set of multiobjective test problems. Experimental results show that our proposed algorithm is promising. © 2017 Elsevier B.V.


Chen W.,University of Birmingham | Liu J.,Xidian University | He S.,University of Birmingham
BMC Systems Biology | Year: 2017

Background: Active module, defined as an area in biological network that shows striking changes in molecular activity or phenotypic signatures, is important to reveal dynamic and process-specific information that is correlated with cellular or disease states. Methods: A prior information guided active module identification approach is proposed to detect modules that are both active and enriched by prior knowledge. We formulate the active module identification problem as a multi-objective optimisation problem, which consists two conflicting objective functions of maximising the coverage of known biological pathways and the activity of the active module simultaneously. Network is constructed from protein-protein interaction database. A beta-uniform-mixture model is used to estimate the distribution of p-values and generate scores for activity measurement from microarray data. A multi-objective evolutionary algorithm is used to search for Pareto optimal solutions. We also incorporate a novel constraints based on algebraic connectivity to ensure the connectedness of the identified active modules. Results: Application of proposed algorithm on a small yeast molecular network shows that it can identify modules with high activities and with more cross-talk nodes between related functional groups. The Pareto solutions generated by the algorithm provides solutions with different trade-off between prior knowledge and novel information from data. The approach is then applied on microarray data from diclofenac-treated yeast cells to build network and identify modules to elucidate the molecular mechanisms of diclofenac toxicity and resistance. Gene ontology analysis is applied to the identified modules for biological interpretation. Conclusions: Integrating knowledge of functional groups into the identification of active module is an effective method and provides a flexible control of balance between pure data-driven method and prior information guidance. © 2017 The Author(s).


Li X.,Xidian University | Yi H.,Northwest University, China
Iranian Journal of Fuzzy Systems | Year: 2017

Matroids are important combinatorial structures and connect closely with graphs. Matroids and graphs were all generalized to fuzzy setting respectively. This paper tries to study connections between fuzzy matroids and fuzzy graphs. For a given fuzzy graph, we first induce a sequence of matroids from a sequence of crisp graph, i.e., cuts of the fuzzy graph. A fuzzy matroid, named graph fuzzy matroid, is then constructed by using the sequence of matroids. An equivalent description of graphic fuzzy matroids is given and their properties of fuzzy bases and fuzzy circuits are studied. © 2017, University of Sistan and Baluchestan. All rights reserved.


Dong Y.,Polytechnic University of Mozambique | Li S.,Xidian University | Zhang S.,Northwest University, China
Nonlinear Analysis: Real World Applications | Year: 2017

In this paper, we consider a chemical reaction–diffusion model with Degn–Harrison reaction scheme under homogeneous Neumann boundary conditions. The existence of Hopf bifurcation to ordinary differential equation (ODE) and partial differential equation (PDE) models are derived, respectively. Furthermore, by using the center manifold theory and the normal form method, we establish the bifurcation direction and stability of periodic solutions. Finally, some numerical simulations are shown to support the analytical results, and to reveal new phenomenon on the Hopf bifurcation. © 2016 Elsevier Ltd


Yang X.,Xidian University | Shao X.,Binzhou University | Gao L.,Xidian University | Zhang S.,Chinese Academy of Sciences
Briefings in Functional Genomics | Year: 2016

DNA methylation has been proved to play important roles in cell development and complex diseases through comparative studies of DNA methylation profiles across different tissues and samples. Current studies indicate that the regulation of DNA methylation to gene expression depends on the genomic locations of CpGs. Common DNA methylation patterns shared across different cell types and tissues are abundant, and they are likely involved in the basic functions of cell development, such as housekeeping functions. By way of contrast, cell type-specific DNA methylation patterns show distinct functional relevance with cell type specificity. Additionally, abnormal DNA methylation patterns are extensively involved in tumour development. Pan-cancer methylation patterns reveal common mechanisms and new similarities of different cancers, while cancer-specific patterns are relating to tumour heterogeneity and patient survival. Moreover, DNA methylation patterns in specific cancer are relevant with diverse regulatory elements such as enhancers and long non-coding RNAs. In this review, we survey the recent advances on DNA methylation patterns in normal or tumour states to illustrate their potential roles in cell development and cell canceration. © The Author 2016. Published by Oxford University Press.


Liu M.,Xidian University | Li B.,Xidian University
International Conference on Digital Signal Processing, DSP | Year: 2017

Traditional orthogonal frequency division multiplexing (OFDM) bandwidth estimation scheme can not acquire accurate estimation results in low signal to noise ratio (SNR) over multi-path channels. Besides, it acquires a great mount of computation. To deal with these problems, a novel bandwidth estimation scheme for OFDM is proposed. Firstly, the power spectrum of OFDM is estimated by the Welch method. And then, the spectrum is decomposed into many intrinsic mode functions (IMFs) by empirical mode decomposition (EMD) and the suitable IMFs are chosen according to the thresholds to reconstruct the spectrum. After that, the positions of the maximum and the minimum of the impulse are extracted in the reconstructed spectrum, which are used as the beginning and the end of the spectrum. Finally, the statistical average of the computed bandwidth is used as the final bandwidth. Simulation results show that the proposed scheme has higher precision and lower computation in low SNR over multi-path channels. © 2016 IEEE.


Guan S.,Xidian University | Li Z.,Xidian University
Neural Processing Letters | Year: 2017

This paper proposed a normalised spline adaptive filtering algorithm to improve the stability of spline adaptive filtering (SAF) algorithm against the eigenvalue spread of the autocorrelation matrix of the input signal. The new adaptive filtering algorithm is based on the normalised least mean square (NLMS) approach and the value range of the learning rate in this algorithm is specified. This algorithm is called SAF-NLMS. In this work, first the derivation of the SAF-NLMS algorithm is given. Second, detailed convergence and the computational complexity analyses are carried out. Finally, the performance of the proposed algorithm is tested according to artificial datasets and real datasets. The achieved results present actually good performance. So, in practical engineering, the algorithm can be used to solve the problem of modeling or identification of nonlinear systems. © 2017 Springer Science+Business Media New York


Sun J.,Xidian University | Li X.,Xidian University
International Conference on Signal Processing Proceedings, ICSP | Year: 2017

The problem of carrier frequency and phase synchronization exists in most wireless digital communication systems. These offsets are generally results from the Doppler effect, oscillator instabilities, and unknown transmission delays between receiver and transmitter. In this paper, we propose a joint synchronization algorithm applicable for short-burst PSK modulation systems. In the coarse estimation, the M&M estimator is utilized to guarantee wide estimation range nearly 45% of symbol rate. In order to improve the poor estimation accuracy of M&M estimator, we choose cross correlation with far spacing between two adjacent pilot blocks. The length of the pilot blocks and the spacing between pilot blocks are designed according to the requirement of bit error ratio(BER) performance loss and efficient spectrum utilization. Simulation results reveal that the proposed joint algorithm can correct very wide frequency offsets with performance near the ideal situation at limited pilot symbols. © 2016 IEEE.


Su Y.,Xidian University
International Journal of Robust and Nonlinear Control | Year: 2017

This note points out that Theorems 1 and 2 in Zhu, Xia, Fu (Int. J. Robust Nonlinear Control 2011 21(6):686–702) are incorrect. Copyright © 2014 John Wiley & Sons, Ltd. Copyright © 2014 John Wiley & Sons, Ltd.


Wang X.,Lanzhou University | Zheng X.,Xidian University | Wang P.,Lanzhou University
International Journal of Multiphase Flow | Year: 2017

The distribution and motion of inertial particles in plane turbulent wall jet are investigated using direct numerical simulation, under the assumption of one-way coupling. To our knowledge, this appears to be the first direct numerical simulation of a particle-laden plane turbulent wall jet. It is shown that, in outer part of the wall jet, the behaviour of particles closely resembles that of a free plane jet. Due to the streamwise decay of particle Stokes number, the particle streaks formed in the near wall region of the wall jet are characterized by their intensity variation, which differs significantly from those in the channel flow. The streamwise growth of the particle velocity half-width is approximately equal to that of the fluid velocity half-width and the maximum velocity of particles decays slower than that of fluid due to inertia. The outer scaling can collapse the mean particle velocity in both the inner and outer region for heavier particles. In the buffer region, the particle–fluid velocity difference can be negative or positive depending on the Stokes number since there are two competing effects, namely the memory effect and turbophoresis. In the viscous region, the larger particles are on average faster than fluid and the velocity difference is found to be self-similar depending on outer Stokes number. The near-wall distribution of velocity difference is significantly correlated with the presence of high-momentum particles which are entrained by vortical structures generated in the outer region of the wall jet. These results are useful for environmental and engineering applications. © 2017 Elsevier Ltd


Wang X.,Xidian University
Journal of Lightwave Technology | Year: 2010

A method is presented for the calculation of vector near fields of a tapered fiber probe in presence of a rotationally asymmetric sample by numerically solving boundary integral equations of two scalar Borgnis potentials. For the convenience of the description of all the boundaries, cylindrical coordinates and Cartesian coordinates are, respectively, used in the domains, where the rotationally symmetric tapered fiber probe and the rotationally asymmetric sample are located. The Borgnis potentials on the surface of the fiber probe are harmonically expanded in the azimuthal direction of the cylindrical coordinates so that the fiber probe can be treated as a 2-D structure. Only the Borgnis potentials on the surface of the sample, rather than those on all surfaces, are first calculated. The Borgnis potentials on other surfaces could be finally calculated by their relationship with the solved Borgnis potentials on the surface of the sample. With this method, the memory requirement can be considerably reduced in calculation and the method can easily extend to the solution of electromagnetic fields in structures much more complex. © 2010 IEEE


Yao Y.,Xidian University | Zhang F.,Xidian University
Electronics Letters | Year: 2017

A wideband planar endfire circularly polarised loop antenna is proposed. The antenna is fed by a microstrip line with a novel ground plane instead of a coaxial probe. The microstrip line part and the loop part generate the vertical polarisation and the horizontal polarisation, respectively. Two stubs added on the loop contribute to the bandwidth improvement. The proposed antenna achieves wide impedance bandwidth (|S11| < -10 dB) and wide 3-dB axial ratio bandwidth, both of which can cover the frequency range from 8.0 to 12.5 GHz (43.9%). © The Institution of Engineering and Technology 2017.


Zhuo L.,Xidian University | Lijuan X.,Xidian University
Electronics Letters | Year: 2017

A new parameter is introduced to the method of polarisation which is dual to the Bhattacharyya parameter in some sense. Through this parameter, the authors give an alternative proof on the result about the speed of the entropy polarising to 1. © The Institution of Engineering and Technology 2017.


Yuan X.,Xidian University | Zhang J.,Xidian University | Yang L.,Xidian University
IEEE Transactions on Biomedical Engineering | Year: 2017

Objective: Next-generation sequencing data has been widely used for DNA variant discovery and tumor study through computational tools. Effective simulation of such data with many realistic features is very necessary for testing existing tools and guiding the development of new tools. Methods: We present an integrated simulation system, IntSIM, to simulate common DNA variants and to generate sequencing reads for mixture genomes. IntSIM has three novel features in comparison with other simulation programs: 1) it is able to simulate both germline and somatic variants in the same sequence, 2) it deals with tumor purity so as to generate reads corresponding to heterogeneous genomes and also produce tumor-normal matched samples, and 3) it simulates correlations among SNPs, among CNVs/CNAs based on HMM models trained from real sequencing genomes, and can simulates broad and focal CNV/CNA events. Results: The simulation data of IntSIM can reflect characteristics observed from real data and are consistent with input parameters. The IntSIM software package is freely available at http://intsim.sourceforge.net/. Conclusion: Based on a great number of experiments, IntSIM performs better than other program for some scenarios, such as simulation of heterozygous SNPs, CNVs/CNAs, and can achieve some functions that other programs cannot achieve. Significance: Simulation with IntSIM can be expected to evaluate performance of methods in detecting various types of variants, analyzing tumor samples, and especially providing a realistic assessment of effect of tumor purity on identification of somatic mutations. © 1964-2012 IEEE.


Liu C.,Xidian University | An X.,Xidian University
Microwave and Optical Technology Letters | Year: 2017

In this article, a wideband bandpass filter is proposed, which combines substrate integrated waveguide (SIW) with four improved dumbbell defected ground structure (DGS) cells. The novel DGS, as a resonator on the metal ground, can produce two transmission zeros, aiming to improve the frequency selectivity and extend the upper stopband. The roll-off at the upper side is extremely sharper (about 58 dB/GHz). Therefore, the filter shows advantages in terms of the compact size, stopband rejection, good bandpass, and high frequency selectivity. The filter was fabricated and measured. The measured 3 dB bandwidth is from 6.85 to 11.11 GHz, representing a fractional bandwidth of 47.4% at a center frequency of 8.98 GHz. Within the passband, the insertion loss is 1.5 dB and the return loss is better than 18 dB, including the loss from two SMA connectors. The measured results and simulation results are in good agreements. © 2017 Wiley Periodicals, Inc. Microwave Opt Technol Lett 59:789–792, 2017. © 2017 Wiley Periodicals, Inc.


Hao C.,Xidian University | Hao C.,Anhui Science and Technology University | Wenping M.,Xidian University
IEEE Photonics Journal | Year: 2017

Quantum state sharing (QSTS) plays an important role in transporting, managing, and distributing keys. In this paper, by adopting the linear equation instead of using the Lagrange interpolation, a new idea of constructing (t, n) threshold quantum state sharing scheme is proposed. The best innovation is that a new tool in constructing (t, n) threshold structure is proposed. In this scheme, the dealer who possesses a sequence of one-particle unknown quantum states intends to share it with n participants and authorizes t out of them cooperate to reconstruct the sequence. First, the equations decided by the private key of dealer are constructed. Second, the dealer distributes the private keys of n participants by using the solutions to the equations just mentioned. Finally, the dealer encodes the sequence through a unitary operation, and any t out of the n participants recover the initial quantum state sequence through the unitary operations decided by the solutions to the linear equations. Compared to the existing schemes, the proposed scheme is easily realized in physical experiment, and its successful probability is 100% theoretically. © 2016 IEEE.


Liu J.,Xidian University | Guo L.-X.,Xidian University
IEEE Transactions on Antennas and Propagation | Year: 2017

A novel modeling method based on the parametric domain decomposition is proposed for the B-spline surfaces. This method combines the advantages of conventional B-spline and Bezier surfaces. Moreover, a fast algorithm based on the new modeling method is presented to locate the stationary points, including inner and boundary stationary points, of physical optics (PO) integrals from targets modeled with double-quadratic B-spline surfaces. In this algorithm, the locating problem is reduced to a numerical or analytical solution. No approximation is involved in the proposed modeling method and locating algorithm. The stationary phase method by means of the fast locating algorithm is employed to evaluate PO integrals. The CPU time is independent of the incident frequency and physical dimension of scattered surfaces. The accuracy and performance of the presented methods are validated by comparing them with those of the brute force method. © 1963-2012 IEEE.


Zhou X.,Xidian University | Zhu Z.,Xidian University
Microelectronics Journal | Year: 2017

The task mapping has a significant impact on the system performance of Network-on-Chip(NoC). In this paper, we propose a dynamic task mapping algorithm for Software-Defined-Network-on-Chip(SDNoC). The hierarchical design of SDNoC promotes the flexibility of NoC and provides the running environment for dynamic mapping algorithm with software techniques. The goal of dynamic task mapping is to minimize communication cost of the application execution and to achieve the load balance among routers. The tasks of applications are assigned to suitable network nodes by the proposed task coarse mapping and task fine mapping for minimum communication cost and flits load balance among routers. A simulation platform is presented to confirm the effectiveness of the proposed approach. The simulation results show that the communication cost and the standard deviation of routers flit load have been reduced by 2.8% and 8.1% compared with the reported dynamic mapping method. The execution time of applications and consuming time of mapping are less 9.3% and 28.2% compared with the reported dynamic mapping respectively. © 2017 Elsevier Ltd


Feng B.,Xidian University | Chen B.,Xidian University | Liu H.,Xidian University
Pattern Recognition | Year: 2017

Feature extraction is the key technique for radar automatic target recognition (RATR) based on high-resolution range profile (HRRP). Traditional feature extraction algorithms usually utilize shallow architectures, which result in the limited capability to characterize HRRP data and restrict the generalization performance for RATR. Aiming at those issues, in this paper deep networks are built up for HRRP target recognition by adopting multi-layered nonlinear networks for feature learning. To learn the stable structure and correlation of targets from unlabeled data, a deep network called Stacked Corrective Autoencoders (SCAE) is further proposed via taking the advantage of the HRRP's properties. As an extension of deep autoencoders, SCAE is stacked by a series of Corrective Autoencoders (CAE) and employs the average profile of each HRRP frame as the correction term. The covariance matrix of each HRRP frame is considered for establishing an effective loss function under the Mahalanobis distance criterion. We use the measured HRRP data to show the effectiveness of our methods. Furthermore, we demonstrate that with the proper optimization procedure, our model is also effective even with a moderately incomplete training set. © 2016 Elsevier Ltd


Xiong J.,Xidian University | Li J.,Xidian University
International Journal of Systems Science | Year: 2017

In this study, non-fragile consensus algorithm is proposed to solve the average consensus problem of a network of diffusion PDEs, modelled by boundary controlled heat equations. The problem deals with the case where the Neumann-type boundary controllers are corrupted by additive persistent disturbances. To achieve consensus between agents, a linear local interaction rule addressing this requirement is given. The proposed local interaction rules are analysed by applying a Lyapunov-based approach. The multiplicative and additive non-fragile feedback control algorithms are designed and sufficient conditions for the consensus of the multi-agent systems are presented in terms of linear matrix inequalities, respectively. Simulation results are presented to support the effectiveness of the proposed algorithms. © 2017 Informa UK Limited, trading as Taylor & Francis Group


Du N.,Xidian University | Hu H.,Xidian University
2016 European Control Conference, ECC 2016 | Year: 2016

Deadlock resolutions have been an active area of research in automated manufacturing systems (AMSs). Most researchers assume that allocated resources do not fail while few of them addresses the discrete-event supervision of AMSs that are subject to resource failures. In practice, resource failures occur unexpectedly in the context of complex system structures, e.g., AMSs with assembly operations and flexible routes. Therefore, we consider robust deadlock-free issue in systems with unreliable resources in this paper. Our objective is to develop a robust supervisory control policy that allocates resources so that parts requiring failed resources do not block the production of parts not necessarily requiring failed resources. To be specific, we hope that concerned parts can advance into the buffer space of an unreliable resource at any time in case the unreliable resource fails. Our approach is distributed, distinguished from conventional methods based on structure-oriented and monolithic specifications. One only concerns about whether currently-available resources are enough in their quantity to assist a concerned token to reach its desired destination. © 2016 EUCA.


Wen C.,Xidian University | Shi G.,Xidian University | Xie X.,Xidian University
Signal Processing | Year: 2017

We consider the problem of estimating the nominal directions of arrival (DOA) of multiple distributed sources using nested array. In practical applications, angular spread of distributed source arises due to the multipath propagation and local scattering around the vicinity of a source. DOA estimation methods based on point-source assumption are known to severely degrade in the presence of the angular spread. To solve this problem, we develop a distributed source model based approach for a nested array. Based on the concept of difference co-array, redundancy averaging technique is applied to the sample covariance matrix. By exploiting the annihilating property of the redundancy averaged terms, an efficient method based on annihilating filter (AF) is proposed. This method can be applied to the case of more sources compared with the actual physical sensors without a priori knowledge of the spreading parameters. Whereas the sample covariance matrix is corrupted by either noise or estimation error due to finite snapshots, so an AF method with structured low rank approximation (SLRA) is further proposed, which results in a better estimate. Finally, numerical simulations demonstrate the effectiveness of the proposed methods. © 2016 Elsevier B.V.


Sun B.,Xidian University | Ma W.,Tongji University
Journal of Intelligent and Fuzzy Systems | Year: 2017

This paper presents a general framework for the study of rough approximation of a fuzzy (crisp) concept in multi-universes environment, which is an extension of the original Pawlak rough set theory. The Pawlak rough set is mainly concerned with the approximation of objects confined on the same universe by an arbitrary binary relation. However, the objects (concept) may be related with three or more different universes in reality of the decision-making. This paper presents the rough set model over multi-universes, where the concept approximations are defined by using a multiple relation on the multi-universes. We firstly present the rough approximation of a fuzzy concept over multi-universes by using the multiple fuzzy relation defined on the multi-universes, i.e., the fuzzy rough set over multi-universes. Then, a number of important properties of fuzzy rough set over multi-universes are obtained. It is shown that some of the properties of the fuzzy rough set on the same universe are special instances of those of fuzzy rough set over multi-universes. Furthermore, several special rough set models over multi-universes are derived from the fuzzy rough set over multi-universes. Subsequently, we give a new approach to multiple attribute decision making (MADM) with the characteristic of uncertainty, incomplete and inaccurate available information based on fuzzy rough set over multi-universes by combing the idea of uncertainty risk decision making. The decision steps and the algorithm of the decision method are also given. The proposed approach can obtain an objectively decision result with the data information owned by the decision problem only. Finally, the validity of the decision methods is tested by a numerical example with the background of clinical medical diagnosis decision making. The main contribution of this paper is twofold. One is to present a new perspective of the universe-oriented extension for classical rough set and then establish a new generalized rough set model under the framework of multiple different universes, i.e., fuzzy rough set model over multi-universes. Another is to present an approach to multiple attribute decision making problems based on fuzzy rough set over multi-universes. © 2017 IOS Press and the authors. All rights reserved.


Zhao J.,Xidian University | Tao H.,Xidian University
Journal of Systems Engineering and Electronics | Year: 2017

The three-component electromagnetic vector sensor (EMVS) consisting of co-centered orthogonally oriented x-dipole, z-dipole and z-loop is considered. In order to make full use of the spatial aperture of each component, the original uniform linear three-component EMVS array (ULTEA) is stretched into one half-wavelength spaced uniform linear loop subarray (ULLSA) along the z axis, and one sparse uniform linear co-centered orthogonally oriented dual-dipole (CODD) subarray (SULCSA) along the x axis. Then, a generalized rotation invariance based quaternion multiple signal classification (GRIQ-MUSIC) algorithm is presented for direction of arrival (DOA) and polarization parameters estimation. According to the proposed algorithm, the elevation angles are firstly estimated based on the half-wavelength spaced ULLSA. Then the polarization phase differences and azimuth angles are obtained based on the coupling relationship between the angle domain and polarization domain, but the azimuth angles are in coarse-resolution since the array aperture is not utilized. Next, the SULCSA is used to re-estimate the azimuth angles in fine-resolution, and the ambiguity problem can be resolved by the least square method. Finally, based on the estimated elevation angles, azimuth angles and polarization phase differences, the corresponding auxiliary polarization angles can be estimated by N times one-dimensional parameter search, where N is the sources number, and the parameters are matched automatically. Based on the GRIQ-MUSIC algorithm, the high dimensional parameters search problem of the conventional Q-MUSIC algorithm is simplified to a one-dimensional parameter search problem, thus the proposed algorithm not only reduces the computation complexity considerably, but also avoids the performance degradation caused by the failure in parameters pairing. The simulation examples demonstrate the effectiveness and feasibility of the proposed algorithm. © 1990-2011 Beijing Institute of Aerospace Information.


Li T.,Xidian University | Che M.,Xidian University
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2017

The tensegrity structures suffer the axial pressure in struts and the axial tension in cables and springs, so they are widely used in many engineering fields such as architecture, biotechnology, aerospace and robotics. Based on the Lagrangian dynamics and prototype experiment, the spring deformation of the tensegrity structure under the action of external forces is analyzed and measured. First, the dynamic model of the equilibrium state of the tensegrity structure is derived. The spring deformation of the tensegrity structure under the action of external nonconservative forces is analyzed. Then, by means of the prototype experiment on the tensegrity structure with six struts and three cables, the spring deformation is measured. The comparison and analysis between the experimental and numerical results validate the dynamic model of the tensegrity structure and reveal the mathematical relation between external forces and deformation of the tensegrity structure. © 2017, The Editorial Board of Journal of Xidian University. All right reserved.


Wang W.,Xidian University | Qi J.,Xidian University
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2017

The theory of three-way concept analysis is newly developed, but so far there is no concrete algorithm for constructing three-way concepts. In order to solve this problem, a three-way concept construction algorithm named CbO3C is firstly proposed in this paper. The CbO3C adopts the idea of the construction algorithm CbO of formal concepts in formal concept analysis. At the same time, in order to improve the efficiency and lower the memory overhead, the CbO3C employs the partial closure canonicity test and inherited failure test to reduce the repeated computations of three-way concepts, applies the reduction condition to filter the non-core three-way concepts, and implements set operations on the basis of bits. The experiments with UCI and random data sets show that the CbO3C can correctly and efficiently calculate all core three-way concepts of a formal context. © 2017, The Editorial Board of Journal of Xidian University. All right reserved.


Zhang J.-J.,Xidian University | Fang M.,Xidian University | Li X.,Xidian University
Expert Systems with Applications | Year: 2017

Currently a consensus on multi-label classification is to exploit label correlations for performance improvement. Many approaches build one classifier for each label based on the one-versus-all strategy, and integrate classifiers by enforcing a regularization term on the global weights to exploit label correlations. However, this strategy might be suboptimal since it may be only part of the global weights that support the assumption. This paper proposes clustered intrinsic label correlations for multi-label classification (CILC), which extends traditional support vector machine to the multi-label setting. The predictive function of each classifier consists of two components: one component is the common information among all labels, and the other component is a label-specific one which highly depends on the corresponding label. The label-specific one representing the intrinsic label correlations is regularized by clustered structure assumption. The appealing features of the proposed method are that it separates the common information and the label-specific information of the labels and utilizes clustered structures among labels represented by the label-specific parts. The practical multi-label classification problems can be directly solved by the proposed CILC method, such as text categorization, image annotation and sentiment analysis. Experiments across five data sets validate the effectiveness of CILC, compared with six well-established multi-label classification algorithms. © 2017 Elsevier Ltd


He J.,Xidian University | Yang F.,Xidian University
IET Image Processing | Year: 2017

Rate control (RC) plays a critical role in video coding for regulating the coded bit-stream to achieve the target bitrate, which involves two basic steps: bit allocation (BA) and quantisation parameter selection. Here, the former is a key element to directly affect the performance of RC. So, in this study, an efficient frame-level BA algorithm is proposed for the latest video coding standard H.265/high-efficiency video coding (HEVC). First, by analysing the optimisation problem of the frame-level BA, two factors have been found to be related to the frame-level BA, which are inter-frame dependency and the target bitrate. Then, a measure of inter-frame dependency is put forward to reflect the correlation among consecutive frames. Finally, according to the results of allocation weights through the dynamic programming method, the relationships among the allocation weights and the two factors are investigated, and based on which the efficient BA model is established. Experimental results show that in comparison with the original RC scheme in HM-14.0, the proposed frame-level BA algorithm reduces, on average, BD-rate by 5.19% with negligible encoding time increase. In addition, the proposed algorithm also achieves higher GOP-level RC accuracy compared with the original RC scheme in HM. © The Institution of Engineering and Technology.


Ren Q.,Xidian University | Luo Q.,Shanxi Agricultural University
Key Engineering Materials | Year: 2017

Although their high-cost and complex preparation technology processing have limited their applications in engineering areas, whiskers are being increasingly used as reinforcing materials for the aim of mechanical or thermal property improvement of other materials, such as polymers. Accordingly, the work of this paper proposes the preparation of magnesium hydroxide whiskers. And the magnesium hydroxide whiskers, whose length being about 30μm and its diameter being about 3μm, was prepared by hydrothermal conditions successfully. Besides, the effect of preparation technology, which includes the reaction temperature and reaction time, was discussed according to the results of XRD, TEM, and SEM. Moreover, the mechanism of the preparation of magnesium hydroxide whiskers was studied. © 2017 Trans Tech Publications, Switzerland.


Luo Q.,Shanxi Agricultural University | Ren Q.,Xidian University
Key Engineering Materials | Year: 2017

Artificial neural net technology can reflect the relationship between the actual state development tendency and the state input signal. CaCO3 is the number one inorganic fillers in all inorganic materials used in the industry. And the continued developments of these related areas has focused research attention on the possibilities offered by CaCO3 nanocrystalline for its excellent characters. Accordingly, a three-layer structure back-propagation network model based on the non-linear relationship between the size of the CaCO3 nanocrystalline and the technological factors, such as reaction time, reaction temperature, raw material adding amount of Na2CO3 and CaCl2, was established in this paper. Moreover, in order to accelerate the converging rate and avoid the non-converging situation, the momentum terms are introduced. Besides, the variable learning speed is adopted. At the same time, the input variables were pretreated by using the main component analysis firstly. And the results show that the improved back propagation neural networks model is very efficient for predication of the CaCO3 nanocrystalline size. © 2017 Trans Tech Publications, Switzerland.


Huang D.,Xidian University | Xu W.,Northwestern Polytechnical University
Nonlinear Dynamics | Year: 2017

The paper mainly presents the dynamical characteristics of a base-excited viscoelastic isolation system with real-power geometric nonlinearities under a delayed PPF controller. This controller is coupled to the main system with 1:1 internal resonance. Firstly, the perturbation method of multiple scales is adopted to explicitly find the coupled relationship of the frequency response equations. The results demonstrate that under over-linear restoring force, the amplitude–frequency responses of the viscoelastic isolation system are of the hardening type, which only appears on the right branch of the double-peak response. In this respect, increasing the detuning parameter of the controller results in the appearance of frequency island phenomenon on the right branch of the double-peak response, while the amplitude of the controller degenerates into the traditional single-peak response along with the frequency island. Then, it is worth noting that the vibration can be suppressed effectively by the viscoelastic damping parameters. Furthermore, eight types of interesting dynamical response phenomena are found with the change in time delays under different excitation amplitudes. To this end, the stability analysis, showing the performance of the controller strategy, is carried out by combining the response characteristics. Finally, from the perspective of suppressing the peak amplitude and maintaining the resonance stability, the suitable feedback gains and time delays are determined by means of frequency responses as well as stability conditions. © 2017 Springer Science+Business Media Dordrecht


Fan K.,Xidian University | Wei B.,Xidian University
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

The near-field broadband electric field coupling antenna has many remarkable advantages, such as simple operation, safe connection and high efficient transmission of large capacity data. In recent years, it has been widely used in many fields. The TranferJet™ antenna mentioned in this paper is a typical representative of the high-speed near-field wireless technology. The target of broadening bandwidth and dual-band has been come true by transforming the form of the micro-strip line and coupled electrode. It shows the performance of the improved antenna employing 3D electromagnetic simulation software to simulate. © 2016 IEEE.


Guo L.-J.,Xidian University | Guo L.-X.,Xidian University
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

The propagation properties of THz electromagnetic wave (EM wave) in a magnetized plasma which is inhomogeneous in both collision frequency and electron density are analyzed theoretically in this study. By utilizing the scattering matrix method (SMM) method, the effects of Electron density, collision frequency, the thickness of the plasma and the electron temperature on the absorption coefficient are analyzed numerically. It is found that these plasma parameters can cause significant change in the absorption spectra. Specifically speaking, the characteristics of the absorption coefficient, absorption peak, and absorption valley are all influenced by these typical parameters. © 2016 IEEE.


Lei J.,Xidian University | Hao Y.,Queen Mary, University of London
2016 Loughborough Antennas and Propagation Conference, LAPC 2016 | Year: 2016

Quasi-conformal transformation optics (QCTO) provides a practical approach to design nonmagnetic broadband medium for electromagnetic devices, here we present a novel hybrid method of QCTO with low sidelobe array synthesis, and apply it to the conformal phased array antenna (PAA) design. Effective approximation of relative permittivity is used to avoid metamaterials with dielectric constant lower than unity during the coordinate transformation. Taking the conformal cylindrical array as example, numerical simulations are given to show how arbitrary non-uniform PAA based on all dielectric QCTO lens can scan as a uniformly spaced linear PAA with low sidelobe level (SLL), which makes the advantages of linear array such as simple array synthesis and beamforming, can be achievable by an arbitrary array with complex geometry. © 2016 IEEE.


He H.,Xidian University | Guo L.,Xidian University
ISAPE 2016 - Proceedings of the 11th International Symposium on Antennas, Propagation and EM Theory | Year: 2016

A multi-hybrid method combining numerical vector finite-element method/boundary integral method (FEM/BIM) and analytic Kirchhoff approximation (KA) is employed in this paper to study the scattering from a 3-D object above a 2-D conductive rough surface. The scattering from the target is studied by hybrid vector FEM/BIM while KA is applied on the underlying rough surface to reduce the computation time and memory requirement. An iterative approach is employed to take into account the multiple interaction between the target and underlying rough surface. Using the Monte Carlo method to generate 2-D Gaussian rough surface, bistatic difference field radar cross section (d-RCS) of A 3-D dielectric target above a 2D conductive rough surface is numerically simulated. © 2016 IEEE.


Wu T.,Xidian University | Wu T.,Hong Kong Polytechnic University | Wang L.,Peking University | Fu F.,Dartmouth College
PLoS Computational Biology | Year: 2017

Phenotypic diversity is considered beneficial to the evolution of contingent cooperation, in which cooperators channel their help preferentially towards others of similar phenotypes. However, it remains largely unclear how phenotypic variation arises in the first place and thus leads to the construction of phenotypic complexity. Here we propose a mathematical model to study the coevolutionary dynamics of phenotypic diversity and contingent cooperation. Unlike previous models, our model does not assume any prescribed level of phenotypic diversity, but rather lets it be an evolvable trait. Each individual expresses one phenotype at a time and only the phenotypes expressed are visible to others. Moreover, individuals can differ in their potential of phenotypic variation, which is characterized by the number of distinct phenotypes they can randomly switch to. Each individual incurs a cost proportional to the number of potentially expressible phenotypes so as to retain phenotypic variation and expression. Our results show that phenotypic diversity coevolves with contingent cooperation under a wide range of conditions and that there exists an optimal level of phenotypic diversity best promoting contingent cooperation. It pays for contingent cooperators to elevate their potential of phenotypic variation, thereby increasing their opportunities of establishing cooperation via novel phenotypes, as these new phenotypes serve as secret tags that are difficult for defector to discover and chase after. We also find that evolved high levels of phenotypic diversity can occasionally collapse due to the invasion of defector mutants, suggesting that cooperation and phenotypic diversity can mutually reinforce each other. Thus, our results provide new insights into better understanding the coevolution of cooperation and phenotypic diversity. © 2017 Wu et al.


Ping X.,Xidian University | Ping X.,and The Key Laboratory of Electronic Equipment Structure Design
Asian Journal of Control | Year: 2017

For the linear parameter varying (LPV) system with available scheduling parameter and bounded disturbance, a synthesis approach to output feedback robust model predictive control (OFRMPC) is considered. By applying the technique of quadratic boundedness, the on-line method with the refreshment of the bounds of estimation error guarantees the robust stability of the augmented closed-loop system. For reducing the on-line computational burden, the look-up table that stores off-line optimized control laws and the corresponding regions of attraction is constructed. The on-line control law is searched based on the bounds of estimation error set and the region of attraction with the closest containment of the real-time estimated state. A continuous stirred tank reactor (CSTR) model is given to illustrate the effectiveness of the method. © 2017 Chinese Automatic Control Society and John Wiley & Sons Australia, Ltd.


Zhang W.,Xidian University | Zhang W.,Chinese Academy of Sciences | Pasalic E.,University of Primorska
Information Sciences | Year: 2017

In this article we improve the lower bound on the maximum nonlinearity of 1-resilient Boolean functions, for n even, by proposing a method of constructing this class of functions attaining the best nonlinearity currently known. Thus for the first time, at least for small values of n, the upper bound on nonlinearity can be reached in a deterministic manner in difference to some heuristic search methods proposed previously. The nonlinearity of these functions is extremely close to the maximum nonlinearity attained by bent functions and it might be the case that this is the highest possible nonlinearity of 1-resilient functions. Apart from this theoretical contribution, it turns out that the cryptographic properties of these functions are overall good apart from their moderate resistance to fast algebraic attacks (FAA). This weakness is repaired by a suitable modification of the original functions giving a class of balanced functions with almost optimal resistance to FAA whose nonlinearity is better than the nonlinearity of other methods. © 2016 Elsevier Inc.


Liu L.,Xidian University | Ye J.,University of Sichuan
International Journal of Network Security | Year: 2017

Re-encryption (or proxy re-encryption) is a very useful cryptographic primitive which is able to transform a ciphertext under one public key into a new ciphertext encrypting the same message but under another different public key. It plays an important role in modern secure communication and information exchange via various kinds of network infrastructure. In addition to traditional public-key encryption scheme, re-encryption can also come into force in other cryptosystems like Identity-Based Encryption (IBE) and more advanced Functional Encryption (FE), making the enhanced schemes more powerful as well as easy-to-use. In this work, we have proposed a novel identity-based proxy re-encryption (IBPRE) scheme which to the maximum extent reduces the workloads in the user side by delivering the re-encryption key (RK) generation work to the proxy server. Besides, it is likewise able to prevent possible bottlenecks for the users, like re-encryption key management.


Yan X.,Xidian University | Qin H.,Xidian University | Li J.,Xidian University
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2017

We present a new multi-focus image fusion method based on dictionary learning with a rolling guidance filter to fusion of multi-focus images with registration and mis-registration. First, we learn a dictionary via several classical multi-focus images blurred by a rolling guidance filter. Subsequently, we present a new model for focus regions identification via applying the learned dictionary to input images to obtain the corresponding focus feature maps. Then, we determine the initial decision map via comparing the difference of the focus feature maps. The latter is to optimize the initial decision map and perform it on input images to obtain fused images. Experimental results demonstrate that the suggested algorithm is competitive with the current state of the art and superior to some representative methods when input images are well registered and mis-registered. © 2017 Optical Society of America.


Li W.,Xidian University | Li H.,Xidian University
Proceedings - 2016 IEEE 1st International Conference on Data Science in Cyberspace, DSC 2016 | Year: 2016

The popularity of big data has resulted in the proliferation of applications and services with a lot of conveniences in social networks. Unfortunately, the diverse data sets contain users' privacy-sensitive information, which brings about privacy concerns potentially if the information is released or shared to the service provider. The existing practical techniques for big data privacy protection aims at anonymizing data via generalisation to satisfy a given privacy model. However, most widely-adopted privacy-preserving schemes ignore the privacy of the original data, which are generated from the initial organization or individual. In this paper, we formulated a general architecture of big data privacy to illustrate the basic structure of big data privacy. Specifically, we designed a Local Record-Driving Mechanism (LRDM) to achieve privacy-protecting for big data, which contains a methodology for organization or individual to find a privacy-preserving scheme. At the same time, we proposed a privacy metric to measure their privacy degree in big data scenario. Finally, thorough analysis and evaluation results show the effectiveness and efficiency of our proposed strategies and solution. © 2016 IEEE.


News Article | April 28, 2017
Site: www.cemag.us

A “chemical imaging” system that uses a special type of laser beam to penetrate deep into tissue might lead to technologies that eliminate the need to draw blood for analyses including drug testing and early detection of diseases such as cancer and diabetes. The system, called stimulated Raman projection microscopy and tomography, makes possible “volumetric imaging” without using fluorescent dyes that might affect biological functions and hinder accuracy, said Ji-Xin Cheng, a professor in Purdue University’s Weldon School of Biomedical Engineering, Department of Chemistry and Birck Nanotechnology Center. “Volumetric chemical imaging allows a better understanding of the chemical composition of three-dimensional complex biological systems such as cells,” he said. The technology uses a type of laser beam called a Bessel beam, which maintains focus for a longer distance than a traditional “Gaussian beam” used in other imaging technologies, making it possible to penetrate deep into tissue. Stimulated Raman spectroscopy eliminates the need for fluorescent dyes. The technology yields more accurate data than other methods because it allows imaging of the entire cell by “adding up” signals produced from the scanning beam, Cheng said. Because the Bessel beam makes possible deep-tissue imaging, it could lead to systems that eliminate the need to draw blood for analyses such as drug testing and detection of biomarkers for non-invasive early diagnosis of diseases, Cheng said. “This is a long-term goal,” he said. “In the meantime, much more research is needed to improve the system.” The researchers proved the concept by imaging fat storage in living cells. Findings are detailed in a research paper appearing on April 24 in the journal Nature Communications. The reported technology yields information about chemical composition, collecting a series of images while rotating the sample and reconstructing the 3-D structure through image reconstruction algorithms. The Bessel beam is produced using a pair of cone-shaped “axicon” lenses and is combined with a microscope objective. Its use for volumetric fluorescence imaging was previously demonstrated by physicist Eric Betzig, who won the Nobel Prize in chemistry in 2014 for his pioneering contribution to super-resolution fluorescence microscopy. Super-resolution technology allows researchers to resolve structural features far smaller than the wavelength of visible light, sidestepping the “diffraction limit” that normally prevents imaging of features smaller than about 250 nanometers, which is large compared to certain biological molecules and structures in cells. However, fluorescence microscopy usually requires the use of fluorescent tags, which may interfere with biological processes and hinder accuracy for determining chemical structure. Future research will include work to increase the detection sensitivity of the system and improve the imaging quality and speed. “There is plenty of room for improvement,” Cheng said. “The system is based on a bulky and relatively expensive femtosecond laser, which limits its potential for broad use and clinical translation. Nevertheless, we anticipate that this limitation can be circumvented through engineering innovations to reduce the cost and size of our technology. We also note that the Bessel beam can be produced using fibers, which could simplify the system and enable endoscopic applications.” The paper was authored by Xueli Chen, a visiting scholar from Xidian University in China; Purdue postdoctoral research associate Chi Zhang; Purdue doctoral students Peng Lin and Kai-Chih Huang; Xidian University researchers Jimin Liang and Jie Tian; and Cheng. The research was supported by funds from the Keck Foundation and National Institutes of Health.


News Article | April 27, 2017
Site: phys.org

The system, called stimulated Raman projection microscopy and tomography, makes possible "volumetric imaging" without using fluorescent dyes that might affect biological functions and hinder accuracy, said Ji-Xin Cheng, a professor in Purdue University's Weldon School of Biomedical Engineering, Department of Chemistry and Birck Nanotechnology Center. "Volumetric chemical imaging allows a better understanding of the chemical composition of three-dimensional complex biological systems such as cells," he said. The technology uses a type of laser beam called a Bessel beam, which maintains focus for a longer distance than a traditional "Gaussian beam" used in other imaging technologies, making it possible to penetrate deep into tissue. Stimulated Raman spectroscopy eliminates the need for fluorescent dyes. The technology yields more accurate data than other methods because it allows imaging of the entire cell by "adding up" signals produced from the scanning beam, Cheng said. Because the Bessel beam makes possible deep-tissue imaging, it could lead to systems that eliminate the need to draw blood for analyses such as drug testing and detection of biomarkers for non-invasive early diagnosis of diseases, Cheng said. "This is a long-term goal," he said. "In the meantime, much more research is needed to improve the system." The researchers proved the concept by imaging fat storage in living cells. Findings are detailed in a research paper appearing on April 24 in the journal Nature Communications. The reported technology yields information about chemical composition, collecting a series of images while rotating the sample and reconstructing the 3-D structure through image reconstruction algorithms. The Bessel beam is produced using a pair of cone-shaped "axicon" lenses and is combined with a microscope objective. Its use for volumetric fluorescence imaging was previously demonstrated by physicist Eric Betzig, who won the Nobel Prize in chemistry in 2014 for his pioneering contribution to super-resolution fluorescence microscopy. Super-resolution technology allows researchers to resolve structural features far smaller than the wavelength of visible light, sidestepping the "diffraction limit" that normally prevents imaging of features smaller than about 250 nanometers, which is large compared to certain biological molecules and structures in cells. However, fluorescence microscopy usually requires the use of fluorescent tags, which may interfere with biological processes and hinder accuracy for determining chemical structure. Future research will include work to increase the detection sensitivity of the system and improve the imaging quality and speed. "There is plenty of room for improvement," Cheng said. "The system is based on a bulky and relatively expensive femtosecond laser, which limits its potential for broad use and clinical translation. Nevertheless, we anticipate that this limitation can be circumvented through engineering innovations to reduce the cost and size of our technology. We also note that the Bessel beam can be produced using fibers, which could simplify the system and enable endoscopic applications." The paper was authored by Xueli Chen, a visiting scholar from Xidian University in China; Purdue postdoctoral research associate Chi Zhang; Purdue doctoral students Peng Lin and Kai-Chih Huang; Xidian University researchers Jimin Liang and Jie Tian; and Cheng. Explore further: Imaging uses 'photothermal effect' to peer into living cells More information: Xueli Chen et al. Volumetric chemical imaging by stimulated Raman projection microscopy and tomography, Nature Communications (2017). DOI: 10.1038/ncomms15117


Li-Xia L.,Xidian University | Yi-Qi Z.,Xidian University | Liu X.-Y.,Hunan University of Science and Technology
Expert Systems with Applications | Year: 2011

The construction of tax forecasting model is difficult due to its uncertain, non-linear, dynamic and complicated characteristics. It is difficult to describe the non-linear characteristics of tax forecasting by traditional methods. In the study, the novel forecasting method based on the combination of support vector machine (SVM) and particle swarm optimization (PSO) is proposed to the tax forecasting. The non-linear relationship in tax forecasting is efficiently represented by support vector machine, and particle swarm optimization is used to select the training parameters of support vector machine. The tax forecasting model is constructed by support vector machine optimized by particle swarm optimization (PSVM) on the basis of research for the proposed forecasting model. The tax forecasting cases are used to testify the forecasting performance of the proposed model. The experimental results demonstrate that the proposed PSVM model has good forecasting performance. © 2010 Elsevier Ltd. All rights reserved.


Shi Q.,Zhejiang Sci-Tech University | Shi Q.,Xidian University | Liu L.,National University of Singapore | Xu W.,Zhejiang Sci-Tech University | And 2 more authors.
IEEE Transactions on Wireless Communications | Year: 2014

This paper studies a multi-user multiple-input single-output (MISO) downlink system for simultaneous wireless information and power transfer (SWIPT), in which a set of single-antenna mobile stations (MSs) receive information and energy simultaneously via power splitting (PS) from the signal sent by a multi-antenna base station (BS). We aim to minimize the total transmission power at BS by jointly designing transmit beamforming vectors and receive PS ratios for all MSs under their given signal-to-interference-plus- noise ratio (SINR) constraints for information decoding and harvested power constraints for energy harvesting. First, we derive the sufficient and necessary condition for the feasibility of our formulated problem. Next, we solve this non-convex problem by applying the technique of semidefinite relaxation (SDR). We prove that SDR is indeed tight for our problem and thus achieves its global optimum. Finally, we propose two suboptimal solutions of lower complexity than the optimal solution based on the principle of separating the optimization of transmit beamforming and receive PS, where the zero-forcing (ZF) and the SINR-optimal based transmit beamforming schemes are applied, respectively. © 2002-2012 IEEE.


Chen W.,University of Science and Technology Beijing | Chen W.,Xidian University | Li X.,Baoji University of Arts And Sciences | Ren W.,University of California at Riverside | Wen C.,Nanyang Technological University
IEEE Transactions on Automatic Control | Year: 2014

This note addresses the adaptive consensus problem of first-order and second-order linearly parameterized multi-agent systems with unknown identical control directions. First, we propose a new Nussbaum-type function based on which a key lemma is established. The lemma plays an important role in analyzing the consensus of the closed-loop multi-agent systems. Second, the Nussbaum-type function is used to design adaptive control laws for first-order and second-order linearly parameterized multi-agent systems so that each agent seeks for the unknown control direction adaptively and cooperatively. Then, under the assumption that the interconnection topology is undirected and connected, it is proved that the first-order and second-order multi-agent systems can achieve consensus by choosing proper design parameters. Two simulation examples are given to illustrate the effectiveness of the proposed control laws. © 1963-2012 IEEE.


Ling B.,Xidian University | Liu Y.,Beijing Normal University
BIT Numerical Mathematics | Year: 2014

Estimates are given for the optimal recovery of functions in d variables, which are known to have (r-1)st absolutely continuous and rth bounded derivatives in any direction over, either a bounded convex d-dimensional body G, or which are periodic over a d dimensional lattice. The information is the values of the function and all its derivatives of order less than r at n points. We obtain some asymptotic estimates for this problem, and some exact results for several special cases which contain the results of Babenko, Borodachov, and Skorokhodov. © 2013 Springer Science+Business Media Dordrecht.


Yang L.,Guangdong University of Technology | Yang L.,Xidian University | Yang L.,Nanjing Southeast University | Hasna M.O.,Qatar University | Gao X.,Nanjing Southeast University
Optics Express | Year: 2014

In this paper, we consider a free-space optical (FSO) communication with multiple receive apertures over M-distributed turbulence channels with pointing errors. In particular, we consider two different combining schemes at the receiver: optimal combining (OC) and selection combining (SC). With these setups, the statistic characters of the instantaneous electrical signal-to-noise ratio (SNR) are derived. Then, using the cumulative density function (CDF)-based method, we analyze the asymptotic bit-error rate (BER) performance. The derived results help quantifying the diversity order of our considered systems. © 2014 Optical Society of America.


Gao S.,Xidian University | Wu T.,Xidian University | Wang L.,Peking University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2015

Evolution of parochial altruism is studied in a well-mixed population subdivided into two groups. Individuals' strategy is contingent on interacting partners' group property. Participants from the same group play prisoner's dilemma game, otherwise they play punishment game. We specify precisely the game parameters scope in which parochial altruism is favored for weak selection. For low mutation, we find that intergroup conflict can promote the evolution of parochial altruism. However, parochial altruism can never be favored for high mutation. We also present the conditions under which parochial altruism enjoys a higher frequency than neutral drift for intermediate mutation. © 2014 Elsevier B.V. All rights reserved.


Cheng X.,Peking University | Yao Q.,Shandong University | Yao Q.,Heriot - Watt University | Wen M.,Peking University | And 3 more authors.
IEEE Journal on Selected Areas in Communications | Year: 2013

In this paper, we propose a new regular-shaped geometry-based stochastic model (RS-GBSM) for non-isotropic scattering wideband multiple-input multiple-output vehicle-to-vehicle (V2V) Ricean fading channels. By correcting the unrealistic assumption widely used in current RS-GBSMs, the proposed model can more practically study the impact of the vehicular traffic density on channel statistics for different time delays. From the proposed model, we derive the Doppler power spectral density (PSD) and find that highly dynamic Doppler spectrum appears for V2V channels. Excellent agreement is achieved between the derived Doppler PSD and measured data, demonstrating the utility of the proposed model. To combat the intercarrier interference (ICI) caused by highly dynamic Doppler spectrum in real orthogonal frequency division multiplexing based V2V systems, this paper proposes a new type of ICI cancellation scheme, named as precoding based cancellation (PBC) scheme. The proposed scheme can be easily implemented into real V2V systems with the same ICI mitigation performance as the current best ICI cancellation scheme that has high complexity. To further improve the performance of the proposed PBC scheme, a new phase rotation aided (PRA) method, namely constant PRA (CPRA) method, is proposed. Compared with the existing PRA method, the CPRA method has better performance and much less implementation complexity. Therefore, the proposed PBC scheme with the CPRA method is the best ICI cancellation scheme for real V2V systems. © 1983-2012 IEEE.


Li C.,Xidian University | Zhuang Y.,Xidian University | Di S.,Peking University | Han R.,Northwestern Polytechnical University
IEEE Transactions on Electron Devices | Year: 2013

With the exact solution of the 2-D Poisson's equation in cylindrical coordinates, analytical subthreshold behavior models for junctionless cylindrical surrounding-gate (JLCSG) MOSFETs are developed. Using these analytical models, subthreshold characteristics of JLCSG MOSFETs are investigated in terms of channel electrostatic potential distribution, subthreshold current, and subthreshold slope (SS). It is shown that the electrostatic potential distribution, subthreshold current, and SS predicted by the analytical models are in close agreement with 3-D numerical simulation results without the need of any fitting parameters. These analytical models not only provide useful physical insight into the subthreshold behaviors, but also offer basic design guideline for the nanoscale JLCSG MOSFETs. © 1963-2012 IEEE.


Li Z.,Xidian University | Li Z.,King Saud University | Wu N.,Guangdong University of Technology | Zhou M.,Tongji University | Zhou M.,New Jersey Institute of Technology
IEEE Transactions on Systems, Man and Cybernetics Part C: Applications and Reviews | Year: 2012

Deadlocks are a rather undesirable situation in a highly automated flexible manufacturing system. Their occurrences often deteriorate the utilization of resources and may lead to catastrophic results in safety-critical systems. Graph theory, automata, and Petri nets are three important mathematical tools to handle deadlock problems in resource allocation systems. Particularly, Petri nets are considered as a popular formalism because of their inherent characteristics. They received much attention over the past decades to deal with deadlock problems, leading to a variety of deadlock-control policies. This study surveys the state-of-the-art deadlock-control strategies for automated manufacturing systems by reviewing the principles and techniques that are involved in preventing, avoiding, and detecting deadlocks. The focus is deadlock prevention due to its large and continuing stream of efforts. A control strategy is evaluated in terms of computational complexity, behavioral permissiveness, and structural complexity of its deadlock-free supervisor. This study provides readers with a conglomeration of the updated results in this area and facilitates engineers in finding a suitable approach for their industrial scenarios. Future research directions are finally discussed. © 2012 IEEE.


Wu N.,Guangdong University of Technology | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
IEEE Transactions on Semiconductor Manufacturing | Year: 2010

When scheduling cluster tools under wafer residency time constraints, wafer sojourn time in a processing module should be carefully controlled such that it is in a permissive range. Activity time variation often results in wafer sojourn time fluctuation and makes an originally feasible schedule infeasible. Thus, it is very important to know how the wafer sojourn time changes when activity time varies. With bounded activity time variation considered, this paper conducts a detailed analysis of wafer sojourn time variation in dual-arm cluster tools. To do so, a Petri net (PN) model and a real-time control policy are presented. Based on the PN model, real-time operational architecture, and real-time control policy, this paper analyzes the effect of activity time variation on wafer sojourn time delay at a process module and presents its upper bounds. The upper bounds are given in an analytical form and can be easily evaluated. With the wafer sojourn time analysis, it is possible to develop an effective method for schedulability analysis and optimal steady-state scheduling. An example is used to show the applications of the proposed approach. © 2010 IEEE.


Song X.,Peking University | Zhang Y.,Xidian University | Liu Y.,Peking University
PLoS ONE | Year: 2014

Resting state-fMRI studies have found that the inter-areal correlations in cortical networks concentrate within ultra-low frequencies (0.01-0.04 Hz) while long-distance connections within subcortical networks distribute over a wider frequency range (0.01-0.14 Hz). However, the frequency characteristics of regional homogeneity (ReHo) in different areas are still unclear. To examine the ReHo properties in different frequency bands, a data-driven method, Empirical Mode Decomposition (EMD), was adopted to decompose the time series of each voxel into several components with distinct frequency bands. ReHo values in each of the components were then calculated. Our results showed that ReHo in cortical areas were higher and more frequency-dependent than those in the subcortical regions. BOLD oscillations of 0.02-0.04 Hz mainly contributed to the cortical ReHo, whereas the ReHo in limbic areas involved a wider frequency range and were dominated by higher-frequency BOLD oscillations (>0.08 Hz). The frequency characteristics of ReHo are distinct between different parts of the striatum, with the frequency band of 0.04-0.1 Hz contributing the most to ReHo in caudate nucleus, and oscillations lower than 0.02 Hz contributing more to ReHo in putamen. The distinct frequency-specific ReHo properties of different brain areas may arise from the assorted cytoarchitecture or synaptic types in these areas. Our work may advance the understanding of the neural-physiological basis of local BOLD activities and the functional specificity of different brain regions. © 2014 Song et al.


Chen C.,Nanjing University of Posts and Telecommunications | Liang J.,Xidian University | Zhu X.,Nanjing University of Posts and Telecommunications
Pattern Recognition | Year: 2011

In this paper, we proposed an improved two-level dynamic Bayesian network layered time series model (LTSM), which aims to solve the limitations hindering the application of available dynamic Bayesian networks, the hidden Markov model (HMM) and the dynamic texture (DT) model to gait recognition. In the first level, a gait silhouette or feature cycle is divided into several temporally adjacent clusters. Each cluster is modeled by a DT or logistic DT (LDT). In the second level, HMM is built to describe the relationship among the DTs/LDTs. Besides LTSM, LDT is also an improved dynamic Bayesian network presented in this paper to describe the binary image sequence, which introduces the logistic principle component analysis (PCA) to learning its parameters. We demonstrated the validity of LTSM with experiments on both the CMU Mobo gait database and CASIA gait database (dataset B), and that of LDT on the CMU Mobo gait database. Experimental results showed the superiority of the improved dynamic Bayesian networks. © 2010 Elsevier Ltd. All rights reserved.


Zhang D.,Xidian University | Yang F.,Clemson University | Wang K.-C.,Clemson University | Huang Y.,Clemson University
Journal of Power Sources | Year: 2012

Power management system (PMS) is critical for driving electronic loads using energy harvested by microbial fuel cells (MFCs). Two promising MFC PMS designs, charge pump-capacitor-converter type and capacitor-transformer- converter type, are presented and compared in their performance in driving a wireless sensing system. It is found that the capacitor-transformer-converter type PMS can accommodate lower input voltages, but the charge pump-capacitor-converter type PMS has a slightly higher power efficiency. Furthermore, the charging speed of the capacitor-transformer-converter type PMS is not limited by the charge pump as in the charge pump-capacitor-converter type PMS, resulting in a shorter charging/discharging cycle. The findings suggest that for loads with large duty cycles comparable to the charging time, the charge pump-capacitor-converter type PMS is recommended for its higher power efficiency; on the other hand, for ultra-low MFC output and/or time-sensitive missions, the capacitor-transformer-converter type PMS is recommended for its wider input voltage range and shorter charging/discharging cycle. Highlights: Different power management systems (PMSs) for microbial fuel cells are evaluated. Charge pump-capacitor-converter type PMS has a higher power efficiency. Capacitor-transformer-converter type PMS has a shorter charging/discharging cycle. © 2012 Elsevier B.V. All rights reserved.


Yang F.,Clemson University | Zhang D.,Xidian University | Wang K.-C.,Clemson University | Huang Y.,Clemson University
Journal of Power Sources | Year: 2012

Microbial fuel cells (MFCs) are emerging as a promising alternative renewable energy source, especially for remote monitoring applications. Due to its low voltage and power output, MFCs are unable to directly drive most commercial electronic devices. A power management system (PMS) is needed to accumulate MFC energy first and then drive the load intermittently. In this study, a transformer-based PMS is proposed, which is able to function under a lower voltage input than other available MFC PMS designs. Two super-capacitors are included in the proposed PMS. The first is analytically optimized to maximize the average harvested power, while the second is selected based on the energy required to drive a given load. A continuous-mode MFC was built and used to successfully drive an IEEE 802.15.4 wireless sensor system using the proposed PMS. Experimental results showed that the proposed PMS worked well under a very low input voltage (0.18 V). The configuration of two super-capacitors and a transformer in this transformer-based PMS provides more flexibility in harvesting power from MFCs. © 2012 Elsevier B.V. All rights reserved.


Su Y.,Xidian University
Journal of Guidance, Control, and Dynamics | Year: 2015

An improved design for global finite-time stabilization of spacecraft is presented. Specifically, two very simple finite-time proportional-derivative (FPD) controllers are proposed. The proposed controls ensure global finite-time stabilization. Advantages of the proposed controllers include an absence of modeling parameters in the control law formulation and an ability to ensure finite-time stability at the origin globally within a finite time. Additionally, they are more intuitive and easy to implement. Simulations demonstrate the effectiveness and improved performances of the proposed nonlinear proportional-derivative controls. featuring fast transient and high-precision performances.


Chen W.,Xidian University | Ren W.,University of California at Riverside
Automatica | Year: 2016

This paper focuses on the event-triggered zero-gradient-sum algorithms for a distributed convex optimization problem over directed networks. The communication process is driven by trigger conditions monitored by nodes. The proposed trigger conditions are decentralized and just depend on each node's own state. In the continuous-time case, we propose an algorithm based on a sample-based monitoring scheme. In the discrete-time case, we propose a new event-triggered zero-gradient-sum algorithm which is suitable for more general network models. It is proved that two proposed event-triggered algorithms are exponentially convergent if the design parameters are chosen properly and the network topology is strongly connected and weight-balanced. Finally, we illustrate the advantages of the proposed algorithms by numerical simulation. © 2015 Elsevier Ltd. All rights reserved.


Zhang Q.,Xidian University | Ma Z.,Xidian University | Wang L.,Peking University
Pattern Recognition Letters | Year: 2013

In most of complex wavelet based fusion methods, only magnitude (or absolute value) of a complex coefficient is considered and phase information is neglected. However, more salient image features can be determined by the phase. In this paper, a multimodality image fusion algorithm is proposed with the shiftable complex directional pyramid transform (SCDPT), where phase and magnitudes of complex coefficients are jointly considered. Firstly, a novel similarity index (CCC-EM) is presented by combining the circular correlation coefficient (CCC) of relative phase angles and the traditional energy matching (EM) index. When bandpass directional subband coefficients are merged, the CCC-EM index is employed as the similarity measure and three types of regions between source images are determined for each bandpass directional subband. Then, based on some weights or salience measures, different fusion rules are designed for each type of regions. Especially, for regions with similarity in energy and positive or negative correlation relationship in relative phase, the weighted circular variance (WCV) of relative phase angles is employed. When lowpass subband coefficients are merged, the traditional structural similarity index is employed to distinguish different types of regions. For most of regions, the local energy of lowpass subband coefficients is employed as weights or salience measures. While for regions with similar intensity values but different intensity variation directions, an inter-scale based salience measure is defined by combining the local energy of the lowpass subband coefficients and the WCV of the coarsest bandpass directional subband coefficients. Several pairs of multimodality images are fused with the proposed methods. Fusion results demonstrate that the proposed fusion method can extract more salient features (not just in energy) from source images than some other complex wavelet based fusion methods. Especially, more phase information of source images can be preserved into the fused image, which makes the proposed fusion method with higher performance in spatial consistency. © 2012 Elsevier B.V. All rights reserved.


Wu T.,Xidian University | Fu F.,ETH Zurich | Dou P.,Xidian University | Wang L.,Peking University
Physica A: Statistical Mechanics and its Applications | Year: 2014

Previous studies mainly consider the random selection pattern in which individuals randomly choose reference models from their neighbors for strategy updating. However, the random selection pattern is unable to capture all real world circumstances. We institute a spatial model to investigate the effects of influence-based reference selection pattern on the evolution of cooperation in the context of public goods games. Whenever experiencing strategy updating, all the individuals each choose one of its neighbors as a reference with the probability proportional to this neighbor's influence. Levels of individuals' influence are dynamical. When an individual is imitated, the level of its influence increases, thus constituting a positive feedback between the frequencies of individuals being imitated and the likelihood for them to be reference models. We find that the level of collective cooperation can be enhanced whenever the influence-based reference selection pattern is integrated into the strategy updating process. Results also show that the evolution of cooperation can be promoted when the increase in individuals' frequency of being imitated upholds their influence in large magnitude. Our work may improve the understanding of how influence-based selection patterns promote cooperative behavior. © 2014 Elsevier B.V. All rights reserved..


Li J.,Xidian University | Huang X.,Fujian Normal University | Li J.,Nankai University | Chen X.,Xidian University | Xiang Y.,Deakin University
IEEE Transactions on Parallel and Distributed Systems | Year: 2014

Attribute-Based Encryption (ABE) is a promising cryptographic primitive which significantly enhances the versatility of access control mechanisms. Due to the high expressiveness of ABE policies, the computational complexities of ABE key-issuing and decryption are getting prohibitively high. Despite that the existing Outsourced ABE solutions are able to offload some intensive computing tasks to a third party, the verifiability of results returned from the third party has yet to be addressed. Aiming at tackling the challenge above, we propose a new Secure Outsourced ABE system, which supports both secure outsourced key-issuing and decryption. Our new method offloads all access policy and attribute related operations in the key-issuing process or decryption to a Key Generation Service Provider (KGSP) and a Decryption Service Provider (DSP), respectively, leaving only a constant number of simple operations for the attribute authority and eligible users to perform locally. In addition, for the first time, we propose an outsourced ABE construction which provides checkability of the outsourced computation results in an efficient way. Extensive security and performance analysis show that the proposed schemes are proven secure and practical. © 2013 IEEE.


Wu N.,Guangdong University of Technology | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
IEEE Transactions on Automation Science and Engineering | Year: 2010

Because of wafer residency time constraints for cluster tools, it is very difficult to schedule them. This paper addresses their scheduling issues and conducts their schedulability and scheduling analysis. A Petri net (PN) model is developed to model them. With this model, to schedule a dual-arm cluster tool with wafer residency time constraints is to determine when and how long the robot should wait for. Based on the model, necessary and sufficient conditions under which the system is schedulable are presented. The conditions can be checked analytically. Meanwhile, an algorithm is developed for the optimal scheduling of dual-arm cluster tools. The algorithm finds an optimal periodic schedule with closed form expressions if it is schedulable. A method is also presented for the implementation of the obtained cyclic schedule by appropriately controlling the initial transient process. Examples are presented to show the application and power of the theory and algorithm. © 2006 IEEE.


Wu N.,Guangdong University of Technology | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
Asian Journal of Control | Year: 2010

In this paper, a colored timed resource-oriented Petri net (CTROPN) is developed to model the cluster tools in semiconductor fabrication. It is structurally simple and concise, since each module in a cluster tool corresponds to a unique place in CTROPN. It is also powerful in modeling the qualitative and temporal behavior of the cluster tools with a single-blade or dual-blade robot. The initial transient behavior, steady-state behavior and the final transient behavior can all be investigated through a single model. © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.


Wang X.,Xidian University | Chen X.,International Institute For Applied Systems Analysis | Wang L.,Peking University
Scientific Reports | Year: 2014

In the Ultimatum Game, two players are offered a chance to win a pie. The proposer suggests how to split the pie. The responder can either accept or reject the deal. If an agreement is not reached, neither player gets anything. Both game theory and evolutionary game theory predict the rational solution that the proposer offers the smallest possible share and the responder accepts it. Fairness thus requires additional mechanisms for natural selection to favor it. Studies to date assumed that individuals have competed for the fixed size of pies, in sharp contrast with real situations, where randomness is ubiquitous. Here we study the impact of random allocation of pies on the evolution of fairness in the Ultimatum Game. Interestingly, we find that the evolution of fairness can be promoted by the randomness associated with the size of pies, without the support of any additional evolutionary mechanisms.


Zheng Y.,Xidian University | Wang L.,Peking University
International Journal of Control | Year: 2014

In this paper, we consider the containment control problem for a group of autonomous agents modelled by heterogeneous dynamics. The communication networks among the leaders and the followers are directed graphs. When the leaders are first-order integrator agents, we present a linear protocol for heterogeneous multi-agent systems such that the second-order integrator agents converge to the convex hull spanned by the first-order integrator agents if and only if the directed graph contains a directed spanning forest. If the leaders are second-order integrator agents, we propose a nonlinear protocol and obtain a necessary and sufficient condition that the heterogeneous multi-agent system solves the containment control problem in finite time. Simulation examples are also provided to illustrate the effectiveness of the theoretical results.© 2013 Taylor & Francis.


Zheng Y.,Xidian University | Zhu Y.,Xidian University | Wang L.,Peking University
International Journal of Systems Science | Year: 2014

This article considers the finite-time consensus of multiple second-order dynamic agents without velocity measurements. A feasible protocol under which each agent can only obtain the measurements of its position relative to its neighbours is proposed. By applying the graph theory, Lyapunov theory and the homogeneous domination method, some sufficient conditions for finite-time consensus of second-order multi-agent systems are established under the different kinds of communication topologies. Some examples are presented to illustrate the effectiveness of the theoretical results. © 2014 Taylor and Francis.


Cong R.,Xidian University | Wu B.,Peking University | Qiu Y.,Xidian University | Wang L.,Xidian University | Wang L.,Peking University
PLoS ONE | Year: 2012

How cooperation emerges and is stabilized has been a puzzling problem to biologists and sociologists since Darwin. One of the possible answers to this problem lies in the mobility patterns. These mobility patterns in previous works are either random-like or driven by payoff-related properties such as fitness, aspiration, or expectation. Here we address another force which drives us to move from place to place: reputation. To this end, we propose a reputation-based model to explore the effect of migration on cooperation in the contest of the prisoner's dilemma. In this model, individuals earn their reputation scores through previous cooperative behaviors. An individual tends to migrate to a new place if he has a neighborhood of low reputation. We show that cooperation is promoted for relatively large population density and not very large temptation to defect. A higher mobility sensitivity to reputation is always better for cooperation. A longer reputation memory favors cooperation, provided that the corresponding mobility sensitivity to reputation is strong enough. The microscopic perception of the effect of this mechanism is also given. Our results may shed some light on the role played by migration in the emergence and persistence of cooperation. © 2012 Cong et al.


Wu N.,Guangdong University of Technology | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
Transactions of the Institute of Measurement and Control | Year: 2011

Considering dynamical changes in manufacturing systems, such as rework and system reconfiguration, this paper presents a new Petri net (PN) model called an intelligent token PN (ITPN). In this model, tokens representing job instances carry real-time knowledge about system status and changes just like smart cards in practice. By taking this advantage, dynamical changes of a system can be easily modelled. An ITPN can model a system in a modular way, leading to a very compact model. When changes occur, it needs to modify only the changed part from the current model. Thus, an ITPN is highly reusable. Based on the ITPN model, a deadlock-free control (DFC) policy is presented. With this control policy, an ITPN is deadlock-free and reversible. In particular, when an ITPN is changed according to the changes of the system, the policy is still applicable to the modified model. Thus, one need not modify the control policy when an ITPN model is modified. © 2011 The Institute of Measurement and Control.


Zheng Y.,Xidian University | Wang L.,Peking University
International Journal of Control | Year: 2012

In this article, we study distributed consensus of heterogeneous multi-agent systems with fixed and switching topologies. The analysis is based on graph theory and nonnegative matrix theory. We propose two kinds of consensus protocols based on the consensus protocol of first-order and second-order multi-agent systems. Some necessary and sufficient conditions that the heterogeneous multi-agent system solves the consensus problems under different consensus protocols are presented with fixed topology. We also give some sufficient conditions for consensus of the heterogeneous multi-agent system with switching topology. Simulation examples are provided to demonstrate the effectiveness of the theoretical results. © 2012 Copyright Taylor and Francis Group, LLC.


Zheng Y.,Xidian University | Wang L.,Peking University
Systems and Control Letters | Year: 2012

This paper studies the finite-time consensus problem of heterogeneous multi-agent systems composed of first-order and second-order integrator agents. By combining the homogeneous domination method with the adding a power integrator method, we propose two classes of consensus protocols with and without velocity measurements. First, we consider the protocol with velocity measurements and prove that it can solve the finite-time consensus under a strongly connected graph and leader-following network, respectively. Second, we consider the finite-time consensus problem of heterogeneous multi-agent systems, for which the second-order integrator agents cannot obtain the velocity measurements for feedback. Finally, some examples are provided to illustrate the effectiveness of the theoretical results. © 2012 Elsevier B.V. All rights reserved.


Zheng Y.,Xidian University | Wang L.,Peking University
International Journal of Control | Year: 2012

This article considers the consensus problem of heterogeneous multi-agent system composed of first-order and second-order agents, in which the second-order integrator agents cannot obtain the velocity (second state) measurements for feedback. Two different consensus protocols are proposed. First, we propose a consensus protocol and discuss the consensus problem of heterogeneous multi-agent system. By applying the graph theory and the Lyapunov direct method, some sufficient conditions for consensus are established when the communication topologies are undirected connected graphs and leader-following networks. Second, due to actuator saturation, we propose another consensus protocol with input constraint and obtain the consensus criterions for heterogeneous multi-agent system. Finally, some examples are presented to illustrate the effectiveness of the obtained criterions. © 2012 Taylor & Francis.


Wu S.-L.,Xidian University | Hsu C.-H.,National Central University
Nonlinearity | Year: 2012

The aim of this work is to study the existence of entire solutions of nonlinear cellular neural networks with distributed time delays (DCNN). The entire solutions are defined in the whole space and for all time t ∈ ℝ. From Yu et al (2011 J. Diff. Eqns 251 630.50), we know that the DCNN model admits travelling front solutions. Combining the travelling front solutions with different wave speeds and a spatially independent solution of the DCNN model, we establish some new entire solutions to describe the interactions of travelling fronts. Various qualitative features of the entire solutions are also investigated in this work. © 2012 IOP Publishing Ltd.


Zhang Q.,Xidian University | Chen Y.,Xidian University | Wang L.,Peking University
Signal Processing | Year: 2013

With three dimensional uniform discrete curvelet transform (3D-UDCT) and spatial-temporal structure tensor, a novel video fusion algorithm for videos with static background images is proposed in this paper. Firstly, the 3D-UDCT is employed to decompose source videos into many subbands with different scales and directions. Secondly, corresponding subbands of source videos are merged with different fusion schemes. Finally, the fused video is obtained by the reverse 3D-UDCT. Especially, when bandpass directional subband coefficients are merged, a spatial-temporal salience detection algorithm based on the structure tensor is performed. And each subband is divided into three types of regions, i.e., regions with temporal moving targets, regions with spatial features of background images, and smooth regions. Then different fusion rules are designed for each type of regions. Compared with some existing fusion methods, the proposed fusion algorithm can not only extract more spatial-temporal salient features from input videos but also perform better in spatial-temporal consistency. In addition, the proposed fusion algorithm can also be extended to fuse videos with dynamic background images by a simple modification. Several sets of experimental results demonstrate the feasibility and validity of the proposed fusion method. © 2013 Elsevier B.V. All rights reserved.


Zheng Y.,Xidian University | Zhu Y.,Xidian University | Wang L.,Peking University
IET Control Theory and Applications | Year: 2011

In this study, the consensus problem of heterogeneous multi-agent system is considered. First, the heterogeneous multi-agent system is proposed which is composed of first-order and second-order integrator agents in two aspects. Then, the consensus problem of heterogeneous multi-agent system is discussed with the linear consensus protocol and the saturated consensus protocol, respectively. By applying the graph theory and Lyapunov direct method, some sufficient conditions for consensus are established when the communication topologies are undirected connected graphs and leader-following networks. Finally, some examples are presented to illustrate the theoretical results. © 2011 The Institution of Engineering and Technology.


Wang B.,Xidian University | Chen X.,International Institute For Applied Systems Analysis | Wang L.,Peking University
Journal of Statistical Mechanics: Theory and Experiment | Year: 2012

Most previous works study the evolution of cooperation in a structured population by commonly employing an isolated single network. However, realistic systems are composed of many interdependent networks coupled with each other, rather than an isolated single one. In this paper, we consider a system including two interacting networks with the same size, entangled with each other by the introduction of probabilistic interconnections. We introduce the public goods game into such a system, and study how the probabilistic interconnection influences the evolution of cooperation of the whole system and the coupling effect between two layers of interdependent networks. Simulation results show that there exists an intermediate region of interconnection probability leading to the maximum cooperation level in the whole system. Interestingly, we find that at the optimal interconnection probability the fraction of internal links between cooperators in two layers is maximal. Also, even if initially there are no cooperators in one layer of interdependent networks, cooperation can still be promoted by probabilistic interconnection, and the cooperation levels in both layers can more easily reach an agreement at the intermediate interconnection probability. Our results may be helpful in understanding cooperative behavior in some realistic interdependent networks and thus highlight the importance of probabilistic interconnection on the evolution of cooperation. © 2012 IOP Publishing Ltd and SISSA Medialab srl.


Zhang S.,Xidian University | Gao F.,Tsinghua National Laboratory for Information Sciences and Technology | Gao F.,Nanjing Southeast University | Gao F.,Jacobs University Bremen | Pei C.-X.,Xidian University
IEEE Transactions on Signal Processing | Year: 2012

This correspondence considers the optimal training design in a classical three-node amplify-and-forward two-way relay network (TWRN) that targets at estimating the individual channel between each source node and the relay node. The transmission environment is assumed to be frequency selective and the orthogonal-frequency-division multiplexing (OFDM) modulation is adopted. We derive the Bayesian Cramér-Rao bound (CRB) for the individual channel estimation, from which the optimal training is obtained. Extensive numerical results are provided to corroborate the proposed studies. © 1991-2012 IEEE.


Wang Y.,Shanghai JiaoTong University | Wang Y.,Xidian University | Chen W.,Shanghai JiaoTong University | Chen W.,China Mobile | Tellambura C.,University of Alberta
IEEE Transactions on Wireless Communications | Year: 2010

One of the major drawbacks of orthogonal frequency division multiplexing (OFDM) signals is the high peak to average power ratio (PAPR) of the transmitted signal. Many PAPR reduction techniques have been proposed in the literature, among which, partial transmit sequence (PTS) technique has been taken considerable investigation. However, PTS technique requires an exhaustive search over all combinations of allowed phase factors, whose complexity increases exponentially with the number of sub-blocks. In this paper, a newly suboptimal method based on modified artificial bee colony (ABC-PTS) algorithm is proposed to search the better combination of phase factors. The ABC-PTS algorithm can significantly reduce the computational complexity for larger PTS subblocks and offers lower PAPR at the same time. Simulation results show that the ABC-PTS algorithm is an efficient method to achieve significant PAPR reduction. © 2010 IEEE.


Gao L.,Shanghai JiaoTong University | Gao L.,Xidian University | Xu Y.,Shanghai JiaoTong University | Wang X.,Shanghai JiaoTong University
IEEE Transactions on Mobile Computing | Year: 2011

Cognitive radio (CR) is a promising paradigm to achieve efficient utilization of the limited spectrum resource by allowing the unlicensed users to access the licensed spectrum, and dynamic spectrum access (DSA) is one of the fundamental functions of CR networks. Market-driven spectrum auction has been recognized as an effective way to achieve DSA. In spectrum auction, the primary spectrum owners (POs) act as auctioneers who are willing to sell idle spectrum bands for additional revenue, and the secondary users (SUs) act as bidders who are willing to buy spectrum bands from POs for their services. However, conventional spectrum auction designs are restricted within the scenario of single auctioneer. In this paper, we study the spectrum auction with multiple auctioneers and multiple bidders, which is more realistic for practical CR networks. We propose MAP, a Multiauctioneer Progressive auction mechanism, in which each auctioneer systematically raises the trading price and each bidder subsequently chooses one auctioneer for bidding. The equilibrium is defined as the state that no auctioneer and bidder would like to change his decision. We show analytically that MAP converges to the equilibrium with maximum spectrum utilization of the whole system. We further analyze the incentive for POs and SUs joining the auction and accepting the auction result. Simulation results show that MAP well converges to the equilibrium, and the spectrum utilization is arbitrary closed to the global optimal solution according to the length of step. © 2011 IEEE.


Wei L.,Shanghai JiaoTong University | Chen W.,Shanghai JiaoTong University | Chen W.,Xidian University
IEEE Transactions on Wireless Communications | Year: 2012

Network coding is a new and promising paradigm for modern communication networks by allowing intermediate nodes to mix messages received from multiple sources. Compute-and-forward strategy is one category of network coding in which a relay will decode and forward a linear combination of source messages according to the observed channel coefficients, based on the algebraic structure of lattice codes. The destination will recover all transmitted messages if enough linear equations are received. In this work, we design in a system level, the compute-and-forward network coding coefficients by Fincke-Pohst based candidate set searching algorithm and network coding system matrix constructing algorithm, such that by those proposed algorithms, the transmission rate of the multi-source multi-relay system is maximized. Numerical results demonstrate the effectiveness of our proposed algorithms. © 2012 IEEE.


Wei L.,Shanghai JiaoTong University | Chen W.,Shanghai JiaoTong University | Chen W.,Xidian University
IEEE Communications Letters | Year: 2012

We consider the two-way relay channel (TWRC) with compute-and-forward network coding strategy. First a new lemma is proposed as network codes search criteria for TWRC. Then, instead of exhaustive search, we present an efficient network codes search algorithm based on modified Fincke-Pohst method. Numerical results demonstrate the effectiveness and complexity reduction of our proposed lemma and algorithm. © 1997-2012 IEEE.


Gao F.,Beijing University of Posts and Telecommunications | Gao F.,Xidian University | Liu B.,Beijing University of Posts and Telecommunications | Wen Q.-Y.,Beijing University of Posts and Telecommunications | Chen H.,Science and Technology on Communication Security Laboratory
Optics Express | Year: 2012

By adding a parameter θ in M. Jakobi et al's protocol [Phys. Rev. A 83, 022301 (2011)], we present a flexible quantum-key-distributionbased protocol for quantum private queries. We show that, by adjusting the value of θ, the average number of the key bits Alice obtains can be located on any fixed value the users wanted for any database size. And the parameter k is generally smaller (even k = 1 can be achieved) when θ < π/4, which implies lower complexity of both quantum and classical communications. Furthermore, the users can choose a smaller θ to get better database security, or a larger θ to obtain a lower probability with which Bob can correctly guess the address of Alice's query. © 2012 Optical Society of America.


Du L.,Xidian University | Wang P.,Xidian University | Liu H.,Xidian University | Pan M.,Xidian University | And 2 more authors.
IEEE Transactions on Signal Processing | Year: 2011

A Bayesian dynamic model based on multitask learning (MTL) is developed for radar automatic target recognition (RATR) using high-resolution range profile (HRRP). The aspect-dependent HRRP sequence is modeled using a truncated stick-breaking hidden Markov model (TSB-HMM) with time-evolving transition probabilities, in which the spatial structure across range cells is described by the hidden Markov structure and the temporal dependence between HRRP samples is described by the time evolution of the transition probabilities. This framework imposes the belief that temporally proximate HRRPs are more likely to be drawn from similar HMMs, while also allowing for possible distant repetition or innovation. In addition, as formulated the stick-breaking prior and MTL mechanism are employed to infer the number of hidden states in an HMM and learn the target-dependent states collectively for all targets. The form of the proposed hierarchical model allows efficient variational Bayesian (VB) inference, of interest for large-scale problems. To validate the formulation, example results are presented for an illustrative synthesized dataset and our main application-RATR, for which we consider the measured HRRP data. For the latter, we also make comparisons to the model with the independent state-transition statistics and some other existing statistical models for radar HRRP data. © 2011 IEEE.


Wang Y.,Shanghai JiaoTong University | Chen W.,Shanghai JiaoTong University | Chen W.,Xidian University | Tellambura C.,University of Alberta
IEEE Transactions on Broadcasting | Year: 2012

In tone reservation (TR) based OFDM systems, the peak to average power ratio (PAPR) reduction performance mainly depends on the selection of the peak reduction tone (PRT) set and the optimal target clipping level. Finding the optimal PRT set requires an exhaustive search of all combinations of possible PRT sets, which is a nondeterministic polynomial-time (NP-hard) problem, and this search is infeasible for the number of tones used in practical systems. The existing selection methods, such as the consecutive PRT set, equally spaced PRT set and random PRT set, perform poorly compared to the optimal PRT set or incur high computational complexity. In this paper, an efficient scheme based on genetic algorithm (GA) with lower computational complexity is proposed for searching a nearly optimal PRT set. While TR-based clipping is simple and attractive for practical implementation, determining the optimal target clipping level is difficult. To overcome this problem, we propose an adaptive clipping control algorithm. Simulation results show that our proposed algorithms efficiently obtain a nearly optimal PRT set and good PAPR reductions. © 2012 IEEE.


Yang Y.-G.,Beijing University of Technology | Yang Y.-G.,Xidian University | Xia J.,Beijing University of Technology | Jia X.,Beijing University of Technology | Zhang H.,Beijing University of Posts and Telecommunications
Quantum Information Processing | Year: 2013

As an important branch of quantum cryptography, quantum private comparison (QPC) has recently received a lot of attention. In this paper we study the security of previous QPC protocols with a semi-honest third party (TP) from the viewpoint of secure multi-party computation and show that the assumption of a semi-honest TP is unreasonable. Without the unreasonable assumption of a semi-honest TP, one can easily find that the QPC protocol (Tseng et al. in Quantum Inf Process, 2011, doi: 10.1007/s11128-011-0251-0) has an obvious security flaw. Some suggestions about the design of QPC protocols are also given. © 2012 Springer Science+Business Media, LLC.


Wan H.,Shanghai JiaoTong University | Wan H.,Guangxi University | Chen W.,Shanghai JiaoTong University | Chen W.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2012

In this paper, we investigate joint source precoding matrices and relay processing matrix design for multiuser multiple-input-multiple-output (MIMO) nonregenerative relay networks in the presence of the direct source-destination links. We consider both capacity and mean-square-error (MSE) criteria subject to the distributed power constraints, which are nonconvex and apparently have no simple solutions. Therefore, we propose an optimal source precoding matrix structure based on the point-to-point MIMO channel technique and a new relay processing matrix structure under the modified power constraint at relay node, based on which a nested iterative algorithm of jointly optimizing sources precoding and relay processing is established. We show that the capacity-based optimal source precoding matrices share the same structure with the MSE-based matrices and so does the optimal relay processing matrix. Simulation results demonstrate that the proposed algorithm outperforms the existing results. © 1967-2012 IEEE.


Liu Y.,Shanghai JiaoTong University | Liu Y.,Xidian University | Chen W.,Shanghai JiaoTong University | Chen W.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2012

A limited-feedback-based dynamic resource allocation algorithm is proposed for a relay cooperative network with orthogonal frequency-division-multiplexing (OFDM) modulation. A communication model where one source node communicates with one destination node assisted by one half-duplex decode-and-forward (DF) relay is considered in this paper. We first consider the selective DF scheme, in which some relay subcarriers will keep idle if they do not have the advantage of forwarding the received symbols. Furthermore, we consider the enhanced DF scheme where the idle subcarriers are used to transmit new messages at the source. We aim to maximize the system's instantaneous rate by jointly optimizing power allocation and subcarrier pairing on each subcarrier based on the Lloyd algorithm. Both sum and individual power constraints are considered. The joint optimization turns out to be a mixed integer programming problem. We then transform it into a convex optimization by continuous relaxation and achieve the solution in the dual domain. The performance of the proposed joint resource allocation algorithm is verified by simulations. We find that the proposed scheme outperforms the existing methods in various channel conditions. We also observe that only a few feedback bits can achieve most of the performance gain of the perfect channel-state-information (CSI)-based resource allocation algorithm at different levels of signal-to-noise ratio (SNR). © 2012 IEEE.


Huang J.,Xidian University | Sun H.,Xi'an University of Science and Technology | Liu Y.,Xidian University | Song Q.,Xi'an University of Science and Technology | Weninger T.,University of Illinois at Urbana - Champaign
PLoS ONE | Year: 2011

The investigation of community structure in networks has aroused great interest in multiple disciplines. One of the challenges is to find local communities from a starting vertex in a network without global information about the entire network. Many existing methods tend to be accurate depending on a priori assumptions of network properties and predefined parameters. In this paper, we introduce a new quality function of local community and present a fast local expansion algorithm for uncovering communities in large-scale networks. The proposed algorithm can detect multiresolution community from a source vertex or communities covering the whole network. Experimental results show that the proposed algorithm is efficient and well-behaved in both real-world and synthetic networks. © 2011 Huang et al.


Wang X.,Shanghai JiaoTong University | Li Z.,Shanghai JiaoTong University | Xu P.,Shanghai JiaoTong University | Xu Y.,Shanghai JiaoTong University | And 2 more authors.
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2010

Cognitive radio is emerging as a promising technique to improve the utilization of the radio frequency spectrum. In this paper, we consider the problem of spectrum sharing among primary (or "licensed") users (PUs) and secondary (or "unlicensed") users (SUs). We formulate the problem based on bandwidth auction, in which each SU makes a bid for the amount of spectrum and each PU may assign the spectrum among the SUs by itself according to the information from the SUs without degrading its own performance. We show that the auction is a noncooperative game and that Nash equilibrium (NE) can be its solution. We first consider a single-PU network to investigate the existence and uniqueness of the NE and further discuss the fairness among the SUs under given conditions. Then, we present a dynamic updating algorithm in which each SU achieves NE in a distributed manner. The stability condition of the dynamic behavior for this spectrum-sharing scheme is studied. The discussion is generalized to the case in which there are multiple PUs in the network, where the properties of the NE are shown under appropriate conditions. Simulations were used to evaluate the system performance and verify the effectiveness of the proposed algorithm. © 2006 IEEE.


Wang G.,University of Alberta | Gao F.,Tsinghua University | Gao F.,Jacobs Engineering | Chen W.,Shanghai JiaoTong University | And 2 more authors.
IEEE Transactions on Wireless Communications | Year: 2011

In this paper, channel estimation and training sequence design are considered for amplify-and-forward (AF)-based two-way relay networks (TWRNs) in a time-selective fading environment. A new complex-exponential basis expansion model (CE-BEM) is proposed to represent the mobile-to-mobile time-varying channels. To estimate such channels, a novel pilot symbol-aided transmission scheme is developed such that a low complex linear approach can estimate the BEM coefficients of the convoluted channels. More essentially, two algorithms are designed to extract the BEM coefficients of the individual channels. The optimal training parameters, including the number of the pilot symbols, the placement of the pilot symbols, and the power allocation to the pilot symbols, are derived by minimizing the channel mean-square error (MSE). The selections of the system parameters are thoroughly discussed in order to guide practical system design. Finally, extensive numerical results are provided to corroborate the proposed studies. © 2006 IEEE.


Shi Y.,Xidian University | Shi Y.,University of Illinois at Urbana - Champaign | Jin J.-M.,University of Illinois at Urbana - Champaign
IEEE Transactions on Antennas and Propagation | Year: 2011

A marching-on-in-degree (MOD)-based scheme for analyzing transient electromagnetic scattering from three-dimensional dispersive dielectric objects is proposed. A time-domain volume integral equation (TDVIE) for the electric flux density throughout the object is first formulated and then solved using the MOD scheme. With the use of weighted Laguerre polynomials as entire-domain temporal basis functions, the convolution of the electric flux density and the medium susceptibility and its derivatives can be handled analytically. By employing the Galerkin temporal testing procedure, the time variable is eliminated in the resultant recursive matrix equation so that the proposed algorithm overcomes the late-time instability problem that may occur in the conventional marching-on-in-time (MOT) approach. Some complex dispersive media, such as the Debye, Lorentz, and Drude media, are simulated to illustrate the validity of the TDVIE-MOD algorithm. © 2010 IEEE.


Shi Y.,Xidian University | Jin J.-M.,University of Illinois at Urbana - Champaign
IEEE Antennas and Wireless Propagation Letters | Year: 2011

A higher-order Nystrm scheme is developed for the marching-on-in-degree (MOD) solution of the time-domain magnetic field integral equation (TDMFIE) for the analysis of transient electromagentic scattering from a three-dimensional closed conducting object of arbitrary shape. In this method, the surface of the object is discretized into curvilinear triangular patches and the Lagrange interpolation polynomials are utilized to expand the spatial variation of the unknown electric current density in the TDMFIE. The transient variation of the electric current density is expanded in terms of the weighted Laguerre polynomials. With the use of the point-matching spatial and Galerkin temporal testing procedures, the proposed algorithm overcomes the late-time instability problem that often occurs in the marching-on-in-time (MOT) approach. Numerical results are presented to show that the proposed algorithm exhibits a good accuracy, a highly efficient computation of the impedance matrices, and a higher-order convergence with regard to the spatial discretization. © 2011 IEEE.


Chen X.,Xidian University | Li J.,Guangzhou University | Susilo W.,University of Wollongong
IEEE Transactions on Information Forensics and Security | Year: 2012

The outsourcing computations in distributed environments suffer from the trust problems between the outsourcer and the workers. All existing solutions only assume the rational lazy-but-honest workers. In this paper, we first introduce the rational lazy-and-partially-dishonest workers in the outsourcing computation model. In addition, we propose a new fair conditional payment scheme for outsourcing computation that is only based on traditional electronic cash systems. The proposed construction uses a semitrusted third party T to achieve the fairness and efficiency. However, T is only involved in the protocol in the exceptional case, namely in the case of disputes. Moreover, since neither the secret sharing/splitting scheme nor the cut-and-choose protocol is used for the generation or verification of the payment token, our solution clearly outperforms the existing schemes in terms of efficiency. © 2005-2012 IEEE.


Guo T.,Anyang University, China | Zhang J.,Xidian University
Yi Qi Yi Biao Xue Bao/Chinese Journal of Scientific Instrument | Year: 2011

An adaptive fuzzy dynamic surface control approach is proposed for the control problem of unknown nonlinear systems with completely unknown time delays. The unknown delay functions are approximated with fuzzy logic systems, and then the delay signals in the inputs of approximators are replaced by reference signals, so that the common assumptions on the delay signals are removed, and the dependency to time delay assumptions that traditional design needs is got rid of. Adaptive bounding technique is used to deal with the fuzzy approximation errors and delay replacement errors. Based on Lyapunov-Krasovskii functional, all the signals of the closed-loop system are proven to be semi-globally uniformly ultimately bounded; and arbitrary output tracking accuracy is guaranteed by tuning the design parameters. The effectiveness of the proposed control approach is verified with simulation results.


Gao F.,Beijing University of Posts and Telecommunications | Gao F.,Xidian University | Qin S.-J.,Beijing University of Posts and Telecommunications | Guo F.-Z.,Beijing University of Posts and Telecommunications | Wen Q.-Y.,Beijing University of Posts and Telecommunications
Physical Review A - Atomic, Molecular, and Optical Physics | Year: 2011

As a new model for signing quantum messages, arbitrated quantum signature (AQS) has recently received a lot of attention. In this paper we study the cryptanalysis of previous AQS protocols from the aspects of forgery and disavowal. We show that in these protocols the receiver, Bob, can realize existential forgery of the sender's signature under known message attack. Bob can even achieve universal forgery when the protocols are used to sign a classical message. Furthermore, the sender, Alice, can successfully disavow any of her signatures by simple attack. The attack strategies are described in detail and some discussions about the potential improvements of the protocols are given. Finally we also present several interesting topics on AQS protocols that can be studied in future. © 2011 American Physical Society.


Stratulat S.M.,Max Planck Institute of Microstructure Physics | Stratulat S.M.,Al. I. Cuza University | Lu X.,Max Planck Institute of Microstructure Physics | Lu X.,Xidian University | And 5 more authors.
Nano Letters | Year: 2013

Large areas of perfectly ordered magnetic CoFe2O4 nanopillars embedded in a ferroelectric BiFeO3 matrix were successfully fabricated via a novel nucleation-induced self-assembly process. The nucleation centers of the magnetic pillars are induced before the growth of the composite structure using anodic aluminum oxide (AAO) and lithography-defined gold membranes as hard mask. High structural quality and good functional properties were obtained. Magneto-capacitance data revealed extremely low losses and magneto-electric coupling of about 0.9 μC/cmOe. The present fabrication process might be relevant for inducing ordering in systems based on phase separation, as the nucleation and growth is a rather general feature of these systems. © 2013 American Chemical Society.


Yuan Q.,Sendai National College of Technology | Chen Q.,Tohoku University | Li L.,Xidian University | Sawaya K.,Tohoku University
IEEE Transactions on Antennas and Propagation | Year: 2010

A practical wireless power transmission system consisting of a large rectangular wire loop and a small square wire loop with a parasitic square helical coil is proposed for use as an efficient evanescent resonant coupling wireless power transmission system in an indoor environment. In addition, a full wave-based numerical analysis on the resonant frequency of and the power transmission efficiency of wireless power transmission system are performed in this paper. The effects of the following on power transmission efficiency and the resonant frequency are numerically investigated: The load of the receiving element and the presence of non-resonant objects such as a conducting box or human body. The numerical results show that a power transmission efficiency of nearly 50% can be achieved when the proposed system is used to charge only one user with the optimized load. The results also show that power transmission efficiency is reduced significantly when a human body is in very close proximity to the receiving element. This reduction in efficiency can be alleviated significantly, however, if the relative distance between the receiving element and the human body is greater than 0.5 m or 0.03λ at a resonant frequency of 19.22 MHz. © 2006 IEEE.


Yan Z.,Xidian University | Yan Z.,Aalto University | Zhang P.,Applied Technology Internet | Vasilakos A.V.,Kuwait University
Journal of Network and Computer Applications | Year: 2014

Internet of Things (IoT) is going to create a world where physical objects are seamlessly integrated into information networks in order to provide advanced and intelligent services for human-beings. Trust management plays an important role in IoT for reliable data fusion and mining, qualified services with context-awareness, and enhanced user privacy and information security. It helps people overcome perceptions of uncertainty and risk and engages in user acceptance and consumption on IoT services and applications. However, current literature still lacks a comprehensive study on trust management in IoT. In this paper, we investigate the properties of trust, propose objectives of IoT trust management, and provide a survey on the current literature advances towards trustworthy IoT. Furthermore, we discuss unsolved issues, specify research challenges and indicate future research trends by proposing a research model for holistic trust management in IoT. © 2014 Elsevier Ltd.


Tian C.,Xidian University | Fan G.,Oklahoma State University | Gao X.,Xidian University | Tian Q.,University of Texas at San Antonio
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2012

Face images under uncontrolled environments suffer from the changes of multiple factors such as camera view, illumination, expression, etc. Tensor analysis provides a way of analyzing the influence of different factors on facial variation. However, the TensorFace model creates a difficulty in representing the nonlinearity of view subspace. In this paper, to break this limitation, we present a view-manifold-based TensorFace (V-TensorFace), in which the latent view manifold preserves the local distances in the multiview face space. Moreover, a kernelized TensorFace (K-TensorFace) for multiview face recognition is proposed to preserve the structure of the latent manifold in the image space. Both methods provide a generative model that involves a continuous view manifold for unseen view representation. Most importantly, we propose a unified framework to generalize TensorFace, V-TensorFace, and K-TensorFace. Finally, an expectation-maximization like algorithm is developed to estimate the identity and view parameters iteratively for a face image of an unknown/unseen view. The experiment on the PIE database shows the effectiveness of the manifold construction method. Extensive comparison experiments on Weizmann and Oriental Face databases for multiview face recognition demonstrate the superiority of the proposed V- and K-TensorFace methods over the view-based principal component analysis and other state-of-the-art approaches for such purpose. © 2006 IEEE.


Feng X.,Xidian University | Elden L.,Linköping University
Inverse Problems | Year: 2014

An ill-posed Cauchy problem for a 3D elliptic partial differential equation with variable coefficients is considered. A well-posed quasi-boundary-value (QBV) problem is given to approximate it. Some stability estimates are given. For the numerical implementation, a large sparse system is obtained from discretizing the QBV problem using the finite difference method. A left-preconditioned generalized minimum residual method is used to solve the large system effectively. For the preconditioned system, a fast solver using the fast Fourier transform is given. Numerical results show that the method works well. © 2014 IOP Publishing Ltd.


Xie J.,Xidian University | Xie J.,Shaanxi Normal University | Wang C.,Shaanxi Normal University | Wang C.,Gansu Institute of Mechanical and Electrical
Expert Systems with Applications | Year: 2011

In this paper, we developed a diagnosis model based on support vector machines (SVM) with a novel hybrid feature selection method to diagnose erythemato-squamous diseases. Our proposed hybrid feature selection method, named improved F-score and Sequential Forward Search (IFSFS), combines the advantages of filter and wrapper methods to select the optimal feature subset from the original feature set. In our IFSFS, we improved the original F-score from measuring the discrimination of two sets of real numbers to measuring the discrimination between more than two sets of real numbers. The improved F-score and Sequential Forward Search (SFS) are combined to find the optimal feature subset in the process of feature selection, where, the improved F-score is an evaluation criterion of filter method, and SFS is an evaluation system of wrapper method. The best parameters of kernel function of SVM are found out by grid search technique. Experiments have been conducted on different training-test partitions of the erythemato-squamous diseases dataset taken from UCI (University of California Irvine) machine learning database. Our experimental results show that the proposed SVM-based model with IFSFS achieves 98.61% classification accuracy and contains 21 features. With these results, we conclude our method is very promising compared to the previously reported results. © 2010 Elsevier Ltd. All rights reserved.


Duan Z.,Xidian University | Zhang N.,Xidian University | Koutny M.,Newcastle University
Theoretical Computer Science | Year: 2013

The paper presents a proof system for Propositional Projection Temporal Logic (PPTL) with projection-plus. The syntax, semantics, and logical laws of PPTL are introduced together with an axiom system consisting of axioms and inference rules. To facilitate proofs, some of the frequently used theorems are proved. A normal form of PPTL formulas is presented, and the soundness and completeness of the proof system are demonstrated. To show how the axiom system works, a full omega regular property for the mutual exclusion problem is specified by a PPTL formula and then a deductive proof of the property is performed. © 2012 Elsevier B.V. All rights reserved.


Xiao B.,Xidian University | Xiao B.,Ningxia University | Ma J.-F.,Xidian University | Wang X.,Shaanxi Normal University
Pattern Recognition | Year: 2010

In this paper, we proposed a new set of moments based on the Bessel function of the first kind, named Bessel-Fourier moments (BFMs), which are more suitable than orthogonal Fourier-Mellin and Zernike moments for image analysis and rotation invariant pattern recognition. Compared with orthogonal Fourier-Mellin and Zernike polynomials of the same degree, the new orthogonal radial polynomials have more zeros, and these zeros are more evenly distributed. The Bessel-Fourier moments can be thought of as generalized orthogonalized complex moments. Theoretical and experimental results show that the Bessel-Fourier moments perform better than the orthogonal Fourier-Mellin and Zernike moments (OFMMs and ZMs) in terms of image reconstruction capability and invariant recognition accuracy in noise-free, noisy and smooth distortion conditions. © 2010 Elsevier Ltd. All rights reserved.


Xu H.-X.,PLA Air Force Aviation University | Wang G.-M.,PLA Air Force Aviation University | Qi M.-Q.,Nanjing Southeast University | Liang J.-G.,PLA Air Force Aviation University | And 2 more authors.
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

We report on the design, fabrication, and measurement of a triple-band absorber enhanced from a planar two-dimensional artificial metamaterial transmission line (TL) concept. Unlike previous multiband absorbers, this implementation incorporates fractal geometry into the artificial TL framework. As a consequence of the formed large LC values, the utilized element is compact in size, which approaches λ 0/15 at the lowest fundamental resonant frequency. For independent control and design, a theoretical characterization based on a circuit model analysis (TL theory) is performed and a set of design procedures is also derived. Both numerical and experimental results have validated three strong absorption peaks across the S, C, and X bands, respectively, which are attributable to a series of self-resonances induced in the specific localized area. The absorber features near-unity absorption for a wide range of incident angles and polarization states and a great degree of design flexibility by manipulating the LC values in a straightforward way. © 2012 American Physical Society.


Cheng W.,Xidian University | Zhang X.,Texas A&M University | Zhang X.,Nanjing Southeast University | Zhang H.,Xidian University
IEEE Journal on Selected Areas in Communications | Year: 2013

To enable multiple mobile users to transmit their signals simultaneously over the same sub-channels, the virtual multiple-input multiple-output (V-MIMO) techniques can exploit the multiple-input multiple-output (MIMO) spectrum efficiency gain. Traditional V-MIMO transmission schemes mainly focus on maximizing the throughput of grouped mobile users without taking into account the quality-of-service (QoS) provisionings. In this paper, we propose the optimal power allocation schemes with statistical QoS provisionings to maximize the effective capacity of non-collaborative/collaborative V-MIMO wireless networks, respectively. For non-collaborative V-MIMO wireless networks, the mobile users in one V-MIMO group transmit signals independently over the same sub-channels. In the view point of existing mobile users, they solely occupy the sub-channels. Thus, the existing mobile users employ the QoS-driven single-user power allocation scheme to maximize their effective capacity. By converting the non-collaborative V-MIMO transmission optimization problem into a strictly convex optimization problem, we derive the QoS-driven power allocation scheme for the newly added mobile users to maximize their effective capacity. For collaborative V-MIMO wireless networks where the mobile users in one group can collaboratively transmit their signals, we derive the QoS-driven collaborative power allocation schemes for both the existing and the newly added mobile users. Also conducted is a set of simulation evaluations, showing that our proposed power allocation schemes for V-MIMO wireless networks outperform the other existing schemes. © 2013 IEEE.


Zuo S.-L.,Xidian University | Wu W.-J.,China Ship Development And Design Center | Zhang Z.-Y.,Xidian University
Progress in Electromagnetics Research Letters | Year: 2013

This paper presents a simple microstrip filtering-antenna with compact size for WLAN application. The T-shape resonator through an inset coupling structure can be treated as the admittance inverter and the equivalent circuit of the filtering-antenna is exactly the same as the bandpass filter prototype. With a little extra circuit area, the proposed filtering-antenna has almost twice wider bandwidth, good skirt selectivity and high suppression in the stopband compared to the conventional microstrip antenna.


Liu H.,Shaanxi Normal University | Zhao F.,University of Posts and Telecommunications | Jiao L.,Xidian University
Applied Soft Computing Journal | Year: 2012

In recent years, spectral clustering has become one of the most popular clustering algorithms in areas of pattern analysis and recognition. This algorithm uses the eigenvalues and eigenvectors of a normalized similarity matrix to partition the data, and is simple to implement. However, when the image is corrupted by noise, spectral clustering cannot obtain satisfying segmentation performance. In order to overcome the noise sensitivity of the standard spectral clustering algorithm, a novel fuzzy spectral clustering algorithm with robust spatial information for image segmentation (FSC-RS) is proposed in this paper. Firstly, a non-local-weighted sum image of the original image is generated by utilizing the pixels with a similar configuration of each pixel. Then a robust gray-based fuzzy similarity measure is defined by using the fuzzy membership values among gray values in the new generated image. Thus, the similarity matrix obtained by this measure is only dependent on the number of the gray-levels and can be easily stored. Finally, the spectral graph partitioning method can be applied to this similarity matrix to group the gray values of the new generated image and then the corresponding pixels in the image are reclassified to obtain the final segmentation result. Some segmentation experiments on synthetic and real images show that the proposed method outperforms traditional spectral clustering methods and spatial fuzzy clustering in efficiency and robustness. © 2012 Elsevier B.V. All rights reserved.


Wang C.,Xi'an Jiaotong University | Wang H.-M.,Nanjing Southeast University | Xia X.-G.,Xidian University | Xia X.-G.,University of Delaware
IEEE Transactions on Wireless Communications | Year: 2015

This paper studies the cooperative transmission for securing a decode-and-forward (DF) two-hop network where multiple cooperative nodes coexist with a potential eavesdropper. Under the more practical assumption that only the channel distribution information (CDI) of the eavesdropper is known, we propose an opportunistic relaying with artificial jamming secrecy scheme, where a 'best' cooperative node is chosen among a collection of N possible candidates to forward the confidential signal and the others send jamming signals to confuse the eavesdroppers. We first investigate the ergodic secrecy rate (ESR) maximization problem by optimizing the power allocation between the confidential signal and jamming signals. In particular, we exploit the limiting distribution technique of extreme order statistics to build an asymptotic closed-form expression of the achievable ESR and the power allocation is optimized to maximize the ESR lower bound. Although the optimization problems are non-convex, we propose a sequential parametric convex approximation (SPCA) algorithm to locate the Karush-Kuhn-Tucker (KKT) solutions. Furthermore, taking the time variance of the legitimate links' CSIs into consideration, we address the impacts of the outdated CSIs to the proposed secrecy scheme, and derive an asymptotic ESR. Finally, we generalize the analysis to the scenario with multiple eavesdroppers, and give the asymptotic analytical results of the achievable ESR. Simulation results confirm our analytical results. © 2002-2012 IEEE.


Liu J.,Stevens Institute of Technology | Liu J.,Xidian University | Li H.,Stevens Institute of Technology | Himed B.,U.S. Air force
IEEE Transactions on Signal Processing | Year: 2014

This paper considers the problem of passive detection with a multistatic radar system involving a noncooperative illuminator of opportunity (IO) and multiple receive platforms. An unknown source signal is transmitted by the IO, which illuminates a target of interest. These receive platforms are geographically dispersed, and collect independent target echoes due to the illumination by the same IO. We consider a generalized canonical correlation (GCC) detector for passive detection which requires the knowledge of the noise power. We derive closed-form expressions for the probabilities of false alarm and detection of this detector. For the case where the noise power is unknown, we propose a generalized likelihood ratio test (GLRT) detector to deal with the passive detection problem. Moreover, a closed-form expression for the probability of false alarm of this GLRT detector is given, which shows that the proposed GLRT detector exhibits a constant false alarm rate property with respect to the noise power. Numerical simulations demonstrate that the proposed GLRT detector generally outperforms the generalized coherence detector, a previous popular passive detector that neither requires the knowledge of the noise power. In addition, the GLRT also outperforms the GCC detector when the latter has an uncertainty in its knowledge of the noise power. © 2014 IEEE.


Ling Q.,Anhui University of Science and Technology | Ling Q.,Xidian University | Ribeiro A.,University of Pennsylvania
IEEE Transactions on Signal Processing | Year: 2014

This paper develops the application of the alternating direction method of multipliers (ADMM) to optimize a dynamic objective function in a decentralized multi-agent system. At each time slot, agents in the network observe local functions and cooperate to track the optimal time-varying argument of the sum objective. This cooperation is based on maintaining local primal variables that estimate the value of the optimal argument and auxiliary dual variables that encourage proximity with neighboring estimates. Primal and dual variables are updated by an ADMM iteration that can be implemented in a distributed manner whereby local updates require access to local variables and the most recent primal variables from adjacent agents. For objective functions that are strongly convex and have Lipschitz continuous gradients, the distances between the primal and dual iterates to their corresponding time-varying optimal values are shown to converge to a steady state gap. This gap is explicitly characterized in terms of the condition number of the objective function, the condition number of the network that is defined as the ratio between the largest and smallest nonzero Laplacian eigenvalues, and a bound on the drifts of the optimal primal variables and the optimal gradients. Numerical experiments corroborate theoretical findings and show that the results also hold for non-differentiable and non-strongly convex primal objectives. © 2013 IEEE.


Hu R.,Xidian University | Wang L.,Beihang University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2014

In this paper, we study the dynamics of freely falling plates based on the Kirchhoff equation and the quasisteady aerodynamic model. Motion transitions among fluttering, tumbling along a cusp-like trajectory, irregular, and tumbling along a straight trajectory are obtained by solving the dynamical equations. Phase diagrams spanning between the nondimensional moment of inertia and aerodynamic coefficients or aspect ratio are built to identify regimes for these falling styles. We also investigate the stability of fixed points and bifurcation scenarios. It is found that the transitions are all heteroclinic bifurcations and the influence of the fixed-point stability is local. © 2014 American Physical Society.


Zhou Z.,Southwest Jiaotong University | Zhou Z.,Xidian University | Ding C.,Hong Kong University of Science and Technology | Luo J.,University of Bergen | Zhang A.,Xi'an University of Technology
IEEE Transactions on Information Theory | Year: 2013

Cyclic codes are a subclass of linear codes and have applications in consumer electronics, data storage systems, and communication systems as they have efficient encoding and decoding algorithms. In this paper, a family of $p$-ary cyclic codes whose duals have three pairwise nonconjugate zeros is proposed. The weight distribution of this family of cyclic codes is determined. It turns out that the proposed cyclic codes have five nonzero weights. © 1963-2012 IEEE.


Niu Z.,Xidian University | Hua G.,Stevens Institute of Technology | Gao X.,Xidian University | Tian Q.,University of Texas at San Antonio
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2012

We present a discriminative latent topic model for scene recognition. The capacity of our model is originated from the modeling of two types of visual contexts, i.e., the category specific global spatial layout of different scene elements, and the reinforcement of the visual coherence in uniform local regions. In contrast, most previous methods for scene recognition either only modeled one of these two visual contexts, or just totally ignored both of them. We cast these two coupled visual contexts in a discriminative Latent Dirichlet Allocation framework, namely context aware topic model. Then scene recognition is achieved by Bayesian inference given a target image. Our experiments on several scene recognition benchmarks clearly demonstrated the advantages of the proposed model. © 2012 IEEE.


Niu Z.,Xidian University | Hua G.,Stevens Institute of Technology | Gao X.,Xidian University | Tian Q.,University of Texas at San Antonio
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2014

In this paper, we address the problem of recognizing images with weakly annotated text tags. Most previous work either cannot be applied to the scenarios where the tags are loosely related to the images, or simply take a pre-fusion at the feature level or a post-fusion at the decision level to combine the visual and textual content. Instead, we first encode the text tags as the relations among the images, and then propose a semi-supervised relational topic model (ss-RTM) to explicitly model the image content and their relations. In such way, we can efficiently leverage the loosely related tags, and build an intermediate level representation for a collection of weakly annotated images. The intermediate level representation can be regarded as a mid-level fusion of the visual and textual content, which is able to explicitly model their intrinsic relationships. Moreover, image category labels are also modeled in the ss-RTM, and recognition can be conducted without training an additional discriminative classifier. Our extensive experiments on social multimedia datasets (images+tags) demonstrated the advantages of the proposed model. © 2014 IEEE.


Liu X.,Beihang University | He J.,Facebook | Deng C.,Xidian University | Lang B.,Beihang University
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2014

Hashing technique has become a promising approach for fast similarity search. Most of existing hashing research pursue the binary codes for the same type of entities by preserving their similarities. In practice, there are many scenarios involving nearest neighbor search on the data given in matrix form, where two different types of, yet naturally associated entities respectively correspond to its two dimensions or views. To fully explore the duality between the two views, we propose a collaborative hashing scheme for the data in matrix form to enable fast search in various applications such as image search using bag of words and recommendation using user-item ratings. By simultaneously preserving both the entity similarities in each view and the interrelationship between views, our collaborative hashing effectively learns the compact binary codes and the explicit hash functions for out-of-sample extension in an alternating optimization way. Extensive evaluations are conducted on three well-known datasets for search inside a single view and search across different views, demonstrating that our proposed method outperforms state-of-the-art baselines, with significant accuracy gains ranging from 7.67% to 45.87% relatively. © 2014 IEEE.


Zhao F.,Communication University of China | Jiao L.,Xidian University | Liu H.,Shaanxi Normal University
Digital Signal Processing: A Review Journal | Year: 2013

The generalized fuzzy c-means clustering algorithm with improved fuzzy partition (GFCM) is a novel modified version of the fuzzy c-means clustering algorithm (FCM). GFCM under appropriate parameters can converge more rapidly than FCM. However, it is found that GFCM is sensitive to noise in gray images. In order to overcome GFCM's sensitivity to noise in the image, a kernel version of GFCM with spatial information is proposed. In this method, first a term about the spatial constraints derived from the image is introduced into the objective function of GFCM, and then the kernel induced distance is adopted to substitute the Euclidean distance in the new objective function. Experimental results show that the proposed method behaves well in segmentation performance and convergence speed for gray images corrupted by noise. © 2012 Elsevier Inc. All rights reserved.


Bian H.,Xinjiang Normal University | Yu H.,Xidian University
NSWCTC 2010 - The 2nd International Conference on Networks Security, Wireless Communications and Trusted Computing | Year: 2010

Delay/Disruption Tolerant Networks (DTN) often use multi-copy routing protocols to improve the efficiency that the messages are delivered successfully, but the network load is increased by vast message copies. A new scheme is presented using threshold method on multi-copy routing protocol. The all nodes are added an encounter counter in the message transferred. If the counter reaches the set threshold of counter, the node removes the message copy. With the proper threshold, the message copies decrease obviously and are removed completely in the end, at the same time the successful delivery efficiency is still the same as the Epidemic Routing. In some environments we can abandon TTL or anti-packet approach about redundancy removing of message copies. In simulation, we compare variation trend of the message copies among vary threshold in two scenes. © 2010 IEEE.


Jiang J.-Z.,Xidian University | Jiang J.-Z.,Guilin University of Electronic Technology | Shui P.-L.,Xidian University
Signal Processing | Year: 2012

In this paper, the structure of the 2D oversampled DFT modulated filter banks is analyzed and a spatial-domain condition of a filter bank without transfer function distortion is derived. Based upon the spatial-domain condition, a modified Newtons method is presented for fast design of 2D oversampled linear phase (LP) DFT modulated filter banks with nearly perfect reconstruction (NPR). We formulate the design problem into an unconstrained optimization with a fourth-order objective function, which is the weighted sum of the transfer function distortion of the filter bank and the stopband energy of the prototype filter (PF). The optimization is solved by the modified Newtons method, where each of iterations updates the PF by a set of linear equations. It is proved that the iteration process fast converges to a stationary point of the objective function. Compared with the existing methods, the new method is fast in computation and can design 2D filter banks with a large number of subbands. © 2011 Elsevier B.V.


Wang P.,Xidian University | Zhang L.,Xidian University | Guo L.,Xidian University | Huang F.,Sun Yat Sen University | And 3 more authors.
Optics Express | Year: 2014

The average bit error rate (BER) for binary phase-shift keying (BPSK) modulation in free-space optical (FSO) links over turbulence atmosphere modeled by the exponentiated Weibull (EW) distribution is investigated in detail. The effects of aperture averaging on the average BERs for BPSK modulation under weak-to-strong turbulence conditions are studied. The average BERs of EW distribution are compared with Lognormal (LN) and Gamma-Gamma (GG) distributions in weak and strong turbulence atmosphere, respectively. The outage probability is also obtained for different turbulence strengths and receiver aperture sizes. The analytical results deduced by the generalized Gauss-Laguerre quadrature rule are verified by the Monte Carlo simulation. This work is helpful for the design of receivers for FSO communication systems. © 2014 Optical Society of America.


Wang X.,Xidian University | Bai B.,Xidian University | Ma X.,Sun Yat Sen University
IEEE International Symposium on Information Theory - Proceedings | Year: 2010

In this paper, we present a low-complexity joint detection-decoding algorithm for nonbinary LDPC codedmodulation systems. The algorithm combines hard-decision decoding using the message-passing strategy with the signal detector in an iterative manner. It requires low computational complexity, offers good system performance and has a fast rate of decoding convergence. Compared to the q-ary sum-product algorithm (QSPA), it provides an attractive candidate for practical applications of q-ary LDPC codes. © 2010 IEEE.


Sun J.,University of Tennessee at Knoxville | Zhu X.,Xidian University | Zhang C.,University of Florida | Fang Y.,University of Florida
IEEE Journal on Selected Areas in Communications | Year: 2011

Natural disasters and terrorism threaten our nation's safety and security, rendering post-disaster rescue mission critical. It is of paramount importance to carry out rescue work relying on secure and dependable networking. In this paper, we propose RescueMe, location-based vehicular ad hoc networks (VANETs), to aid in secure and dependable rescue planning for the efficient allocation of rescue resources. RescueMe leverages the location information stored during normal network operations to facilitate post-disaster rescue planning, while guaranteeing that the sensitive user location information is not exploited to trace a user's whereabouts when disasters are absent, even if the most powerful collusion attack is allowed. We provide a novel construction for the location update message, and propose several enhancements, to achieve the functional and security goals of RescueMe.


Deng C.,Xidian University | Ji R.,Xiamen University | Liu W.,IBM | Tao D.,University of Technology, Sydney | Gao X.,Xidian University
Proceedings of the IEEE International Conference on Computer Vision | Year: 2013

Visual reranking has been widely deployed to refine the quality of conventional content-based image retrieval engines. The current trend lies in employing a crowd of retrieved results stemming from multiple feature modalities to boost the overall performance of visual reranking. However, a major challenge pertaining to current reranking methods is how to take full advantage of the complementary property of distinct feature modalities. Given a query image and one feature modality, a regular visual reranking framework treats the top-ranked images as pseudo positive instances which are inevitably noisy, difficult to reveal this complementary property, and thus lead to inferior ranking performance. This paper proposes a novel image reranking approach by introducing a Co-Regularized Multi-Graph Learning (Co-RMGL) framework, in which the intra-graph and inter-graph constraints are simultaneously imposed to encode affinities in a single graph and consistency across different graphs. Moreover, weakly supervised learning driven by image attributes is performed to denoise the pseudo-labeled instances, thereby highlighting the unique strength of individual feature modality. Meanwhile, such learning can yield a few anchors in graphs that vitally enable the alignment and fusion of multiple graphs. As a result, an edge weight matrix learned from the fused graph automatically gives the ordering to the initially retrieved results. We evaluate our approach on four benchmark image retrieval datasets, demonstrating a significant performance gain over the state-of-the-arts. © 2013 IEEE.


Su Y.,Tsinghua University | Fu Y.,State University of New York at Buffalo | Gao X.,Xidian University | Tian Q.,University of Texas at San Antonio
IEEE Transactions on Image Processing | Year: 2012

Canonical correlation has been prevalent for multiset-based pairwise subspace analysis. As an extension, discriminant canonical correlations (DCCs) have been developed for classification purpose by learning a global subspace based on Fisher discriminant modeling of pairwise subspaces. However, the discriminative power of DCCs is not optimal as it only measures the local canonical correlations within subspace pairs, which lacks the global measurement among all the subspaces. In this paper, we propose a multiset discriminant canonical correlation method, i.e., multiple principal angle (MPA). It jointly considers both local and global canonical correlations by iteratively learning multiple subspaces (one for each set) as well as a global discriminative subspace, on which the angle among multiple subspaces of the same class is minimized while that of different classes is maximized. The proposed computational solution is guaranteed to be convergent with much faster converging speed than DCC. Extensive experiments on pattern recognition applications demonstrate the superior performance of MPA compared to existing subspace learning methods. © 2011 IEEE.


Bai B.,Xidian University | Ma X.,Sun Yat Sen University
Science China Information Sciences | Year: 2012

This paper introduces a new class of rateless forward error correction (FEC) codes, which are called semi-random Kite (SR-Kite) codes. By introducing fixed patterns to an original purely random sparse parity-check matrix, the proposed code can lower down the error floors. We present a simulation-based greedy optimization algorithm to design the degree distribution of SR-Kite codes for independent Rayleigh fading channels. The performances of SR-Kite codes under maximum likelihood decoding are analyzed for both AWGN and independent Rayleigh fading channels via union bound. Both the analysis and simulation results show that the proposed codes perform well over AWGN and fading channels within a wide range of signal-to-noise-ratios. Moreover, we combine SR-Kite codes with high-order modulation schemes to obtain a continuously variable spectral efficiency in a large range of SNRs. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.


Liu J.,Xidian University | Kato N.,Tohoku University
IEEE Transactions on Wireless Communications | Year: 2016

There has been surging research interest in utilizing mobile phones for information relaying in postdisaster areas lacking infrastructure support. A common complication for such postdisaster ad hoc communication is how to efficiently control the forwarding behaviors of relay nodes so as to save their energy consumption and buffer usage while simultaneously guaranteeing the desired delivery performance. Different from previous studies, we consider in this paper an explicit probabilistic stopping mechanism, where a relay node that is actively disseminating a message will stop spreading the message with a certain probability, after meeting another node having already received the message. Besides developing a two-dimensional Markov chain framework to characterize the message propagation process, we also derive the average time required for completion of message propagation, the probability distribution, the expectation, the variance of the fraction of nodes finally receiving the message, etc. Our results reveal that the explicit probabilistic stopping mechanism is very desirable for postdisaster communication, even being able to guarantee a majority of nodes in final message reception. What is more, the developed framework provides us a deeper understanding on how network parameters may affect these important performance metrics, which further enables network designers to accordingly tune controllable parameters. © 2002-2012 IEEE.


Zhang Z.,Xidian University | Han Z.,University of Houston | Li H.,Kyung Hee University | Yang D.,University of Tennessee at Knoxville | Pei C.,Xidian University
IEEE Transactions on Wireless Communications | Year: 2011

Wideband spectrum sensing in heterogenous cognitive radio networks has two significant challenges to tackle. One is the spectrum acquisition in the wideband scenario due to the limited sampling capability; the other is how to collaborate among the secondary users. Compressed spectrum sensing provides a powerful approach to acquire wideband signal. Moreover, most cooperative spectrum sensing methods assume that all the secondary users experience the same occupancy of primary users, which may be infeasible in a heterogenous spectrum environment where secondary users at different locations may be affected by different primary users. In this paper, we propose a probabilistic graphical model to represent and fuse multi-prior information from one hop neighboring secondary users. Belief propagation (BP) is used for the statistical inference of the spectrum occupancy. Numerical simulation results demonstrate that the proposed BP based cooperative compressed spectrum sensing can effectively achieve cooperation in heterogenous environments and improve performance of compressed spectrum sensing under a low sampling rate and low signal-to-noise ratio (SNR), compared with the other distributed cooperative compressed sensing methods. © 2006 IEEE.


Wang N.,Xidian University | Tao D.,University of Technology, Sydney | Gao X.,Xidian University | Li X.,Chinese Academy of Sciences | Li J.,Xidian University
International Journal of Computer Vision | Year: 2014

This paper comprehensively surveys the development of face hallucination (FH), including both face super-resolution and face sketch-photo synthesis techniques. Indeed, these two techniques share the same objective of inferring a target face image (e.g. high-resolution face image, face sketch and face photo) from a corresponding source input (e.g. low-resolution face image, face photo and face sketch). Considering the critical role of image interpretation in modern intelligent systems for authentication, surveillance, law enforcement, security control, and entertainment, FH has attracted growing attention in recent years. Existing FH methods can be grouped into four categories: Bayesian inference approaches, subspace learning approaches, a combination of Bayesian inference and subspace learning approaches, and sparse representation-based approaches. In spite of achieving a certain level of development, FH is limited in its success by complex application conditions such as variant illuminations, poses, or views. This paper provides a holistic understanding and deep insight into FH, and presents a comparative analysis of representative methods and promising future directions. © 2013 Springer Science+Business Media New York.


Lei C.-X.,Shandong University of Technology | Wu Z.-S.,Xidian University
Wuli Xuebao/Acta Physica Sinica | Year: 2010

Based on fractal theory, the Monte Carlo method is used to simulate the structures of fractal soot aggregates in random distribution. The radiative properties of randomly distributed soot aggregates are studied using the discrete dipole approximation (DDA), and the effects of the fractal dimension, the monomer diameters, the number of monomers in the soot aggregates and the refractive index on the radiative properties of aggregated soot particles are analyzed. The results show that the radiative properties of randomly distributed soot aggregates of a given fractal dimension are complex functions of the monomer diameters, the number of monomers in the aggregates, and the refractive index. For small values of the monomer diameters, the absorption cross section of soot aggregates tends to be relatively constant when the fractal dimension is small, but increases rapidly when the fractal dimension exceeds two. However, a monotonical reduction in light absorption with the increase of the fractal dimension is observed for soot aggregates with sufficiently large monomer diameters, number of monomers, and refractive index. The scattering cross section, extinction cross section and single-scattering albedo increase monotonically with the increase of the fractal dimension. In a word, the results for soot aggregates differ profoundly from those calculated for the equivalent spherical particles, and the discrepancies between them change litte with the increase of the fractal dimension. This research is of scientific value in studying the radiative properties of aerosols and their climatic effects. © 2010 Chin. Phys. Soc.


Su Y.,Tsinghua University | Gao X.,Xidian University | Li X.,Chinese Academy of Sciences | Tao D.,Intelligent Systems Technology, Inc.
IEEE Transactions on Systems, Man, and Cybernetics, Part B: Cybernetics | Year: 2012

Conventional regression methods, such as multivariate linear regression (MLR) and its extension principal component regression (PCR), deal well with the situations that the data are of the form of low-dimensional vector. When the dimension grows higher, it leads to the under sample problem (USP): the dimensionality of the feature space is much higher than the number of training samples. However, little attention has been paid to such a problem. This paper first adopts an in-depth investigation to the USP in PCR, which answers three questions: 1) Why is USP produced? 2) What is the condition for USP, and 3) How is the influence of USP on regression. With the help of the above analysis, the principal components selection problem of PCR is presented. Subsequently, to address the problem of PCR, a multivariate multilinear regression (MMR) model is proposed which gives a substitutive solution to MLR, under the condition of multilinear objects. The basic idea of MMR is to transfer the multilinear structure of objects into the regression coefficients as a constraint. As a result, the regression problem is reduced to find two low-dimensional coefficients so that the principal components selection problem is avoided. Moreover, the sample size needed for solving MMR is greatly reduced so that USP is alleviated. As there is no closed-form solution for MMR, an alternative projection procedure is designed to obtain the regression matrices. For the sake of completeness, the analysis of computational cost and the proof of convergence are studied subsequently. Furthermore, MMR is applied to model the fitting procedure in the active appearance model (AAM). Experiments are conducted on both the carefully designed synthesizing data set and AAM fitting databases verified the theoretical analysis. © 1996-2012 IEEE.


Zhu X.,Queensland University of Technology | Huang Z.,Queensland University of Technology | Cui J.,Xidian University | Shen H.T.,Queensland University of Technology
IEEE Transactions on Multimedia | Year: 2013

Traditional approaches to video tagging are designed to propagate tags at the same level, such as assigning the tags of training videos (or shots) to the test videos (or shots), such as generating tags for the test video when the training videos are associated with the tags at the video-level or assigning tags to the test shot when given a collection of annotated shots. This paper focuses on automatical shot tagging given a collection of videos with the tags at the video-level. In other words, we aim to assign specific tags from the training videos to the test shot. The paper solves the V2S issue by assigning the test shot with the tags deriving from parts of the tags in a part of training videos. To achieve the goal, the paper first proposes a novel Graph Sparse Group Lasso (shorted for GSGL) model to linearly reconstruct the visual feature of the test shot with the visual features of the training videos, i.e., finding the correlation between the test shot and the training videos. The paper then proposes a new tagging propagation rule to assign the video-level tags to the test shot by the learnt correlations. Moreover, to effectively build the reconstruction model, the proposed GSGL simultaneously takes several constraints into account, such as the inter-group sparsity, the intra-group sparsity, the temporal-spatial prior knowledge in the training videos and the local structure of the test shot. Extensive experiments on public video datasets are conducted, which clearly demonstrate the effectiveness of the proposed method for dealing with the video-to-shot tag propagation. © 2012 IEEE.


Gao S.,Xidian University | Li Y.-S.,Xidian University | Zhang M.-S.,Sun Yat Sen University
IEEE Transactions on Microwave Theory and Techniques | Year: 2010

In this paper, an efficient algebraic method for the passivity enforcement of macromodels is presented. The method is based on quadratic programming with equality constraint. The differences between equality constraint and conventional inequality constraint are discussed. Compared with the general quadratic programming-based method, where the passivity violations are compensated via numerical optimization, the presented method is based on the solution of sparse linear equations. With the special sparse structure of macromodels, the passivity compensation is equivalent to the solution of some small size linear equations. This gives large savings for CPU time and memory requirement. Several examples show that the presented method yields accurate passive macromodels in a limited simulation time. © 2010 IEEE.


Wang S.,Zhejiang GongShang University | Wang C.,Zhejiang GongShang University | Zhou M.,Tongji University | Zhou M.,New Jersey Institute of Technology | And 2 more authors.
IEEE Transactions on Systems, Man, and Cybernetics: Systems | Year: 2012

Strict minimal siphons (SMS) play an important role in the development of deadlock control policies for flexible manufacturing systems (FMS). For a class of Petri nets called Systems of Simple Sequential Processes with Resources (S3PR), the resource circuit-based method is an effective way to compute SMS. In this paper, a more effective one to compute SMS is proposed. First, the concepts of loop resource subsets and their characteristic resource subnets are proposed. Next, sufficient and necessary conditions for loop resource subsets to generate SMS are established. Finally, an algorithm is given to find all the SMS based on loop resource subsets. Since the number of loop resource subsets is much less than that of resource circuits and their combinations, the computational efficiency of the SMS enumeration task is significantly improved by the proposed method. An FMS example is used to illustrate the application of the proposed method, and computational time comparisons are provided on several S3PR s to show its superior efficiency. © 2006 IEEE.


An L.,Xidian University | Gao X.,Xidian University | Li X.,Xidian University | Tao D.,Xidian University | And 2 more authors.
IEEE Transactions on Image Processing | Year: 2012

Robust reversible watermarking (RRW) methods are popular in multimedia for protecting copyright, while preserving intactness of host images and providing robustness against unintentional attacks. However, conventional RRW methods are not readily applicable in practice. That is mainly because: 1) they fail to offer satisfactory reversibility on large-scale image datasets; 2) they have limited robustness in extracting watermarks from the watermarked images destroyed by different unintentional attacks; and 3) some of them suffer from extremely poor invisibility for watermarked images. Therefore, it is necessary to have a framework to address these three problems, and further improve its performance. This paper presents a novel pragmatic framework, wavelet-domain statistical quantity histogram shifting and clustering (WSQH-SC). Compared with conventional methods, WSQH-SC ingeniously constructs new watermark embedding and extraction procedures by histogram shifting and clustering, which are important for improving robustness and reducing run-time complexity. Additionally, WSQH-SC includes the property-inspired pixel adjustment to effectively handle overflow and underflow of pixels. This results in satisfactory reversibility and invisibility. Furthermore, to increase its practical applicability, WSQH-SC designs an enhanced pixel-wise masking to balance robustness and invisibility. We perform extensive experiments over natural, medical, and synthetic aperture radar images to show the effectiveness of WSQH-SC by comparing with the histogram rotation-based and histogram distribution constrained methods. © 1992-2012 IEEE.


Zhang X.,Xidian University | Yang Y.,Xidian University | Jiao L.C.,Xidian University | Dong F.,University of Bedfordshire
Pattern Recognition | Year: 2013

Due to its various applications, human action recognition has been widely studied and achieved tremendous progress. However, how to learn an accurate and discriminative behavior representation based on the extracted features remains as a challenging problem. In this paper, we present an effective coding scheme that can discover the manifold structure of the learned features with an l 2-norm regularization. Coupled with a local constraint, the proposed coding scheme, which has an analytical solution can learn an accurate, compact and yet discriminative behavior representation. After the behavior representations are obtained, the action recognition problem is formulated as a sparse linear representation of an overcomplete dictionary constructed by labeled behavior representations. The same manifold l2-norm regularization is also employed in this stage. The reconstruction error associated with each class is used for classification. Experimental results demonstrate the effectiveness of the proposed approach on several public datasets including various physical actions and facial expressions. © 2012 Elsevier Ltd. All rights reserved.


Xiao J.-K.,Xidian University | Zhu W.-J.,Hohai University
Progress in Electromagnetics Research Symposium | Year: 2011

Defected microstrip structure (DMS) has similar properties with defected ground structure (DGS) but without any leakage through the ground plane. In this report, the stop-band performance of DMS is studied, and new single band, dual-band and tri-band bandstop filters with DMS are proposed. The dual-band and tri-band bandstop filters are fabricated, and the measured results are similar to the simulation. The new DMS bandstop filters have advantages of good frequency selectivity, low loss and simple circuit topology, and simultaneously, has a miniature circuit size of no more than 30mm × 1.2 mm.


Zhang K.,Xidian University | Gao X.,Xidian University | Tao D.,University of Technology, Sydney | Li X.,CAS Xi'an Institute of Optics and Precision Mechanic
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2012

Reconstruction- and example-based super-resolution (SR) methods are promising for restoring a high-resolution (HR) image from low-resolution (LR) image(s). Under large magnification, reconstruction-based methods usually fail to hallucinate visual details while example-based methods sometimes introduce unexpected details. Given a generic LR image, to reconstruct a photo-realistic SR image and to suppress artifacts in the reconstructed SR image, we introduce a multi-scale dictionary to a novel SR method that simultaneously integrates local and non-local priors. The local prior suppresses artifacts by using steering kernel regression to predict the target pixel from a small local area. The non-local prior enriches visual details by taking a weighted average of a large neighborhood as an estimate of the target pixel. Essentially, these two priors are complementary to each other. Experimental results demonstrate that the proposed method can produce high quality SR recovery both quantitatively and perceptually. © 2012 IEEE.


Ye J.,Xidian University | Jin H.,Xi'an Shiyou University | Zhang Q.,Xidian University
Digital Signal Processing: A Review Journal | Year: 2013

Blind source separation (BSS) consists of recovering the statistically independent source signals from their linear mixtures without knowing the mixing coefficients. Pre-whitening is a useful pre-processing technique in BSS. However, BSS algorithms based on the pre-whitened data lack the equivariance property, one of the significant properties in BSS. By transforming the pre-whitening into a weighted orthogonal constraint condition, this paper proposes a new definition of the contrast function. In light of the constrained optimization method, various weighted orthogonal constrained BSS algorithms with equivariance property are developed. Simulations on man-made signals and practical speech signals show the proposed weighted orthogonal constrained BSS algorithms have better separation ability, convergent speed and steady state performance. © 2012 Elsevier Inc.


Xiong P.,Tsinghua University | Xiong P.,Georgia Institute of Technology | Fan Y.,Tsinghua University | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2010

Business Process Execution Language for Web Services (BPEL) is becoming the industrial standard for modeling Web-service-based business processes. Behavioral compatibility for Web service composition is one of the most important topics. The commonly used reachability exploration method focuses on verifying deadlock freeness. When this property is violated, the states and traces in the reachability graph only give clues to redesign the composition. The redesign must then repeat itself until no deadlock is found. In this paper, multiple Web service interaction is modeled with a Petri net called Composition net (C-net for short). The problem of behavioral compatibility among Web services is hence transformed into the deadlock structure problem of a C-net. If services are incompatible, a policy based on appending additional information channels is proposed. It is proved that the policy can offer a good solution that can be mapped back into the BPEL models automatically. © 2009 IEEE.


Li X.,Xidian University | Li Z.,Xidian University | Li Z.,Guilin University of Electronic Technology
Measurement Science and Technology | Year: 2012

This paper presents a novel calibration method for tri-axial field sensors, such as magnetometers and accelerometers, in strap-down navigation systems. Strap-down tri-axial sensors have been widely used as they have the advantages of small size and low cost, but they need to be calibrated in order to ensure their accuracy. The most commonly used calibration method for a tri-axial field sensor is based on ellipsoid fitting, which has no requirement for external references. However, the self-calibration based on ellipsoid fitting is unable to determine and compensate the mutual misalignment between different sensors in a multi-sensor system. Therefore, a novel calibration method that employs the invariance of the dot product of two constant vectors is introduced in this paper. The proposed method, which is named dot product invariance method, brings a complete solution for the error model of tri-axial field sensors, and can solve the problem of alignment in a multi-sensor system. Its effectiveness and superiority over the ellipsoid fitting method are illustrated by numerical simulations, and its application on a digital magnetic compass shows significant enhancement of the heading accuracy. © 2012 IOP Publishing Ltd.


Chen F.,University of Florida | Zhai H.,University of Florida | Zhai H.,Philips | Fang Y.,Xidian University
IEEE Journal on Selected Areas in Communications | Year: 2010

The task of estimating path available bandwidth is difficult but paramount for QoS routing in supporting bandwidth-demanding traffic in multirate and multihop wireless ad hoc networks. The multirate capability and the impact of background traffic has not been carefully studied for the problem of estimating path available bandwidth in prior works. In this paper, we develop a theoretical model for estimating the available bandwidth of a path by considering interference from both background traffic and traffic along the path. We show that the clique constraint widely used to construct upper bounds does not hold any more when links are allowed to use different rates at different time. In our proposed model, traditional clique is coupled with rate vector to more properly characterize the conflicting relationships among links in wireless ad hoc networks where time-varying link adaption is used. Based on this model, we also investigate the problem of joint optimization of QoS routing and link scheduling. Several routing metrics and a heuristic algorithm are proposed. The newly proposed conservative clique constraint performs the best among the studied metrics in estimating available bandwidth of flows with background traffic. © 2010 IEEE.


Zhang C.,University of Florida | Sun J.,University of Florida | Zhu X.,Xidian University | Fang Y.,University of Florida
IEEE Network | Year: 2010

Online social networks such as Facebook, Myspace, and Twitter have experienced exponential growth in recent years. These OSNs offer attractive means of online social interactions and communications, but also raise privacy and security concerns. In this article we discuss the design issues for the security and privacy of OSNs. We find there are inherent design conflicts between these and the traditional design goals of OSNs such as usability and sociability. We present the unique security and privacy design challenges brought by the core functionalities of OSNs and highlight some opportunities of utilizing social network theory to mitigate these design conflicts. © 2010 IEEE.


Wang H.,Xidian University | Yao X.,University of Birmingham
IEEE Transactions on Cybernetics | Year: 2014

Nondominated sorting plays an important role in Pareto-based multiobjective evolutionary algorithms (MOEAs). When faced with many-objective optimization problems multiobjective optimization problems (MOPs) with more than three objectives, the number of comparisons needed in nondominated sorting becomes very large. In view of this, a new corner sort is proposed in this paper. Corner sort first adopts a fast and simple method to obtain a nondominated solution from the corner solutions, and then uses the nondominated solution to ignore the solutions dominated by it to save comparisons. Obtaining the nondominated solutions requires much fewer objective comparisons in corner sort. In order to evaluate its performance, several state-of-the-art nondominated sorts are compared with our corner sort on three kinds of artificial solution sets of MOPs and the solution sets generated from MOEAs on benchmark problems. On one hand, the experiments on artificial solution sets show the performance on the solution sets with different distributions. On the other hand, the experiments on the solution sets generated from MOEAs show the influence that different sorts bring to MOEAs. The results show that corner sort performs well, especially on many-objective optimization problems. Corner sort uses fewer comparisons than others. © 2013 IEEE.


Li Y.,Xidian University | Jiao L.,Xidian University | Shang R.,Xidian University | Stolkin R.,University of Birmingham
Information Sciences | Year: 2015

This paper proposes a dynamic-context cooperative quantum-behaved particle swarm optimization algorithm. The proposed algorithm incorporates a new method for dynamically updating the context vector each time it completes a cooperation operation with other particles. We first explain how this leads to enhanced search ability and improved optimization over previous methods, and demonstrate this empirically with comparative experiments using benchmark test functions. We then demonstrate a practical application of the proposed method, by showing how it can be applied to optimize the parameters for Otsu image segmentation for processing medical images. Comparative experimental results show that the proposed method outperforms other state-of-the-art methods from the literature. © 2014 Elsevier Inc. All rights reserved.


Song Y.,University of Florida | Zhang C.,University of Florida | Fang Y.,Xidian University
IEEE Transactions on Mobile Computing | Year: 2010

In this work, the stochastic traffic engineering problem in multihop cognitive wireless mesh networks is addressed. The challenges induced by the random behaviors of the primary users are investigated in a stochastic network utility maximization framework. For the convex stochastic traffic engineering problem, we propose a fully distributed algorithmic solution which provably converges to the global optimum with probability one. We next extend our framework to the cognitive wireless mesh networks with nonconvex utility functions, where a decentralized algorithmic solution, based on learning automata techniques, is proposed. We show that the decentralized solution converges to the global optimum solution asymptotically. © 2010 IEEE.


Li P.,Mississippi State University | Zhang C.,University of Florida | Fang Y.,University of Florida | Fang Y.,Xidian University
IEEE Transactions on Mobile Computing | Year: 2011

Considering a disk of unit area with n nodes, we investigate the capacity of wireless networks using directional antennas. First, we study the throughput capacity of random directional networks with multihop relay schemes, and find that the capacity gain compared to random omnidirectional networks is O(\log n), which is tighter than previous results. We also show that using directional antennas can significantly reduce power consumption in the networks. Second, for the first time, we explore the throughput capacity of random directional networks with one-hop relay schemes. Interestingly and against our intuition, we find that one-hop instead of multihop delivery schemes can make random directional networks scale. Third, we investigate the trade-offs between transmission range and throughput in random directional networks and show that using larger transmission range can result in higher throughput. Finally, we present a lower bound on the transport capacity of arbitrary directional networks, and find that without side lobe directional antenna gain, arbitrary directional networks can also scale. © 2011 IEEE.


Cheng M.,Xidian University | Guo L.,Xidian University | Zhang Y.,Jiangnan University
Optics Express | Year: 2015

Analytic expression of the receiver-aperture-averaged scintillation index (SI) was derived for Gaussian-beam waves propagating through non-Kolmogorov maritime atmospheric environment by establishing a generalized maritime atmospheric spectrum model. The error performance of an intensity-modulated and direct-detection (IM/DD) free-space optical (FSO) system was investigated using the derived SI and lognormal distribution. The combined effects of non-Kolmogorov power-law exponent, turbulence inner scale, structure parameter, propagation distance, receiver aperture, and wavelength were also evaluated. Results show that inner scale and power-law exponent obviously affect SI. Large wavelength and receiver aperture can mitigate the effects of turbulence. The proposed model can be evaluated ship-to-ship/shore FSO system performance. © 2015 Optical Society of America.


Cai S.,Hong Kong Polytechnic University | Zhang L.,Hong Kong Polytechnic University | Zuo W.,Harbin Institute of Technology | Feng X.,Xidian University
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2016

Conventional representation based classifiers, ranging from the classical nearest neighbor classifier and nearest subspace classifier to the recently developed sparse representation based classifier (SRC) and collaborative representation based classifier (CRC), are essentially distance based classifiers. Though SRC and CRC have shown interesting classification results, their intrinsic classification mechanism remains unclear. In this paper we propose a probabilistic collaborative representation framework, where the probability that a test sample belongs to the collaborative subspace of all classes can be well defined and computed. Consequently, we present a probabilistic collaborative representation based classifier (ProCRC), which jointly maximizes the likelihood that a test sample belongs to each of the multiple classes. The final classification is performed by checking which class has the maximum likelihood. The proposed ProCRC has a clear probabilistic interpretation, and it shows superior performance to many popular classifiers, including SRC, CRC and SVM. Coupled with the CNN features, it also leads to state-of-the-art classification results on a variety of challenging visual datasets.


Zuo W.,Harbin Institute of Technology | Zuo W.,Hong Kong Polytechnic University | Meng D.,Xi'an Jiaotong University | Zhang L.,Hong Kong Polytechnic University | And 2 more authors.
Proceedings of the IEEE International Conference on Computer Vision | Year: 2013

In many sparse coding based image restoration and image classification problems, using non-convex ℓp-norm minimization (0 ≤p <1) can often obtain better results than the convex ℓ1-norm minimization. A number of algorithms, e.g., iteratively reweighted least squares (IRLS), iteratively thresholding method (ITM-ℓp), and look-up table (LUT), have been proposed for non-convex ℓp-norm sparse coding, while some analytic solutions have been suggested for some specific values of p. In this paper, by extending the popular soft-thresholding operator, we propose a generalized iterated shrinkage algorithm (GISA) for ℓp-norm non-convex sparse coding. Unlike the analytic solutions, the proposed GISA algorithm is easy to implement, and can be adopted for solving non-convex sparse coding problems with arbitrary p values. Compared with LUT, GISA is more general and does not need to compute and store the look-up tables. Compared with IRLS and ITM-ℓp, GISA is theoretically more solid and can achieve more accurate solutions. Experiments on image restoration and sparse coding based face recognition are conducted to validate the performance of GISA. © 2013 IEEE.


Cui Z.,Xidian University | Han Y.,Xidian University | Zhang H.,Anhui Science and Technology University
Journal of the Optical Society of America B: Optical Physics | Year: 2011

The surface integral equation method is introduced to characterize the scattering of an arbitrarily incident focused Gaussian beam by arbitrarily shaped homogeneous dielectric particles. The incident Gaussian beam is represented by the Davis first-order approximation in Cartesian coordinates. For a numerical solution, the particles with arbitrary shapes are modeled by using surface triangular patches and the surface integral equations are discretized with the method of moments. The resulting matrix equations are solved by means of the parallel conjugate gradient method. The calculated results for a sphere and a spheroid are compared with those from the generalized Lorenz- Mie theory, and very good agreements are observed. We also present the numerical results for several selected irregular particles. These results can be used as a reference for other numerical methods to analyze the light scattering by irregular particles illuminated by Gaussian beam. © 2011 Optical Society of America.


Li P.,Mississippi State University | Fang Y.,University of Florida | Fang Y.,Xidian University
Proceedings - IEEE INFOCOM | Year: 2010

Although capacity has been extensively studied in wireless networks, most of the results are for homogeneous wireless networks where all nodes are assumed identical. In this paper, we investigate the capacity of heterogeneous wireless networks with general network settings. Specifically, we consider a dense network with n normal nodes and m = nb (0 < b < 1) more powerful helping nodes in a rectangular area with width b(n) and length 1/b(n), where b(n) = nw and -1/2 < w ≤ 0. We assume there are n flows in the network. All the n normal nodes are sources while only randomly chosen nd (0 < d < 1) normal nodes are destinations. We further assume the n normal nodes are uniformly and independently distributed, while the m helping nodes are either regularly placed or uniformly and independently distributed, resulting in two different kinds of networks called Regular Heterogeneous Wireless Networks and Random Heterogeneous Wireless Networks, respectively. In this paper, we attempt to find out what a heterogeneous wireless network with general network settings can do by deriving a lower bound on the capacity. We also explore the conditions under which heterogeneous wireless networks can provide throughput higher than traditional homogeneous wireless networks. ©2010 IEEE.


Li P.,Mississippi State University | Fang Y.,University of Florida | Fang Y.,Xidian University | Li J.,University of Tsukuba
Proceedings - IEEE INFOCOM | Year: 2010

Throughput capacity in wireless ad hoc networks has been studied extensively under many different mobility models such as i.i.d. mobility model, Brownian mobility model, random walk model, and so on. Most of these research works assume global mobility, i.e., each node moves around in the whole network, and the results show that a constant per-node throughput can be achieved at the cost of very high expected average end-to-end delay. Thus, we are having a very big gap here, either low throughput and low delay in static networks or high throughput and high delay in mobile networks. In this paper, employing a more practical restricted random mobility model, we try to fill in this gap. Specifically, we assume a network of unit area with n nodes is evenly divided into n2α cells with an area of n-2α where 0 ≤ α ≤ 1/2, each of which is further evenly divided into squares with an area of n-2α where 0 ≤ α ≤ β ≤ 1/2. All nodes can only move inside the cell which they are initially distributed in, and at the beginning of each time slot, every node moves from its current square to a uniformly chosen point in an uniformly chosen adjacent square. Proposing a new multi-hop relay scheme, we present an upper bound and a lower bound on per-node throughput capacity and expected average end-to-end delay, respectively. We finally explicitly show smooth trade-offs between throughput and delay by controlling nodes' mobility. ©2010 IEEE.


Ma Z.,Xidian University | Li Z.,Macau University of Science and Technology | Giua A.,Aix - Marseille University
IEEE Transactions on Automatic Control | Year: 2015

In this paper, a type of specifications called OR-AND Generalized Mutual Exclusion Constraints (GMEC) for place/transition nets is defined. Such a specification consists of a disjunction of conjunction of several single GMECs, i.e., the requirement is that, at any given time, the controlled system should satisfy at least one set of conjunctive GMECs. We show that a bounded OR-AND GMEC can be enforced by a special control structure composed by a set of AND-GMEC monitor places plus a switcher that determines the current active ones. We also show that such a simple control structure can be modified to ensure maximal permissiveness. This approach can be used in the framework of supervisory control in Petri nets. © 2015 IEEE.


Chen X.,Nanjing University of Aeronautics and Astronautics | Chen X.,Xidian University | Chen H.-H.,National Cheng Kung University | Meng W.,Harbin Institute of Technology
IEEE Communications Surveys and Tutorials | Year: 2014

Cognitive Radio has been recognized as a promising way to improve spectrum efficiency of wireless communications by exploiting under-utilized licensed spectrum in temporal, frequency, and spatial domains. As a remedy to the limited capability of a single node or network, cooperative communication technique has a potential to further improve the performance of cognitive networks, especially for spectrum sensing based cognitive networks. Given that spectrum efficiency of a cognitive network is determined jointly by spectrum sensing and access capabilities, it makes sense to employ cooperative techniques to enhance their performance. This article offers a tutorial on various cooperative techniques in cognitive networks, with its emphasis on spectrum sensing and access based cooperation, interference constraint based adaptive cooperative feedback, rateless network coding based cooperative transmission, and limited cooperation based interference coordination. Finally, numerical results are given to showcase advantages of the proposed cooperative schemes for cognitive networks. © 2014 IEEE.


Liu E.,Michigan State University | Liu E.,Xidian University | Jain A.K.,Michigan State University | Jain A.K.,Korea University | And 2 more authors.
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2013

With the availability of live-scan palmprint technology, high resolution palmprint recognition has started to receive significant attention in forensics and law enforcement. In forensic applications, latent palmprints provide critical evidence as it is estimated that about 30 percent of the latents recovered at crime scenes are those of palms. Most of the available high-resolution palmprint matching algorithms essentially follow the minutiae-based fingerprint matching strategy. Considering the large number of minutiae (about 1,000 minutiae in a full palmprint compared to about 100 minutiae in a rolled fingerprint) and large area of foreground region in full palmprints, novel strategies need to be developed for efficient and robust latent palmprint matching. In this paper, a coarse to fine matching strategy based on minutiae clustering and minutiae match propagation is designed specifically for palmprint matching. To deal with the large number of minutiae, a local feature-based minutiae clustering algorithm is designed to cluster minutiae into several groups such that minutiae belonging to the same group have similar local characteristics. The coarse matching is then performed within each cluster to establish initial minutiae correspondences between two palmprints. Starting with each initial correspondence, a minutiae match propagation algorithm searches for mated minutiae in the full palmprint. The proposed palmprint matching algorithm has been evaluated on a latent-to-full palmprint database consisting of 446 latents and 12,489 background full prints. The matching results show a rank-1 identification accuracy of 79.4 percent, which is significantly higher than the 60.8 percent identification accuracy of a state-of-the-art latent palmprint matching algorithm on the same latent database. The average computation time of our algorithm for a single latent-to-full match is about 141 ms for genuine match and 50 ms for impostor match, on a Windows XP desktop system with 2.2-GHz CPU and 1.00-GB RAM. The computation time of our algorithm is an order of magnitude faster than a previously published state-of-the-art-algorithm. © 1979-2012 IEEE.


Gu S.,Hong Kong Polytechnic University | Zhang L.,Hong Kong Polytechnic University | Zuo W.,Harbin Institute of Technology | Feng X.,Xidian University
Proceedings of the IEEE Computer Society Conference on Computer Vision and Pattern Recognition | Year: 2014

As a convex relaxation of the low rank matrix factorization problem, the nuclear norm minimization has been attracting significant research interest in recent years. The standard nuclear norm minimization regularizes each singular value equally to pursue the convexity of the objective function. However, this greatly restricts its capability and flexibility in dealing with many practical problems (e.g., denoising), where the singular values have clear physical meanings and should be treated differently. In this paper we study the weighted nuclear norm minimization (WNNM) problem, where the singular values are assigned different weights. The solutions of the WNNM problem are analyzed under different weighting conditions. We then apply the proposed WNNM algorithm to image denoising by exploiting the image nonlocal self-similarity. Experimental results clearly show that the proposed WNNM algorithm outperforms many state-of-the-art denoising algorithms such as BM3D in terms of both quantitative measure and visual perception quality. © 2014 IEEE.


Liu J.,Beijing Jiaotong University | Liu J.,University of Toronto | Li J.,Xidian University | Feng L.,CAS Institute of Automation | And 4 more authors.
Cortex | Year: 2014

Face pareidolia is the illusory perception of non-existent faces. The present study, for the first time, contrasted behavioral and neural responses of face pareidolia with those of letter pareidolia to explore face-specific behavioral and neural responses during illusory face processing. Participants were shown pure-noise images but were led to believe that 50% of them contained either faces or letters; they reported seeing faces or letters illusorily 34% and 38% of the time, respectively. The right fusiform face area (rFFA) showed a specific response when participants "saw" faces as opposed to letters in the pure-noise images. Behavioral responses during face pareidolia produced a classification image (CI) that resembled a face, whereas those during letter pareidolia produced a CI that was letter-like. Further, the extent to which such behavioral CIs resembled faces was directly related to the level of face-specific activations in the rFFA. This finding suggests that the rFFA plays a specific role not only in processing of real faces but also in illusory face perception, perhaps serving to facilitate the interaction between bottom-up information from the primary visual cortex and top-down signals from the prefrontal cortex (PFC). Whole brain analyses revealed a network specialized in face pareidolia, including both the frontal and occipitotemporal regions. Our findings suggest that human face processing has a strong top-down component whereby sensory input with even the slightest suggestion of a face can result in the interpretation of a face. © 2014 Elsevier Ltd.


Ma Y.,Xi'an University of Science and Technology | Li J.,Xidian University | Chen R.,Xidian University
IEEE Communications Letters | Year: 2012

For a three-cell constant cellular interfering network, a new property of alignment is identified, i.e., an interference alignment (IA) solution obtained in a user-cooperation scenario can also be applied to a non-cooperation environment. By using this property, an algorithm is proposed by jointly designing transmit and receive beamforming matrices. Analysis and simulation results show that more degrees of freedom (DoF) can be achieved compared with conventional schemes in most cases. © 2012 IEEE.


Huo C.,CAS Institute of Automation | Pan C.,CAS Institute of Automation | Huo L.,Xidian University | Zhou Z.,CAS Institute of Remote Sensing
IEEE Geoscience and Remote Sensing Letters | Year: 2012

A fast approach is proposed in this letter for large-size very high resolution image registration, which is accomplished based on coarse-to-fine strategy and blockwise scale-invariant feature transform (SIFT) matching. Coarse registration is implemented at low resolution level, which provides a geometric constraint. The constraint makes the blockwise SIFT matching possible and is helpful for getting more matched keypoints at the latter refined procedure. Refined registration is achieved by blockwise SIFT matching and global optimization on the whole matched keypoints based on iterative reweighted least squares. To improve the efficiency, blockwise SIFT matching is implemented in a parallel manner. Experiments demonstrate the effectiveness of the proposed approach. © 2006 IEEE.


Zhou Y.,Microsoft | Zhu X.,Xidian University | Fang Y.,University of Florida
IEEE Transactions on Mobile Computing | Year: 2010

Conventional block-based multicast authentication schemes overlook the heterogeneity of receivers by letting the sender choose the block size, divide a multicast stream into blocks, associate each block with a signature, and spread the effect of the signature across all the packets in the block through hash graphs or coding algorithms. The correlation among packets makes them vulnerable to packet loss, which is inherent in the Internet and wireless networks. Moreover, the lack of Denial of Service (DoS) resilience renders most of them vulnerable to packet injection in hostile environments. In this paper, we propose a novel multicast authentication protocol, namely MABS, including two schemes. The basic scheme (MABS-B) eliminates the correlation among packets and thus provides the perfect resilience to packet loss, and it is also efficient in terms of latency, computation, and communication overhead due to an efficient cryptographic primitive called batch signature, which supports the authentication of any number of packets simultaneously. We also present an enhanced scheme MABS-E, which combines the basic scheme with a packet filtering mechanism to alleviate the DoS impact while preserving the perfect resilience to packet loss. © 2010 IEEE.


Zhang R.-G.,Xidian University | Tan Y.-H.,Shanghai Normal University
Zhendong yu Chongji/Journal of Vibration and Shock | Year: 2012

A new approach for fault diagnosis of rolling element bearings was presented using the optimal Morlet wavelet and the statistical characteristic of the wavelet coefficients. It was shown that the optimization of the wavelet parameters benefits to extract the effective features. Thus, the criterion of the minimum Shannon entropy and the singular value decomposition technology were used to optimize the parameters of Morlet wavelet. The feature extraction firstly divided Morlet wavelet coefficients into a series of segments. Then, the infinite-norm of the covariance matrix for each segment was calculated, which was also used to construct the observation vectors of the hidden Markov model. Finally, the test results of bearing faults identification and isolation were presented and all the identification accuracies were greater than 93%.


Wang J.,Xidian University | Gouesbet G.,French National Center for Scientific Research
Applied Optics | Year: 2012

Localized beam models provide the most efficient and enlightening ways to evaluate beam shape coefficients of electromagnetic arbitrary shaped beams for use in light scattering theories. At the present time, they are valid in spherical and (circular and elliptical) cylindrical coordinates. A misuse of localized beam models in spherical coordinates recently appeared several times in the literature. We therefore present a warning to avoid the propagation of an incorrect use of localized beam models. © 2012 Optical Society of America.


Li F.,Xidian University | Shi G.,Xidian University | Wu F.,Microsoft
Proceedings - International Conference on Image Processing, ICIP | Year: 2011

Intra prediction with fine directions is a critical feature in the new High Efficiency Video Coding (HEVC) standard because it provides significant performance gain. Different from the intra prediction in the H.264/AVC, this approach is more complicated in terms of computation and memory access, which makes the VLSI design very difficult. In this paper, we propose an efficient uniform architecture for all of the 4x4 intra directional modes. The architecture is implemented by a register array and a flexible reference sample selection technique. This novel architecture does not need to project the samples from the side reference to the main reference. Thus, it reduces the processing latency and the number of registers considerably. The proposed architecture has been implemented with TSMC 0.13μm CMOS technology. Simulation results show that the proposed architecture only needs 9020 logic gates for 17 directional modes and can run at 150 MHz operation frequency. © 2011 IEEE.


Lan C.,Xidian University | Shi G.,Xidian University | Wu F.,Microsoft
IEEE Transactions on Image Processing | Year: 2010

Compound images are a combination of text, graphics and natural image. They present strong anisotropic features, especially on the text and graphics parts. These anisotropic features often render conventional compression inefficient. Thus, this paper proposes a novel coding scheme from the H.264 intraframe coding. In the scheme, two new intramodes are developed to better exploit spatial correlation in compound images. The first is the residual scalar quantization (RSQ) mode, where intrapredicted residues are directly quantized and coded without transform. The second is the base colors and index map (BCIM) mode that can be viewed as an adaptive color quantization. In this mode, an image block is represented by several representative colors, referred to as base colors, and an index map to compress. Every block selects its coding mode from two new modes and the previous intramodes in H.264 by rate-distortion optimization (RDO). Experimental results show that the proposed scheme improves the coding efficiency even more than 10 dB at most bit rates for compound images and keeps a comparable efficient performance to H.264 for natural images. © 2006 IEEE.


Qian L.P.,Zhejiang University of Technology | Qian L.P.,Xidian University | Zhang Y.J.A.,Chinese University of Hong Kong | Huang J.,Chinese University of Hong Kong | Wu Y.,Zhejiang University of Technology
IEEE Journal on Selected Areas in Communications | Year: 2013

This paper proposes a real-time pricing scheme that reduces the peak-to-average load ratio through demand response management in smart grid systems. The proposed scheme solves a two-stage optimization problem. On one hand, each user reacts to prices announced by the retailer and maximizes its payoff, which is the difference between its quality-of-usage and the payment to the retailer. On the other hand, the retailer designs the real-time prices in response to the forecasted user reactions to maximize its profit. In particular, each user computes its optimal energy consumption either in closed forms or through an efficient iterative algorithm as a function of the prices. At the retailer side, we develop a Simulated-Annealing-based Price Control (SAPC) algorithm to solve the non-convex price optimization problem. In terms of practical implementation, the users and the retailer interact with each other via a limited number of message exchanges to find the optimal prices. By doing so, the retailer can overcome the uncertainty of users' responses, and users can determine their energy usage based on the actual prices to be used. Our simulation results show that the proposed real-time pricing scheme can effectively shave the energy usage peaks, reduce the retailer's cost, and improve the payoffs of the users. © 1983-2012 IEEE.


Xu J.L.,New Jersey Institute of Technology | Su W.,U.S. Army | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2010

Automatic modulation recognition (AMR)-based software-defined radio (SDR) is a research challenge in developing third-generation (3G) and fourth-generation (4G) wireless communications with adaptive modulation capability. However, the existing AMR technology does not satisfy the seamless demodulation requirement of the SDR. A novel design of the AMR method with reduced computational complexity and fast processing speed is needed. This paper describes a discrete likelihood-ratio test (DLRT)-based rapid-estimation approach to identifying the modulation schemes blindly for uninterrupted data demodulation in real time. The statistical performance of the fast AMR associated with its implementation using the SDR is presented. © 2006 IEEE.


Zhang W.-G.,Xidian University | Pasalic E.,University of Primorska
IEEE Transactions on Information Theory | Year: 2014

In this paper, a novel approach of finding disjoint linear codes is presented. The cardinality of a set of [u, m, t+1] disjoint linear codes largely exceeds all the previous best known methods used for the same purpose. Using such sets of disjoint linear codes, not necessarily of the same length, we have been able to provide a construction technique of t-resilient S-boxes F:F{double-struck}2 n {mapping} F{double-struck} 2 m (n even, 1 < m ≤ ⌊n/4⌋) with strictly almost optimal nonlinearity > 2n-1-2n/2. This is the first time that the bound 2n-1-2n/2 has been exceeded by multiple output resilient functions. Actually, the nonlinearity of our functions is in many cases equal to the best known nonlinearity of balanced Boolean functions. A large class of previously unknown cryptographic resilient S-boxes is obtained, and several improvements of the original approach are proposed. Some other relevant cryptographic properties are also briefly discussed. It is shown that these functions may reach Siegenthaler's bound n-t-1, and can be either of optimal algebraic immunity or of slightly suboptimal algebraic immunity, which was confirmed by simulations. © 2014 IEEE.


Wang Z.,University of Waterloo | Wang Z.,Xidian University | Gong G.,University of Waterloo | Yu N.Y.,Lakehead University
IEEE Transactions on Information Theory | Year: 2013

In this paper, the sequence families of which maximum correlation is determined by the Weil bound of exponential sums are revisited. Using the same approach, two new constructions with large family sizes and low maximum correlation are given. The first construction is an analog of one recent result derived from the interleaved structure of Sidel'nikov sequences. For a prime p and an integer M\vert (p-1), the new m-ary sequence families of period p are obtained from irreducible quadratic polynomials and known power residue-based sequence families. The new sequence families increase family sizes of the known power residue-based sequence families, but keep the maximum correlation unchanged. In the second construction, the sequences derived from the Weil representation are generalized, where each new sequence is the elementwise product of a modulated Sidel'nikov sequence and a modulated trace sequence. For positive integers d


Wang Z.,Xidian University | Gong G.,University of Waterloo
IEEE Transactions on Information Theory | Year: 2011

A new elementary expression of the construction first proposed by Gurevich, Hadani, and Sochen is given, which avoids the explicit use of the Weil representation. The sequences in this signal set are given by both multiplicative character and additive character of finite field F p. Such a signal set consists of p 2(p-2) time-shift distinct sequences, the magnitude of the two-dimensional autocorrelation function (i.e., the ambiguity function) in both time and phase of each sequence is upper bounded by 2√p at any shift not equal to (0, 0). Furthermore, the magnitude of their Fourier transform spectrum is less than or equal to 2. For a subset consisting of p(p-2) phase-shift distinct sequences in this signal set, the magnitude of the ambiguity function of any pair is upper bounded by 4√p. A proof is given through finding a new expression of the sequences in the finite harmonic oscillator system. An open problem for directly establishing these assertions without involving the Weil representation is addressed. © 2011 IEEE.


Xie Y.,Shanghai Normal University | Xie Y.,Xidian University | Tan Y.,Shanghai Normal University | Dong R.,Shanghai Normal University
IEEE/ASME Transactions on Mechatronics | Year: 2013

In this paper, a modeling method of XY micropositioning stage with piezoelectric actuators is proposed. In the modeling scheme, a sandwich model consists of both input and output linear submodels, and an embedded neural-network-based hysteresis submodel is used to describe the motion behavior of each axis of the stage. Moreover, a neural-network-based submodel is constructed to describe the nonlinear interactive dynamics caused by the movement of another axis. Then, a tracking control scheme combined with a nonlinear decoupling control is proposed to compensate for the effect of the interactions between axes and track the reference trajectory. Then, the robust design method for the tracking and decoupling control is discussed. Finally, the experimental results on an XY micropositioning stage are presented. © 2012 IEEE.


Liu J.,Xidian University | Zhang Z.-J.,Xidian University | Yang Y.,Xi'an Jiaotong University
IEEE Signal Processing Letters | Year: 2012

Based on a diversely polarized antenna, we address the problems of adaptive detection and performance enhancement in partially homogeneous environments where the test and training data samples share the same noise covariance matrix up to an unknown scaling factor. The matched subspace detector and adaptive subspace detector are employed to handle the detection problem for the cases of known and unknown noise covariance matrix structure, respectively. The performance of the two detectors is evaluated in terms of their probabilities of false alarm and detection. In particular, a waveform design algorithm to enhance the detection performance of the two detectors is proposed. A numerical analysis is presented to demonstrate the potential performance improvement obtained with this algorithm. © 2011 IEEE.


Xu H.-X.,PLA Air Force Aviation University | Wang G.-M.,PLA Air Force Aviation University | Gong J.-Q.,Xidian University
Chinese Physics Letters | Year: 2012

A novel microstrip zeroth-order resonator (ZOR) antenna and its equivalent circuit model are exploited with two zeroth-order resonances. It is constructed based on a resonant-type composite right/left handed transmission line (CRLH TL) using a Wunderlich-shaped extended complementary single split ring resonator pair (W-ECSSRRP) and a series capacitive gap. The gap either can be utilized for double negative (DNG) ZOR antenna or be removed to engineer a simplified elision-negative ZOR (ENG) antenna. For verification, a DNG ZOR antenna sample is fabricated and measured. Numerical and experimental results agree well with each other, indicating that the omnidirectional radiations occur at two frequency bands which are accounted for by two shunt branches in the circuit model. The size of the antenna is 49% more compact than its previous counterpart. The superiority of W-ECSSRRP over CSSRRP lies in the lower fundamental resonance of the antenna by 38.2% and the introduction of a higher zeroth-order resonance. © 2012 Chinese Physical Society and IOP Publishing Ltd.


Li Q.,Xi'an Jiaotong University | Sun L.,Xi'an Jiaotong University | Bao L.,Xidian University
Expert Systems with Applications | Year: 2011

Enhanced index tracking is a popular strategy in portfolio management that focuses on adding reliable value relative to the index on the basis of mimicking the behavior of the benchmark index. In this paper, we propose a multi-objective optimization scheme for the enhanced index tracking problem, which provides the framework of defining the objectives as both maximizing the degree of beating the benchmark index and minimizing the accumulated error of underperforming the benchmark. Transaction costs are limited in the constraints. An immunity-based multi-objective optimization algorithm is presented to search for the solution of the enhanced index tracking problem. Treatment of infeasibility and solution selection are also presented. Our proposed approach is implemented to five data sets drawn from major world markets. The computational results compared with other published results show that our method has superior performance. © 2010 Elsevier Ltd. All rights reserved.


Lin Z.-Z.,Xidian University | Chen X.,Xi'an Jiaotong University
Physics Letters, Section A: General, Atomic and Solid State Physics | Year: 2013

The radiation-induced fragmentation of the C60 fullerene was investigated by the tight-binding electron-ion dynamics simulations. In intense laser field, the breathing vibrational mode is much more strongly excited than the pentagonal-pinch mode. The fragmentation effect was found more remarkable at long wavelength λ≥800 nm rather than the resonant wavelengths due to the internal laser-induced dipole force, and the production ratio of C and C2 rapidly grows with increasing wavelength. By such fragmentation law, C atoms, C2 dimers or large Cn fragments could be selectively obtained by changing the laser wavelength. And the fragmentation of C60 by two laser pulses like the multi-step atomic photoionization was investigated. © 2013 Elsevier B.V. All rights reserved.


Liu H.,Xidian University | Liu H.,Shanxi Datong University | Zhang J.,Xidian University
Applied Optics | Year: 2012

Because the dark current and the noise of quantum dot infrared photodetectors (QDIPs) can bring about a degradation in their performance, they have attracted more and more attention in recent years. In this paper, an algorithm used to evaluate the dark current of the QDIP is proposed, which is based on the algorithm including the common contribution of the microscale and the nanoscale electron transport. Namely, by accounting for the dependence of the drift velocity on the applied electric field, we greatly enhance the accuracy of the dark current calculation compared with that in the previous algorithm. This proposed algorithmis further used to estimate the noise current of QDIP, and the calculated results show a good agreement with the published data. © 2012 Optical Society of America.


Liu H.,Xidian University | Liu H.,Shanxi Datong University | Zhang J.,Xidian University
Infrared Physics and Technology | Year: 2012

Quantum dot infrared photodetectors (QDIPs) have already attracted more and more attention in recent years due to a high photoconductive gain, a low dark current and an increased operating temperature. In the paper, a device model for the QDIP is proposed. It is assumed that the total electron transport and the self-consistent potential distribution under the dark conditions determine the dark current calculation of QDIP devices in this model. The model can be used for calculating the dark current, the photocurrent and the detectivity of QDIP devices, and these calculated results show a good agreement with the published results, which illustrate the validity of the device model. © 2012 Elsevier B.V. All rights reserved.


Gao X.,Xidian University | Xiao B.,Xidian University | Tao D.,Nanyang Technological University | Li X.,University of London
Pattern Analysis and Applications | Year: 2010

Inexact graph matching has been one of the significant research foci in the area of pattern analysis. As an important way to measure the similarity between pairwise graphs error-tolerantly, graph edit distance (GED) is the base of inexact graph matching. The research advance of GED is surveyed in order to provide a review of the existing literatures and offer some insights into the studies of GED. Since graphs may be attributed or non-attributed and the definition of costs for edit operations is various, the existing GED algorithms are categorized according to these two factors and described in detail. After these algorithms are analyzed and their limitations are identified, several promising directions for further research are proposed. © Springer-Verlag London Limited 2009.


Sun G.,Xidian University | Xing M.,Xidian University | Xia X.-G.,University of Delaware | Wu Y.,CAS Institute of Electronics | Bao Z.,Xidian University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

Range cell migration (RCM) correction and azimuth spectrum being contained entirely in baseband are critical for ground moving-target imaging (GMTIm). Without the azimuth spectrum entirely contained within baseband and a proper RCM correction, the image will be defocused, or artifacts may appear in the image. An instantaneous-range-Doppler algorithm of GMTIm based on deramp-keystone processing is proposed. The main idea is to focus all the targets in the scene at an arbitrarily chosen azimuth time. With our proposed algorithm, RCMs of all targets in the scene are removed without a priori knowledge of their accurate motion parameters. The targets with azimuth spectrum not entirely in baseband, i.e., azimuth spectrum within an ambiguous pulse repeating frequency (PRF) band or spanning neighboring PRF bands, can also be effectively dealt with simultaneously. Theoretical analysis shows that no interpolation is needed. The simulated and real data are used to validate the effectiveness of this method. © 1980-2012 IEEE.


Yang J.,Southwest Jiaotong University | Yang J.,Xidian University | Fan P.,Southwest Jiaotong University | Duong T.Q.,Blekinge Institute of Technology | And 2 more authors.
IEEE Transactions on Wireless Communications | Year: 2011

The performance of two-way amplify-and-forward (AF) relaying networks over independently but not necessarily identically distributed (i.n.i.d.) Nakagami-m fading channels, with integer and integer plus one-half values of fading parameter m, is studied. Closed-form expressions for the cumulative distribution function (CDF), probability density function (PDF), and moment generating function (MGF) of the end-to-end signal-to-noise ratio (SNR) are presented. Utilizing these results, we analyze the performance of two-way AF relaying system in terms of outage probability, average symbol error rate (SER), and average sum-rate. Simulations are performed to verify the correctness of our theoretical analysis. © 2011 IEEE.


Li M.,PLA University of Science and Technology | Li M.,Engineering Corporation | Lin M.,Nanjing Institute of Technology | Yu Q.,PLA University of Science and Technology | And 3 more authors.
IEEE Journal on Selected Areas in Communications | Year: 2012

In this paper, a dual-hop multiple-input multiple-output (MIMO) amplify-and-forward (AF) relay network, where the source, relay and destination are each equipped with multiple antennas, is studied. By deriving and maximizing the receive signal-to-noise ratio (SNR) at the destination, we first obtain the optimal beamforming (BF) weights for the relay network. In order to evaluate the performance of the relay network, we then investigate the outage probability (OP), probability density function (PDF) and moments of the receive SNR as well as the ergodic capacity of the system in a closed-form. Furthermore, the average symbol error rate (ASER) expression of the relay network with the optimal transmit-receive BF is derived for three commonly used modulation formats, namely, M-ary pulse amplitude modulation (M-PAM), M-ary phase shift keying (M-PSK), and M-ary quadrature amplitude modulation (M-QAM). Finally, computer simulations are conducted to demonstrate the validity and efficacy of the designed MIMO relay network and its performance analysis. © 2012 IEEE.


Guo H.,Xidian University | Xie Q.-Y.,Lanzhou University | Fu C.-E.,Xi'an Jiaotong University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2015

Localization of a spin-1/2 fermion on the braneworld is an important and interesting problem. It is well known that a five-dimensional free massless fermion Ψ minimally coupled to gravity cannot be localized on the Randall-Sundrum braneworld. In order to trap such a fermion, the coupling between the fermion and bulk scalar fields should be introduced. In this paper, localization and quasilocalization of a bulk fermion on the thick braneworld generated by two scalar fields (a kink scalar φ and a dilaton scalar π) are investigated. Two types of couplings between the fermion and two scalars are considered. One coupling is the usual Yukawa coupling -ηΨ¯φΨ between the fermion and kink scalar, another one is λΨ¯ΓM∂Mπγ5Ψ between the fermion and dilaton scalar. The left-chiral fermion zero mode can be localized on the brane, and both the left- and right-chiral fermion massive Kaluza-Klein modes may be localized or quasilocalized. Hence the four-dimensional massless left-chiral fermion and massive Dirac fermions, whose lifetime is infinite or finite, can be obtained on the brane. © 2015 American Physical Society.


Li G.Y.,Georgia Institute of Technology | Niu J.,Xidian University | Lee D.,Georgia Institute of Technology | Fan J.,Xi'an Jiaotong University | Fu Y.,Huawei
IEEE Communications Surveys and Tutorials | Year: 2014

This paper provides an overview of multi-cell coordinated scheduling and multiple-input multiple-output (MIMO) techniques in LTE. We first discuss single-user MIMO (SU-MIMO) and multi-user MIMO (MU-MIMO) for LTE and identify potential techniques for further improving the performance of LTE, such as enhanced channel state information feedback and adaptive switching between SU-MIMO and MU-MIMO. Then, we address inter-cell interference mitigation techniques for downlink and uplink, respectively. Finally, potential research challenges and topics in the area are discussed. © 2014 IEEE.


Wang Y.-C.,Xidian University | Wang X.,Xidian University | Liu H.,Xidian University | Luo Z.-Q.,University of Minnesota
IEEE Transactions on Signal Processing | Year: 2012

Probing signal waveforms play a central role in the signal processing performance of a multiple-input multiple-output (MIMO) radar. In practice, for a given desired beam pattern, we need to design a probing signal waveform whose beam pattern closely matches the desired one and whose autocorrelation and cross-correlation sidelobes are kept low. The latter properties are important to mitigate undesirable interference caused by multiple targets or scatterers. In this correspondence, we present an efficient optimization method to design a constant modulus probing signal which can synthesize a desired beam pattern while maximally suppressing both the autocorrelation and cross-correlation sidelobes at/between given spacial angles. We formulate this problem as an unconstrained minimization of a fourth order trigonometric polynomial and propose an efficient quasi-Newton iterative algorithm to solve it. Besides, we provide an analysis of the local minima of the fourth-order trigonometric polynomial and prove that any local minima is a 1/2-approximation of its global optimal solution. Numerical examples show that the proposed approach compares favorably with the existing approach. © 2012 IEEE.


Liu J.,Xidian University | Zhang Z.-J.,Xidian University | Yang Y.,Xi'an Jiaotong University
Signal Processing | Year: 2012

In this paper, we address the performance optimization of adaptive detectors in Gaussian noise with unknown covariance matrix, based on a diversely polarized antenna (DPA). First, a general signal model is presented, where the system response is related to the characteristics of its transmitted pulses. Two adaptive detectors, i.e., generalized likelihood ratio and adaptive matched filter, are then adopted, and their expressions for the probabilities of false alarm and detection are provided. In particular, a waveform design algorithm to enhance the detection performance of both the detectors is proposed. Finally, simulation results illustrate the performance gain obtained with the proposed waveform design algorithm, i.e., by optimally selecting the polarization of the transmitted pulses of the DPA. © 2011 Elsevier B.V. All rights reserved.


Lin Z.-Z.,Xidian University | Chen X.,Xi'an Jiaotong University
Journal of Physics Condensed Matter | Year: 2013

A B-doped monatomic carbon chain has fine molecular capture ability for H2O and especially for NO2, which is better than that of other doped monatomic carbon chains. At 300 K and 1 atm, the capture probability of a B-doped monatomic carbon chain is appreciable even in a NO2 concentration of 1 ppm, and the influence of the adsorbate on the quantum transport is notable for the detection. In contrast, a pure monatomic carbon chain shows its invulnerability to N2, O2, H2O, NO2, CO and CO2, and is incapable of molecule capture due to having too low adsorption ability and weak response to quantum conductance. In the investigation of these issues, a statistic mechanical model (Lin et al 2011 Europhys. Lett. 94 40002; 2012 Chin. Phys. Lett. 29 080504) was extended to predict the adsorption and desorption rates of molecules on nanodevices. The theoretical foundation of this model was further discussed and its accuracy was verified by molecular dynamics simulations. © 2013 IOP Publishing Ltd.


Shi B.-Q.,Xidian University | Shi B.-Q.,Xi'an Jiaotong University | Liang J.,Xi'an Jiaotong University
Optics and Lasers in Engineering | Year: 2015

The processing technologies of multi-view range images (MRIs) scanned by three-dimensional (3D) laser scanners, structured light scanners and laser radars (Ladars) are current research hotspot. Most of the processing such as denoising, integration and surface reconstruction are performed in local neighborhood. Thus, fast and precise query of the local neighborhoods of the 3D point data in MRIs is very important. Due to measurement accuracy and alignment error, there are gaps in overlapping regions and through theoretical analysis and experimental verification, we notice that the gaps which may result in loss of local neighborhood information have great influence on the neighborhood query whereas the previous methods ignore it. Thereby, a novel local neighborhood which is named cylindrical neighborhood (CYND) is proposed. Its searching procedures are described in detail. Compared with the previous methods, our CYND expands the searching scope along the directions of normal vectors of the 3D point data, hence eliminating the impact of gaps. The widely used and well-implemented ANN library was employed for a comparison study and the experimental results demonstrate the validity and superiority of our CYND. With extensive application of 3D optical scanning technologies, this novel neighborhood will have a wide application prospect. © 2014 Elsevier Ltd. All rights reserved.


Liu J.,University of Posts and Telecommunications | Zhao F.,Shandong Institute of Business and Technology | Liu Y.,Xidian University
Pattern Recognition Letters | Year: 2013

Kernel Fisher discriminant analysis (KFDA) faces the problem of kernel parameters selection. A novel KFDA kernel parameters optimization criterion is presented for maximizing the uniformity of class-pair separabilities and class separability in kernel space simultaneously. The presented criterion is also applied to the kernel parameters selection of spectral regression kernel discriminant analysis (SRKDA). Minimum distance classifier, k nearest neighbor (kNN) classifier, and naive Bayes classifier are used to evaluate the feature extraction performance. Experiments on fourteen benchmark multiclass data sets show that, comparing with the criterion for merely maximizing the class separability in kernel space, the presented criterion can search the optimum KFDA kernel parameters more accurately, and do better in SRKDA kernel parameters selection. © 2013 Elsevier B.V. All rights reserved.


Liu H.,Xidian University | Liu H.,Shanxi Datong University | Zhang J.,Xidian University
Optics and Laser Technology | Year: 2012

Dark current has attracted much attention in recent years due to its great influence on the performance of the QDIP. In this paper, a model for the dark current is proposed with the consideration of the influence of the nanoscale electron transport on the dark current based on the dark current model proposed by H.C. Liu. The model permits calculating the dark current as a function of the electric field, and it can further estimate the photocurrent, the current responsivity and the detectivity via the current equilibrium equation under the dark condition. The results obtained show a good agreement with the experimental results and manifest the validity of the proposed model. © 2011 Elsevier Ltd. All rights reserved.


Zhou Z.,Southwest Jiaotong University | Zhou Z.,Xidian University | Tang X.,Southwest Jiaotong University | Niu X.,Southwest Jiaotong University | Parampalli U.,University of Melbourne
IEEE Transactions on Information Theory | Year: 2012

In this paper, the partial Hamming correlation properties of frequency-hopping sequences (FHSs) are discussed. The Peng-Fan bounds on sets of FHSs are generalized to the case of partial correlation. Both individual FHSs with optimal partial autocorrelation and sets of FHSs with optimal partial correlation are presented. The former has more new parameters compared with the known individual FHSs with optimal partial autocorrelation, while the later is obtained in the literature for the first time. © 2006 IEEE.


Mitri F.G.,Chevron | Li R.X.,Xidian University | Guo L.X.,Xidian University | Ding C.Y.,Xidian University
Annals of Physics | Year: 2015

A complete description of vector Bessel (vortex) beams in the context of the generalized Lorenz-Mie theory (GLMT) for the electromagnetic (EM) resonance scattering by a dielectric sphere is presented, using the method of separation of variables and the subtraction of a non-resonant background (corresponding to a perfectly conducting sphere of the same size) from the standard Mie scattering coefficients. Unlike the conventional results of standard optical radiation, the resonance scattering of a dielectric sphere in air in the field of EM Bessel beams is examined and demonstrated with particular emphasis on the EM field's polarization and beam order (or topological charge). Linear, circular, radial, azimuthal polarizations as well as unpolarized Bessel vortex beams are considered. The conditions required for the resonance scattering are analyzed, stemming from the vectorial description of the EM field using the angular spectrum decomposition, the derivation of the beam-shape coefficients (BSCs) using the integral localized approximation (ILA) and Neumann-Graf's addition theorem, and the determination of the scattering coefficients of the sphere using Debye series. In contrast with the standard scattering theory, the resonance method presented here allows the quantitative description of the scattering using Debye series by separating diffraction effects from the external and internal reflections from the sphere. Furthermore, the analysis is extended to include rainbow formation in Bessel beams and the derivation of a generalized formula for the deviation angle of high-order rainbows. Potential applications for this analysis include Bessel beam-based laser imaging spectroscopy, atom cooling and quantum optics, electromagnetic instrumentation and profilometry, optical tweezers and tractor beams, to name a few emerging areas of research. © 2015 Elsevier Inc..


Liu J.,Xidian University | Zhang Z.-J.,Xidian University | Yang Y.,Xi'an Jiaotong University | Liu H.,Xidian University
IEEE Transactions on Signal Processing | Year: 2011

In this paper, we consider the problem of detecting a signal in Gaussian noise with unknown covariance matrix, in partially homogeneous environments where the test and training data samples share the same noise covariance matrix up to an unknown scaling factor. One solution to this problem is the adaptive subspace detector (ASD) with a single or multiple observations. However, the probabilities of false alarm and detection of this ASD have not been obtained yet. In this paper, these expressions are derived on the basis of a single observation, which are confirmed with Monte Carlo simulations. It is shown that the ASD has a constant false alarm rate property with respect to both the shared noise covariance matrix structure and the independent scaling of the noise in the test data. In addition, we prove that for the First-Order model where the signal of interest is assumed to be a deterministic but unknown vector, the ASD derived with the generalized likelihood ratio test is consistent with that derived with an ad hoc two-step design procedure. © 2011 IEEE.


Zhou Z.,Southwest Jiaotong University | Zhou Z.,Xidian University | Tang X.,Southwest Jiaotong University | Wu D.,Guangxi Normal University | Yang Y.,Southwest Jiaotong University
IEEE Transactions on Information Theory | Year: 2012

Zero-difference balanced (ZDB) functions were introduced recently by Ding for the construction of optimal constant-composition codes, and optimal and perfect difference systems of sets. They are closely related to partitioned difference families. In this paper, we present generic constructions of ZDB functions from functions with difference-balanced property. In particular, two classes of ZDB functions with new and flexible parameters are reported. Employing these new ZDB functions, we obtain at the same time optimal (1) constant-composition codes, (2) constant-weight codes, and (3) perfect difference systems of sets, all with new and flexible parameters. © 2006 IEEE.


Guo H.,Xidian University | Ge J.,Xidian University | Ge J.,Henan Polytechnic University
Electronics Letters | Year: 2011

The overall outage probability of a two-way amplify-and-forward relaying system with opportunistic relay selection is investigated over Nakagami-m fading channels, and a tight closed-form approximation is derived. Further, closed-form expressions for the overall diversity and coding gains are obtained. Simulation results are presented to verify the analysis. Using these expressions, one can evaluate the outage performance, diversity and coding gains of a two-way relaying system easily and fast. © 2011 The Institution of Engineering and Technology.


Wang Y.-C.,Xidian University | Luo Z.-Q.,University of Minnesota
IEEE Transactions on Communications | Year: 2011

Iterative clipping and filtering (ICF) is a widely used technique to reduce the peak-to-average power ratio (PAPR) of orthogonal frequency division multiplexing (OFDM) signals. However, the ICF technique, when implemented with a fixed rectangular window in the frequency-domain, requires many iterations to approach specified PAPR threshold in the complementary cumulative distribution function (CCDF). In this paper, we develop an optimized ICF method which determines an optimal frequency response filter for each ICF iteration using convex optimization techniques. The design of optimal filter is to minimize signal distortion such that the OFDM symbol's PAPR is below a specified value. Simulation results show that our proposed method can achieve a sharp drop of CCDF curve and reduce PAPR to an acceptable level after only 1 or 2 iterations, whereas the classical ICF method would require 8 to 16 iterations to achieve a similar PAPR reduction. Moreover, the clipped OFDM symbols obtained by our optimized ICF method have less distortion and lower out-of-band radiation than the existing method. © 2011 IEEE.


Xing K.,Xi'an Jiaotong University | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University | Wang F.,Xi'an Jiaotong University | And 2 more authors.
IEEE Transactions on Systems, Man, and Cybernetics Part A:Systems and Humans | Year: 2011

The resource-transition circuit ( RTC) and siphon are two different structural objects of Petri nets and used to develop deadlock control policies for automated manufacturing systems. They are related to the liveness property of Petri net models and thus used to characterize and avoid deadlocks. Based on them, there are two kinds of methods for developing deadlock controllers. Such methods rely on the computation of all maximal perfect RTCs and strict minimal siphons (SMSs), respectively. This paper concentrates on a class of Petri nets called a system of simple sequential processes with resources, establishes the relation between two kinds of control methods, and identifies maximal perfect RTCs and SMSs. A graph-based technique is used to find all elementary RTC structures. They are then used to derive all RTCs. Next, an iterative method is developed to recursively construct all maximal perfect RTCs from elementary ones. Finally, a one-to-one correspondence between SMSs and maximal perfect RTCs and, hence, an equivalence between two deadlock control methods are established. © 2006 IEEE.


Gong M.,Xidian University | Fu B.,Xidian University | Jiao L.,Xidian University | Du H.,Xi'an Jiaotong University
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2011

Community structure is one of the most important properties in networks, and community detection has received an enormous amount of attention in recent years. Modularity is by far the most used and best known quality function for measuring the quality of a partition of a network, and many community detection algorithms are developed to optimize it. However, there is a resolution limit problem in modularity optimization methods. In this study, a memetic algorithm, named Meme-Net, is proposed to optimize another quality function, modularity density, which includes a tunable parameter that allows one to explore the network at different resolutions. Our proposed algorithm is a synergy of a genetic algorithm with a hill-climbing strategy as the local search procedure. Experiments on computer-generated and real-world networks show the effectiveness and the multiresolution ability of the proposed method. © 2011 American Physical Society.


Lin Z.-Z.,Xidian University | Chen X.,Xi'an Jiaotong University
Materials and Design | Year: 2016

Single-layer germanene was proposed as substrate for single-atom transition metal catalysts with much larger adsorption energies and higher thermal migration barriers than graphene. By density functional theory calculations, the electronic properties, thermal stabilities and catalytic abilities of Au, Fe, Ni, Pd, Pt and Ru adatoms on single-layer germanene were theoretically investigated. The results indicate that the CO contamination in H2 could be transformed into HCHO under the catalysis of Fe and Ru adatoms. For Fe and Ru adatoms, the three-step catalytic reactions were found both thermodynamically and kinetically favorable, with stable reaction intermediates and low potential barriers. Furthermore, Fe and Ru adatoms could be stably adsorbed on germanene with large adsorption energies and high thermal migration barriers, preventing the aggregation of Fe and Ru on germanene. However, for Au, Ni, Pd and Pt adatoms, the reaction intermediates are thermodynamically unfavorable so that the catalytic reactions should be difficult to proceed. By contrast, Fe and Ru adatoms on single-layer germanene should be excellent catalysts for removing the CO contamination from H2 feed gas of fuel cells. © 2016 Elsevier Ltd.


Wang H.-M.,Xi'an Jiaotong University | Liu F.,Xi'an Jiaotong University | Xia X.-G.,Xidian University | Xia X.-G.,University of Delaware
IEEE Transactions on Information Forensics and Security | Year: 2014

In this paper, we investigate the security issue of a two-hop amplify-and-forward multiple-input multiple-output wireless relay network in the existence of a multiantenna eavesdropper. The optimal scheme to achieve the secrecy capacity involves a nonconvex optimization and is still an open problem. Aiming to find an efficient way to enhance the secrecy rate with a tractable complexity, we propose a suboptimal joint source and relay linear precoding and power allocation scheme. In the scheme, the source node adopts a generalized singular value decomposition (SVD)-based precoding to transmit the signal in the first phase, and the relay node forwards the received signal based on the SVD precoding in the null-space of the wiretap channel in the second phase. Power allocations in both phases are optimized to maximize the secrecy rate by an alternating iterative optimization algorithm. Each iteration involves two subproblems. One has a water-filling solution and the other has a closed-form solution or a water-filling-like solution as well, both of which are computationally very efficient. The iteration converges fast and we prove that it guarantees to find a stationary optimum. Furthermore, we show that when the eavesdropper has equal or more antennas than the source does, the secrecy rate is a quasi-concave function of the source power so that allocating all the source power is generally not optimal. Numerical evaluation results are provided to show the effectiveness of the iterative algorithm and the proposed secrecy scheme. © 2014 IEEE.


Guo H.,Xidian University | Guo H.,Henan Polytechnic University | Ge J.H.,Xidian University
Electronics Letters | Year: 2010

The exact outage probability expression of two-way opportunistic relaying systems in amplify-and-forward strategy is presented, and a tight closed-form lower bound is obtained too. Simulation results are in excellent agreement with the derived expression and show that the signal-to-noise ratio gap between the lower bound and the actual performance is less than 1dB. © 2010 The Institution of Engineering and Technology.


Guo H.,Xidian University | Guo H.,Henan Polytechnic University | Ge J.,Xidian University | Ding H.,Xidian University
IEEE Communications Letters | Year: 2011

The overall outage probability (OOP) and symbol error probability (SEP) of a two-way amplify-and-forward (AF) relaying system are investigated. Tight closed-form expressions for the OOP and average SEP are derived for single-relay two-way AF systems. Further, in the case of multiple-relay two-way relaying, a tight closed-form expression for the OOP and an asymptotic approximation to the average SEP are obtained, respectively. Using these expressions, one can evaluate the outage and SEP performance of a two-way relaying system easily and fast. © 2011 IEEE.


Li Y.,Xi'an Jiaotong University | Li Y.,Xidian University | Yin Q.,Xi'an Jiaotong University | Xu W.,Xi'an Jiaotong University | Wang H.-M.,Xi'an Jiaotong University
IEEE Transactions on Wireless Communications | Year: 2011

Opportunistic relay selection is considered as an efficient approach to implement cooperative communication in multi-relay cooperative networks owing to its low implementation complexity. However, due to channel fluctuations, the channel state information (CSI) employed in relay selection process may differ from the exact CSI in data forwarding, in other words, the CSI is outdated. Addressing this issue, this paper focuses on the design of relay selection strategies in decode-and-forward (DF) cooperative networks with outdated CSIs being available in relay judgement, as well as their performance analysis. We resort to two main cases, 1) only outdated CSIs are available in relay selection process; 2) both outdated CSIs and statistical channel information are available in selection procedure, and propose three different relay selection schemes. The expressions of outage probability are derived, and asymptotic analysis in high SNR region is also carried out. Simulation results are finally provided, which not only validate our theoretical analysis, but also shed light on the way of designing relay selection strategies in various scenarios. © 2006 IEEE.


Xu H.-X.,PLA Air Force Aviation University | Wang G.-M.,PLA Air Force Aviation University | Chen X.,Xidian University | Li T.-P.,PLA Air Force Aviation University
IEEE Microwave and Wireless Components Letters | Year: 2012

In this letter, a compact balun with bandwidth enhancement is firstly proposed based on fully artificial fractal- shaped composite right/left handed transmission line (CRLH TL). It consists of three -90° CRLH branches and one +90° CRLH branch. The left handed contribution is realized by chip components while the right handed part is exploited by fractal microstriplines in terms of miniaturization. For verification, a balun operating at 1.5 GHz is designed, fabricated, and measured. Numerical and measured results agree well, which has confirmed the design concept and the derived formulae. The fabricated balun exhibits a bandwidth of 83.3% from 1 to 2.25 GHz, characterized by return loss better than 10 dB, amplitude and phase imbalance varied within ± 1 dB and ± 3.4°. Moreover, the circuit footprint is only 24.5% of the area that its conventional counterpart occupies. © 2006 IEEE.


Xiong T.,Xidian University | Xing M.,Xidian University | Xia X.-G.,University of Delaware | Bao Z.,Xidian University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2013

A novel method to obtain the formulations of the return signals in the 2-D frequency domain for both monostatic and bistatic synthetic aperture radar (SAR) is proposed. In this study, the squinted effective wavelength (SEW) is firstly used, so that the 2-D spectrums can be derived directly from their imaging geometries. For monostatic SAR (MoSAR), the 2-D spectrum is obtained without a lengthy derivation by using the widely-used principle of stationary phase. For the bistatic SAR (BiSAR), based on the assumption that the azimuth time durations of the transmitter and the receiver are the same, two individual SEWs can be derived, as well as the 2-D spectrums that are both concise and of high accuracy. Then, two modified omega-K algorithms based on the two 2-D spectrums are developed to process MoSAR and translational-invariant BiSAR data. Furthermore, as important processing steps of the proposed omega-K algorithms, a modified reference function multiplication and a modified Stolt mapping, which are much more suitable for SAR data processing than the conventional ones, are proposed. Simulations under a wide range of MoSAR and BiSAR system parameters are conducted. Finally, the proposed algorithms are applied to the analysis of acquired data and the results confirm not only the validity of the derived 2-D spectrums for both MoSAR and BiSAR but also the effectiveness of the proposed method. © 2012 IEEE.


Wu G.,Xidian University | Parker M.G.,University of Bergen
Cryptography and Communications | Year: 2014

We propose a construction for complementary sets of arrays that exploits a set of mutually-unbiased bases (a MUB). In particular we present, in detail, the construction for complementary pairs that is seeded by a MUB of dimension 2, where we enumerate the arrays and the corresponding set of complementary sequences obtained from the arrays by projection. We also sketch an algorithm to uniquely generate these sequences. The pairwise squared inner-product of members of the sequence set is shown to be 1/2. Moreover, a subset of the set can be viewed as a codebook that asymptotically achieves √3/2 times the Welch bound. © 2013 Springer Science+Business Media New York.


Cao K.,Michigan State University | Cao K.,Xidian University | Liu E.,Zhejiang University | Jain A.K.,Michigan State University | Jain A.K.,Korea University
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2014

Latent fingerprint matching has played a critical role in identifying suspects and criminals. However, compared to rolled and plain fingerprint matching, latent identification accuracy is significantly lower due to complex background noise, poor ridge quality and overlapping structured noise in latent images. Accordingly, manual markup of various features (e.g., region of interest, singular points and minutiae) is typically necessary to extract reliable features from latents. To reduce this markup cost and to improve the consistency in feature markup, fully automatic and highly accurate ('lights-out' capability) latent matching algorithms are needed. In this paper, a dictionary-based approach is proposed for automatic latent segmentation and enhancement towards the goal of achieving 'lights-out' latent identification systems. Given a latent fingerprint image, a total variation (TV) decomposition model with fidelity regularization is used to remove piecewise-smooth background noise. The texture component image obtained from the decomposition of latent image is divided into overlapping patches. Ridge structure dictionary, which is learnt from a set of high quality ridge patches, is then used to restore ridge structure in these latent patches. The ridge quality of a patch, which is used for latent segmentation, is defined as the structural similarity between the patch and its reconstruction. Orientation and frequency fields, which are used for latent enhancement, are then extracted from the reconstructed patch. To balance robustness and accuracy, a coarse to fine strategy is proposed. Experimental results on two latent fingerprint databases (i.e., NIST SD27 and WVU DB) show that the proposed algorithm outperforms the state-of-the-art segmentation and enhancement algorithms and boosts the performance of a state-of-the-art commercial latent matcher. © 1979-2012 IEEE.


Wang L.X.,Xidian University | Lin H.J.,China Academy of Space Technology
Microwave Journal | Year: 2013

This article presents a new dual passband filter using hybrid microstrip split ring resonators and coplanar waveguide (CPW) quarter wavelength resonators. Its equivalent RLC circuit model is presented, in which the parameters are extracted from the theoretical analysis and the measured S-parameters. The proposed filter has two passbands with center frequencies of 2.44 and 3.5 GHz. Good agreement between the equivalent circuit (EC), the electromagnetic (EM) simulated and the measured results is demonstrated.


Hou R.,Xidian University | Lui K.-S.,University of Hong Kong | Baker F.,Cisco Systems | Li J.,Xidian University
IEEE Transactions on Mobile Computing | Year: 2012

Wireless Mesh Network (WMN) has become an important edge network to provide Internet access to remote areas and wireless connections in a metropolitan scale. In this paper, we study the problem of identifying the maximum available bandwidth path, a fundamental issue in supporting quality-of-service in WMNs. Due to interference among links, bandwidth, a well-known bottleneck metric in wired networks, is neither concave nor additive in wireless networks. We propose a new path weight which captures the available path bandwidth information. We formally prove that our hop-by-hop routing protocol based on the new path weight satisfies the consistency and loop-freeness requirements. The consistency property guarantees that each node makes a proper packet forwarding decision, so that a data packet does traverse over the intended path. Our extensive simulation experiments also show that our proposed path weight outperforms existing path metrics in identifying high-throughput paths. © 2012 IEEE.


Miao Q.-G.,Xidian University | Shi C.,Xidian University | Xu P.-F.,Xidian University | Yang M.,Xidian University | Shi Y.-B.,Xi'an University of Technology
Optics Communications | Year: 2011

As a novel MGA (Multiscale Geometric Analysis) tool, shearlets are equipped with a rich mathematical structure similar to wavelets, which are associated to a multi-resolution analysis. Recently, shearlets have been used in image denoising, sparse image representation and edge detection. In this paper, as shearlet transform has the features of directionality, localization, anisotropy and multiscale, it is introduced into image fusion to obtain a fused image. The image could be decomposed by shearlet transform in any scale and any direction, and the detail information can be caught easily. Several different experiments are adopted to demonstrate that the fusion results based on shearlet transform contain more detail and smaller distortion information than any other methods does. © 2010 Elsevier B.V. All rights reserved.


Gao X.,Xidian University | Zhang K.,Xidian University | Tao D.,Xihua University | Li X.,Intelligent Systems Technology, Inc. | Li X.,CAS Xi'an Institute of Optics and Precision Mechanic
IEEE Transactions on Image Processing | Year: 2012

Until now, neighbor-embedding-based (NE) algorithms for super-resolution (SR) have carried out two independent processes to synthesize high-resolution (HR) image patches. In the first process, neighbor search is performed using the Euclidean distance metric, and in the second process, the optimal weights are determined by solving a constrained least squares problem. However, the separate processes are not optimal. In this paper, we propose a sparse neighbor selection scheme for SR reconstruction. We first predetermine a larger number of neighbors as potential candidates and develop an extended Robust-SL0 algorithm to simultaneously find the neighbors and to solve the reconstruction weights. Recognizing that the k-nearest neighbor (k-NN) for reconstruction should have similar local geometric structures based on clustering, we employ a local statistical feature, namely histograms of oriented gradients (HoG) of low-resolution (LR) image patches, to perform such clustering. By conveying local structural information of HoG in the synthesis stage, the k-NN of each LR input patch is adaptively chosen from their associated subset, which significantly improves the speed of synthesizing the HR image while preserving the quality of reconstruction. Experimental results suggest that the proposed method can achieve competitive SR quality compared with other state-of-the-art baselines. © 2012 IEEE.


Li J.,Guangzhou University | Chen X.,Xidian University
Computing and Informatics | Year: 2013

As cloud computing becomes prevalent, more and more sensitive information are being centralized into the cloud. For the protection of data privacy, sensitive data usually have to be encrypted before outsourcing, which makes effective data utilization a very challenging task. In this paper, we propose a new method to enable effective fuzzy keyword search in a multi-user system over encrypted cloud data while maintaining keyword privacy. In this new system, differential searching privileges are supported, which is achieved with the technique of attribute-based encryption. Edit distance is utilized to quantify keywords similarity and develop fuzzy keyword search technique, which achieve optimized storage and representation overheads. We further propose a symbol-based trie-traverse searching scheme to improve the search efficiency. Through rigorous security analysis, we show that our proposed solution is secure and privacy-preserving, while correctly realizing the goal of fuzzy keyword search with multiple users.


Liu Y.,Xidian University | Xia X.-G.,University of Delaware | Zhang H.,Xidian University
IEEE Transactions on Wireless Communications | Year: 2013

In this paper, a two-relay full-duplex asynchronous cooperative network with the amplify-and-forward (AF) protocol is considered. We propose two distributed space-time coding schemes for the cases with and without cross-talks, respectively. In the first case, each relay can receive the signal sent by the other through the cross-talk link. We first study the feasibility of cross-talk cancellation in this network and show that the cross-talk interference cannot be removed well. For this reason, we design space-time codes by utilizing the cross-talk signals instead of removing them. In the other case, the self-coding is realized individually through the loop channel at each relay node and the signals from the two relay nodes form a space-time code. The achievable cooperative diversity of both cases is investigated and the conditions to achieve full cooperative diversity are presented. Simulation results verify the theoretical analysis. © 2013 IEEE.


Han Y.P.,Xidian University | Cui Z.W.,Xidian University | Gouesbet G.,INSA Rouen
Journal of Quantitative Spectroscopy and Radiative Transfer | Year: 2012

An efficient numerical method based on the surface integral equations is introduced to simulate the scattering of Gaussian beam by complex particles that consist of an arbitrarily shaped host particle and multiple internal inclusions of arbitrary shape. In particular, the incident focused Gaussian beam is described by the Davis fifth-order approximate expressions in combination with rotation defined by Euler angles. The established surface integral equations are discretized with the method of moments, where the unknown equivalent electric and magnetic currents induced on the surfaces of the host particle and the internal inclusions are expanded using the Rao-Wilton-Glisson (RWG) basis functions. The resultant matrix equations are solved by using the parallel conjugate gradient method. The proposed numerical method is validated and its capability illustrated in several characteristic examples. © 2012 Elsevier Ltd.


Li Y.,Xidian University | Zhang L.,Xidian University | Cimini Jr. L.J.,Alcatel - Lucent | Zhang H.,University of Delaware
IEEE Transactions on Signal Processing | Year: 2011

Multiple-input multiple-output (MIMO) beamforming (MBF) can greatly increase the signal gain and reduce the effects of multipath fading for cell-edge users. The objective of this work is to investigate the impact of co-channel unequal-power MIMO interferers on an MBF desired receiver under realistic propagation conditions, including path-loss and Rayleigh fading. Two major contributions are made in this work: i) for the co-channel interference term in the signal-to-interference ratio (SIR) expressions, a closed-form expression of the probability density function (PDF) is derived; ii) for the desired signal term, a simple approximation is proposed. Moreover, closed-form PDF expressions for the SIRs are obtained for some special cases. Simulation results verify the validity of the theoretical analyses. © 2011 IEEE.


Chen G.,Xidian University | Xiong B.,Xidian University | Huang X.,Polytechnic University of Mozambique
Precision Engineering | Year: 2011

Compliant mechanisms have been used in many engineering areas where high precision and sensitivity are required. One of the major challenges of designing compliant mechanisms lies in understanding and analyzing the nonlinear deflections of flexible members. The pseudo-rigid-body model (PRBM) method, which simplifies the modeling of the nonlinear deflection by approximating it as motion of rigid links, has been accepted as one of the most important tools for synthesis and analysis of compliant mechanisms. In this paper, a review of various PRBMs is presented. The 3R PRBM whose characteristic parameters are independent of external loads is discussed in detail. For the purpose of finding the optimal set of the characteristic parameters for the 3R PRBM, a six-dimensional objective function is formulated by combining the approximation errors of both tip point and tip slope for the two extreme load cases, i.e., pure moment load and pure vertical force load. A particle swarm optimizer was employed to conduct a continuous search on the objective function. The resulting 3R PRBM with the optimized characteristic parameters shows better performance in predicting large deflections of cantilever beams over the original 3R PRBM. © 2011 Elsevier Inc.


Zhang L.,Soochow University of China | Zhou W.-D.,AI Speech Ltd. | Chang P.-C.,Yuan Ze University | Liu J.,Xidian University | And 3 more authors.
IEEE Transactions on Signal Processing | Year: 2012

Sparse representation-based classifier (SRC), a combined result of machine learning and compressed sensing, shows its good classification performance on face image data. However, SRC could not well classify the data with the same direction distribution. The same direction distribution means that the sample vectors belonging to different classes distribute on the same vector direction. This paper presents a new classifier, kernel sparse representation-based classifier (KSRC), based on SRC and the kernel trick which is a usual technique in machine learning. KSRC is a nonlinear extension of SRC and can remedy the drawback of SRC. To make the data in an input space separable, we implicitly map these data into a high-dimensional kernel feature space by using some nonlinear mapping associated with a kernel function. Since this kernel feature space has a very high (or possibly infinite) dimensionality, or is unknown, we have to avoid working in this space explicitly. Fortunately, we can indeed reduce the dimensionality of the kernel feature space by exploiting kernel-based dimensionality reduction methods. In the reduced subspace, we need to find sparse combination coefficients for a test sample and assign a class label to it. Similar to SRC, KSRC is also cast into an ℓ 1-minimization problem or a quadratically constrained ℓ 1 -minimization problem. Extensive experimental results on UCI and face data sets show KSRC improves the performance of SRC. © 2011 IEEE.


Chen J.,Polytechnic University of Mozambique | Chen J.,Xidian University | Ma L.,Polytechnic University of Mozambique
IET Radar, Sonar and Navigation | Year: 2011

Non-linear filter has been widely used in many applications, and particle filter (PF) is a promising approach because it can treat the non-linear and non-Gaussian system. If there are correlations between process noise and measurement noise in the non-linear system, the performance of general PF degenerates. The study addresses that there are correlated measurement and process noise at the same time in the non-linear system. Aiming at this problem, the authors decouple the correlation and rearrange the state transition equation to a new one, and remove the correlation. And then apply the general PF based on the new state transition equation and the original measurement equation. From the derivation, it is easy to know that the proposed method is equal to general PF when there are no correlated noises. Experimental results show that the proposed method outperforms the general PF when there are correlated noises. © 2011 The Institution of Engineering and Technology.


Cai N.,Xidian University | Chan T.,University of South Australia
Proceedings of the IEEE | Year: 2011

In this tutorial paper, we focus on the basic theory of linear secure network coding. Our goal is to present fundamental results and provide preliminary knowledge for anyone interested in the area. We first present a model for secure network coding and then a necessary and sufficient condition for a linear network code to be secure. Optimal methods to construct linear secure network codes are also provided. For further investigation of the secure properties of linear network codes, we illuminate different secure criteria and requirements, with a few alternative models. © 2006 IEEE.


Liu Y.,Xidian University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University | Zhang H.,Xidian University
IEEE Transactions on Wireless Communications | Year: 2012

In this paper, we propose two distributed linear convolutional space-time coding (DLC-STC) schemes for full-duplex (FD) asynchronous cooperative communications. The DLC-STC Scheme 1 is for the case of the complete loop channel cancellation, which achieves the full asynchronous cooperative diversity. The DLC-STC Scheme 2 is for the case of the partial loop channel cancellation and amplifying, where some loop signals are used as the self-coding instead of treated as interference to be directly cancelled. We show this scheme can achieve full asynchronous cooperative diversity. We then evaluate the performance of the two schemes when loop channel information is not accurate and present an amplifying factor control method for the DLC-STC Scheme 2 to improve its performance with inaccurate loop channel information. Simulation results show that the DLC-STC Scheme 1 outperforms the DLC-STC Scheme 2 and the delay diversity scheme if perfect or high quality loop channel information is available at the relay, while the DLC-STC Scheme 2 achieves better performance if the loop channel information is imperfect. © 2012 IEEE.


Chen X.,Nanjing University of Aeronautics and Astronautics | Chen X.,Xidian University | Yuen C.,Singapore University of Technology and Design | Zhang Z.,Zhejiang University
IEEE Transactions on Vehicular Technology | Year: 2014

In this paper, we consider a multiantenna system where the receiver should harvest energy from the transmitter by wireless energy transfer to support its wireless information transmission. To maximize the harvesting energy, we propose the performance of adaptive energy beamforming according to the instantaneous channel state information (CSI). To help the transmitter obtain the CSI for energy beamforming, we further propose a win-win CSI quantization feedback strategy to improve the efficiencies of both power and information transmission. The focus of this paper is on the tradeoff of wireless energy and information transfer by adjusting the transfer duration with a total duration constraint. By revealing the relationship between transmit power, transfer duration, and feedback amount, we derive two wireless energy and information transfer tradeoff schemes by maximizing an upper bound and an approximate lower bound of the average information transmission rate, respectively. Moreover, the impact of imperfect CSI at the receiver is investigated, and the corresponding wireless energy and information transfer tradeoff scheme is also given. Finally, numerical results validate the effectiveness of the proposed schemes. © 2013 IEEE.


Xun D.M.,Hunan University | Liu Q.H.,Hunan University | Zhu X.M.,Xidian University
Annals of Physics | Year: 2013

A generalization of Dirac's canonical quantization scheme for a system with second-class constraints is proposed, in which the fundamental commutation relations are constituted by all commutators between positions, momenta and Hamiltonian, so they are simultaneously quantized in a self-consistent manner, rather than by those between merely positions and momenta which leads to ambiguous forms of the Hamiltonian and the momenta. The application of the generalized scheme to the quantum motion on a torus leads to a remarkable result: the quantum theory is inconsistent if built up in an intrinsic geometric manner, whereas it becomes consistent within an extrinsic examination of the torus as a submanifold in three dimensional flat space with the use of the Cartesian coordinate system. The geometric momentum and potential are then reasonably reproduced. © 2013 Elsevier Inc.


Duan B.,Xidian University | Yang Y.,Xidian University | Zhang B.,University of Electronic Science and Technology of China
Solid-State Electronics | Year: 2010

A novel concept of REBULF (REduced BULk Field) is proposed for the developing smart power integrated circuit with the thin epitaxy layer. The REBULF LDMOS structure is designed with N+ buried layer embedded in the high-resistance substrate. The mechanism of breakdown of the new device is that the high electric field around the drain is reduced by N+ buried layer, which causes the redistribution of the bulk electric field in the drift region of the REBULF LDMOS so that the substrate supports more biases. The critical condition of the REBULF technology is analyzed and validated by 2-D MEDICI simulation results, which is the product of the location of N+ buried layer and substrate's doping is not more than 1 × 1012 cm -2. The breakdown voltage of REBULF LDMOS is increased by 75% in comparison to the conventional RESURF LDMOS from the simulation results. The experimental results show the high electric field around the drain is reduced as the depletion region spreads to N+ buried layer. Although the leakage has increased a little, this increase is not enough to cause the avalanche breakdown. Crown Copyright © 2010 Published by Elsevier Ltd. All rights reserved.


Dai Z.,Xidian University | Wang J.,Xidian University | Heng Y.,Shanghai Institute of Technology
Optics Express | Year: 2011

A method for synthesizing bandpass photonic crystal filters for wavelength division multiplexing (WDM) systems is presented. The proposed method permits the calculation of the physical dimensions of the crystalline structures given the desired frequency response of the filter in terms of bandwidth, in-band ripple, minimum out-of-band attenuation, and central frequency. The method, explained in detail for Chebyshev frequency responses, is equivalent circuit based. The resulting devices are very compact, have a high out-of-band attenuation, and are suitable for high density photonic integrated circuits. The validity of the proposed method is confirmed through contrasting the simulation concluded from the finitedifference time-domain (FDTD) method by the design of a third-order Chebyshev filter having a center frequency of 1THz, a flat bandwidth of 4GHz, and ripples of 0.5 dB in the passband. © 2011 Optical Society of America.


Ding S.,Dalian University of Technology | Ding S.,Dalian Nationalities University | Zhang S.,Xidian University | Li Y.,Dalian Nationalities University | Wang T.,Dalian University of Technology
Biochimie | Year: 2012

Knowledge of structural classes plays an important role in understanding protein folding patterns. In this paper, features based on the predicted secondary structure sequence and the corresponding E-H sequence are extracted. Then, an 11-dimensional feature vector is selected based on a wrapper feature selection algorithm and a support vector machine (SVM). Among the 11 selected features, 4 novel features are newly designed to model the differences between α/β class and α + β class, and other 7 rational features are proposed by previous researchers. To examine the performance of our method, a total of 5 datasets are used to design and test the proposed method. The results show that competitive prediction accuracies can be achieved by the proposed method compared to existing methods (SCPRED, RKS-PPSC and MODAS), and 4 new features are demonstrated essential to differentiate α/β and α + β classes. Standalone version of the proposed method is written in JAVA language and it can be downloaded from http://web.xidian.edu.cn/slzhang/ paper.html. © 2012 Elsevier Masson SAS. All rights reserved.


Zi B.,China University of Mining and Technology | Zhu Z.-C.,China University of Mining and Technology | Du J.-L.,Xidian University
Control Engineering Practice | Year: 2011

This paper is concerned with modeling, analysis, and control of the cable-supporting system including actuator dynamics for the next generation large spherical radio telescope. According to its 50-m scaled model, to begin with, the dynamic formulations of the electromechanical coupling system including servomechanism dynamics and parabolic curve of the long-span cable sag effects are established; at the same time the relationship among cable force, cable end displacement and cable length variation is obtained by utilizing parabolic equation, and the dynamic modeling for control can be justified by the numerical example. In addition, taking account of the characteristics of nonlinearity, slow time-variant and multivariable coupling, a fuzzy control plus proportional-integral control method is utilized to control the wind-induced vibration of the cable-supporting system. Finally, simulation results from the 50-m scaled model control system, regarding the wind-induced vibration control of the cable-supporting structure in stationary position and the tracking control of the cable-supporting system, show the satisfactory performance of the proposed control scheme as compared with a discrete-time automatic disturbances rejection controller in the presence of internal model uncertainties in both the cable-supporting mechanism and servomechanism dynamics and external disturbances. © 2011 Elsevier Ltd.


Tian G.,Northeast Forestry University | Chu J.,Northeast Forestry University | Hu H.,Xidian University | Li H.,Northeast Forestry University
Journal of Cleaner Production | Year: 2014

Due to its significant effects on energy-saving and emission reduction, automotive components remanufacturing (ACR) has become an important direction for Chinese industry's sustainable development. Current ACR industry in China is still in its growing stage, industrial technologies are a key factor to promote ACR industry development. This work introduces some basic concepts on ACR in China and analyses its roles. According to different ACR production types, characteristics of their operation modes are summarized and compared. In addition, based on basic conditions of products remanufacturing and status and challenges of ACR industry, some key technologies of developing China's ACR industry are proposed and presented. An integrated sketch of technology system for China's ACR industry development is also established. Finally, based on analytic hierarchy process (AHP), two case studies are presented to obtain main key technology factors influencing ACR industry development in China. This can provide some guidance for developing ACR industry in China and other developing countries. © 2014 Elsevier Ltd. All rights reserved.


Yan M.,University of Electronic Science and Technology of China | Zhong C.,Xidian University
International Journal of Production Research | Year: 2011

This paper focuses on the problem of deadlocks in automated flexible manufacturing systems (FMS). Based on Petri nets, a deadlock prevention policy is proposed for a special class of Petri nets, S 3PR. We embed the deadlock avoidance policy (DAP) of conjunctive/disjunctive resources upstream neighbourhood (C/D RUN) into the deadlock prevention policy (DPP), and allocate the underlying (sequential) resources reasonably to guarantee the absence of deadlock states and processes. First, siphons in a net model are distinguished by elementary and dependent ones. From the set of elementary siphons, a set of linear inequality constraints expressed by the state vector can be formalised. After being modified by the proposed policy, a set of generalised mutual exclusion constraints (GMEC) expressed by the marking vector can be found. Then monitors based on the GMEC are added to the plant model such that the elementary siphons in the S 3PR net are all invariant-controlled and no emptiable siphon is generated due to the addition of the monitors. This novel deadlock prevention policy can usually lead to a more permissive supervisor by adding a smaller number of monitors and arcs than the existing methods for the design of liveness-enforcing Petri net supervisors. Two manufacturing examples are utilised to illustrate the proposed method and compared with the existing ones. © 2011 Taylor & Francis.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2011

Three low-complexity relay-selection strategies, namely, selective amplify and forward (S-AF), selective decode and forward (S-DF), and amplify and forward with partial relay selection (PRS-AF) in a spectrum-sharing scenario are studied. First, we consider a scenario where perfect channel state information (CSI) is available. For these scenarios, the respective asymptotic outage behaviors of the secondary systems are analyzed, from which the diversity and coding gains are derived and compared. Unlike the coding gain, which is shown to be very sensitive with the position of the primary receiver, the diversity gain of the secondary system is the same as the nonspectrum-sharing system. In addition, depending on the cooperative strategy employed, an increase in the number of relays may lead to severe loss of the coding gain. Afterwards, the impacts of imperfect CSI regarding the interference and transmit channels on the outage behavior of the secondary systems are analyzed. On one hand, the imperfect CSI concerning the interference channels only affects the outage performance of the primary system, whereas it has no effect on the diversity gain of the secondary system. On the other hand, the imperfect CSI concerning the transmit channels of the secondary systems may reduce the diversity gain of the three relay-selection strategies to unity, which is validated by both theoretical and numerical results. © 2006 IEEE.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xidian University
IEEE Transactions on Vehicular Technology | Year: 2011

This paper proposes a new efficient scheme for the combined use of cooperative diversity and multiuser diversity. Considering a decode-and-forward (DF) opportunistic relaying strategy, we first study the outage behavior of the joint sourcerelay-selection scheme with/without direct links, from which the significance of the direct links is recognized. Motivated by the crucial role of these links on the system performance, a two-step selection scheme is proposed, which first selects the best source node based on the channel quality of the direct links and then selects the best link from the selected source to the destination. The proposed scheme significantly reduces the amount of channel estimation while achieving comparable outage performance to that using the joint selection scheme. Most importantly, the achieved diversity order is the same as that using the joint selection scheme. In addition, assuming an amplify-and-forward (AF) opportunistic relaying strategy, the outage behavior of this two-step scheme is also analyzed, and its availability is confirmed as well. © 2006 IEEE.


Ding H.,Xidian University | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará
IEEE Transactions on Vehicular Technology | Year: 2013

In this paper, we establish a two-user opportunistic cooperative framework, where two users compete to transmit their own information to a common destination. For such a framework, by relying on the instantaneous channel conditions, either of the two users can opportunely play the role of an information source, and the other user will serve as an amplify-and-forward (AF) relay. To enhance the transmission reliability in terms of system outage probability, an optimal and centralized role selection (C-ROSE) scheme is first proposed, which maximizes the received signal-to-noise ratio (SNR) at the destination. To alleviate the signaling overhead of C-ROSE, a distributed ROSE (D-ROSE) scheme is presented by invoking a local channel state information (CSI) exploitation/decision mechanism, which can lower the signaling overhead while maintaining almost the same outage performance as that of C-ROSE. With the user fairness in mind and owing to the distributed decision rule of D-ROSE, a proportional fair scheduling (PFS) strategy is incorporated into D-ROSE, such that the two users have an equal opportunity to act as a source. We refer to this new ROSE scheme as P-ROSE. To reveal the inherent impacts of different link statistics on the system outage behavior, closed-form lower and upper bound expressions are derived for the outage probability of the three ROSE schemes. Moreover, asymptotic outage analysis points out that the high-SNR outage behaviors of the three schemes are exactly the same and are dominated by the user-destination links, irrespective of the interuser link. Furthermore, both theoretical analysis and numerical results manifest that 1) under the scenario of balanced user-destination links, the outage performance of the three ROSE schemes are almost the same over the entire SNR regions and that 2) under the scenario of unbalanced user-destination links, the outage performance of P-ROSE is inferior to that of C-ROSE and D-ROSE from low-to-medium SNR regions, particularly in the case of a weak interuser link. In addition, representative numerical examples are shown to demonstrate the effects of node placement on the system outage performance, signaling overhead, and user fairness of the three ROSE schemes, from which the tradeoff between outage performance and user fairness of the three schemes are numerically examined. © 2013 IEEE.


Lv X.,Nanyang Technological University | Bi G.,Nanyang Technological University | Wan C.,DSO National Laboratories | Xing M.,Xidian University
IEEE Transactions on Signal Processing | Year: 2011

This paper proposes a novel representation, known as Lv's distribution (LVD), of linear frequency modulated (LFM) signals. It has been well known that a monocomponent LFM signal can be uniquely determined by two important physical quantities, centroid frequency and chirp rate (CFCR). The basic reason for expressing a LFM signal in the CFCR domain is that these two quantities may not be apparent in the time or time-frequency (TF) domain. The goal of the LVD is to naturally and accurately represent a mono- or multicomponent LFM in the CFCR domain. The proposed LVD is simple and only requires a two-dimensional (2-D) Fourier transform of a parametric scaled symmetric instantaneous autocorrelation function. It can be easily implemented by using the complex multiplications and fast Fourier transforms (FFT) based on the scaling principle. The computational complexity, properties, detection performance and representation errors are analyzed for this new distribution. Comparisons with three other popular methods, Radon-Wigner transform (RWT), Radon-Ambiguity transform (RAT), and fractional Fourier transform (FRFT) are performed. With several numerical examples, our distribution is demonstrated to be a CFCR representation that is computed without using any searching operation. The main significance of the LVD is to convert a 1-D LFM into a 2-D single-frequency signal. One of the most important applications of the LVD is to generate a new TF representation, called inverse LVD (ILVD), and a new ambiguity function, called Lv's ambiguity function (LVAF), both of which may break through the tradeoff between resolution and cross terms. © 2011 IEEE.


Cheng W.,Xidian University | Zhang X.,Texas A&M University | Zhang H.,Xidian University
Proceedings - IEEE INFOCOM | Year: 2013

We consider the full-duplex transmission over bidirectional channels with imperfect self-interference cancelation in wireless networks. In particular, together using propagation-domain interference suppression, analog-domain interference cancellation, and digital-domain interference cancellation, we develop the optimal dynamic power allocation schemes for the wireless full-duplex sum-rate optimization problem which aims at maximizing the sum-rate of wireless full-duplex bidirectional transmissions. In the high signal-to-interference-plus-noise ratio (SINR) region, the full-duplex sum-rate maximization problem is a convex optimization problem. For interference- dominated wireless full-duplex transmission in the high SINR region, we derive the closed-form expression for the optimal dynamic power allocation scheme. For non-interference-dominated wireless full-duplex transmission in the high SINR region, we obtain the optimal dynamic power allocation scheme by numerically solving the corresponding Karush-Kuhn-Tucker (KKT) conditions. While the full-duplex sum-rate maximization problem is usually not a convex optimization problem, by developing the tightest lower-bound function and using the logarithmic change of variables technique, we convert the full-duplex sum-rate maximization problem to a convex optimization problem. Then, using our proposed iteration algorithm, we can numerically derive the optimal dynamic power allocation scheme for the more generic scenario. Also presented are the numerical results which validate our developed optimal dynamic power allocation schemes. © 2013 IEEE.


Cheng W.,Xidian University | Zhang X.,Texas A&M University | Zhang H.,Xidian University
IEEE Journal on Selected Areas in Communications | Year: 2013

Spectrum and power efficiencies are both crucial to design efficient wireless networks. In past two decades, spectrum and power efficiencies of wireless networks are optimized separately. However, to increase the spectrum efficiency while reducing the energy consumption, it is necessary to jointly optimize spectrum and power efficiencies of wireless networks. Supporting the statistical quality of service (QoS) provisionings for real-time traffic is crucial, but imposes new challenges, in the next generation wireless networks. In this paper, we propose an efficient framework to jointly optimize effective spectrum efficiency (ESE) and effective power efficiency (EPE) under different statistical QoS guarantees constraints to support the real-time traffic over wireless networks. In particular, we derive the relationship between ESE and EPE under statistical QoS provisioning constraint. Based on this relationship, we obtain the mutually beneficial (MB) region and the contention-based (CB) region. In the MB region, we propose a novel strategy to achieve the joint effective spectrum and power efficiencies optimization using the average transmit power control. In the CB region, we propose the wireless-relay-based strategy to jointly optimize the effective capacity and power efficiency. In both MB and CB regions, we develop the dynamic transmit-power control strategy and the MIMO-based strategy to jointly maximize the effective spectrum and power efficiencies. Also conducted is a set of numerical evaluations showing that our proposed strategies can achieve superior joint spectrum and power efficiencies optimization for the diverse statistical QoS provisionings. © 1983-2012 IEEE.


Zhang L.,Xidian University | Qiao Z.-J.,University of Texas–Pan American | Xing M.,Xidian University | Li Y.,Xidian University | Bao Z.,Xidian University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2011

From the theory of compressive sensing (CS), we know that the exact recovery of an unknown sparse signal can be achieved from limited measurements by solving a sparsity-constrained optimization problem. For inverse synthetic aperture radar (ISAR) imaging, the backscattering field of a target is usually composed of contributions by a very limited amount of strong scattering centers, the number of which is much smaller than that of pixels in the image plane. In this paper, a novel framework for ISAR imaging is proposed through sparse stepped-frequency waveforms (SSFWs). By using the framework, the measurements, only at some portions of frequency subbands, are used to reconstruct full-resolution images by exploiting sparsity. This waveform strategy greatly reduces the amount of data and acquisition time and improves the antijamming capability. A new algorithm, named the sparsity-driven High-Resolution Range Profile (HRRP) synthesizer, is presented in this paper to overcome the error phase due to motion usually degrading the HHRP synthesis. The sparsity-driven HRRP synthesizer is robust to noise. The main novelty of the proposed ISAR imaging framework is twofold: 1) dividing the motion compensation into three steps and therefore allowing for very accurate estimation and 2) both sparsity and signal-to-noise ratio are enhanced dramatically by coherent integrant in cross-range before performing HRRP synthesis. Both simulated and real measured data are used to test the robustness of the ISAR imaging framework with SSFWs. Experimental results show that the framework is capable of precise reconstruction of ISAR images and effective suppression of both phase error and noise. © 2011 IEEE.


Cheng W.,Texas A&M University | Zhang X.,Texas A&M University | Zhang H.,Xidian University
Proceedings of the Annual International Conference on Mobile Computing and Networking, MOBICOM | Year: 2011

Time-slotted, which means that primary users only change their status (active or not active) at the start of each secondary frame, has been considered as a common assumption in cognitive radio networks (CRNs). However, in realistic cases, primary users are non-time-slotted, which means primary users can be active or not active at any time during the whole secondary frame duration. In not-time-slotted CRNs, it is difficult to obtain good performance by using the traditional half duplex spectrum sensing scheme. In this paper, we propose a novel full duplex spectrum sensing scheme for non-time-slotted CRNs. We derive the probability of detection and the probability of false alarm with random arrival/departure of primary users' traffic and develop a continuous time Markov chain model for non-time-slotted CRNs. We analyze the effect of bandwidth, antennas placement error, and transmit signal amplitude difference on the performance of non-time-slotted CRNs. Numerical results show that the bandwidth, which is the most unavoidable imperfect factor, has little impact on performance of non-time-slotted CRNs. Therefore, the full duplex spectrum sensing scheme can be effectively used in wideband CRNs. © 2011 ACM.


Zhang L.,Xidian University | Qiao Z.-J.,University of Texas–Pan American | Xing M.-D.,Xidian University | Sheng J.-L.,Xidian University | And 2 more authors.
IEEE Transactions on Antennas and Propagation | Year: 2012

Compressive sensing (CS) theory indicates that the optimal reconstruction of an unknown sparse signal can be achieved from limited noisy measurements by solving a sparsity- driven optimization problem. For inverse synthetic aperture radar (ISAR) imagery, the scattering field of the target is usually composed of only a limited number of strong scattering centers, representing strong spatial sparsity. This paper derives a new autofocus algorithm to exploit the sparse apertures (SAs) data for ISAR imagery. A sparsity-driven optimization based on Bayesian compressive sensing (BCS) is developed. In addition, we also propose an approach to determine the sparsity coefficient in the optimization by using constant-false-alarm-rate (CFAR) detection. Solving the sparsity-driven optimization with a modified Quasi-Newton algorithm, the phase error is corrected by combining a two-step phase correction approach, and well-focused image with effective noise suppression is obtained from SA data. Real data experiments show the validity of the proposed method. © 2011 IEEE.


Cai N.,Chinese University of Hong Kong | Cai N.,Xidian University | Yeung R.W.,Chinese University of Hong Kong
IEEE Transactions on Information Theory | Year: 2011

In the paradigm of network coding, the nodes in a network are allowed to encode the information received from the input links. With network coding, the full capacity of the network can be utilized. In this paper, we propose a model, call the wiretap network, that incorporates information security with network coding. In this model, a collection of subsets of the channels in the network is given, and a wiretapper is allowed to access any one (but not more than one) of these subsets without being able to obtain any information about the message transmitted. Our model includes secret sharing in classical cryptography as a special case. We present a construction of secure linear network codes that can be used provided a certain graph-theoretic condition is satisfied. We also prove the necessity of this condition for the special case that the wiretapper may choose to access any subset of channels of a fixed size. The optimality of our code construction is established for this special case. Finally, we extend our results to the scenario when the wiretapper is allowed to obtain a controlled amount of information about the message. © 2006 IEEE.


Yang Y.,Xidian University | Li Q.,Chinese University of Hong Kong | Ma W.-K.,Chinese University of Hong Kong | Ge J.,Xidian University | Ching P.C.,Chinese University of Hong Kong
IEEE Signal Processing Letters | Year: 2013

This letter studies cooperative secure beamforming for amplify-and-forward (AF) relay networks in the presence of multiple eavesdroppers. Under both total and individual relay power constraints, we propose two schemes, namely secrecy rate maximization (SRM) beamforming and null-space beamforming. In the first scheme, our design problem is based on SRM. Using a suboptimal, but convex, techniquesemidefinite relaxation (SDR), we show that this problem can be handled by performing a one-dimensional search which involves solving a sequence of semidefinite programs (SDPs). To reduce the complexity, in the second scheme, we instead maximize the information rate at the destination while completely eliminating the information leakage to all eavesdroppers. We prove that this problem can be exactly solved by SDR with one SDP only. Simulation results demonstrate the performance gains of the two proposed designs. © 1994-2012 IEEE.


Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University | Da Costa D.B.,Federal University of Ceará | Jiang Z.,Xian Communication Institute
IEEE Transactions on Wireless Communications | Year: 2012

This Letter proposes a mechanism to combine multiuser diversity (MUD) and incremental relaying in a multiuser two-way relaying system, where one end-source exchanges messages with one out of N available end-sources by using a half-duplex amplify-and-forward (AF) relay. Outage analysis for the proposed scheme is carried out and, compared with the time division broadcast (TDBC) protocol, reveals that it not only realizes full diversity order (N+1) but also achieves improved expected spectral efficiency. Also, it is indicated that the expected spectral efficiency of the proposed scheme approaches that of the analog network coding (ANC) protocol in high signal-to-noise ratio (SNR) regime. Furthermore, the finite-SNR diversity-multiplexing tradeoff (DMT) is examined, from which the superiority of the proposed scheme to TDBC is confirmed as well. Other insightful comparisons in terms of the outage performance are presented that show the practical usefulness of our multiuser two-way relaying framework. © 2012 IEEE.


Lan J.,Guangxi University | Hu M.,Guangxi University | Ye X.,Guangxi University | Sun S.,Xidian University
Knowledge-Based Systems | Year: 2012

In this paper, relations between a multiplicative consistent interval fuzzy preference relation and an additive consistent interval fuzzy preference relation are established. Based on the new relations, a new method (Algorithm 3) is proposed to derive interval weights by transforming a multiplicative consistent interval fuzzy preference relation into an additive consistent interval fuzzy preference relation, collecting additive consistent information (Algorithm 2), transforming back into multiplicative consistent information and calculating the interval weights by Eq. (20). Finally, two numerical examples are given to illustrate the new method. © 2011 Elsevier B.V. All rights reserved.


Abbott P.,Brunel University | Zheng Y.,Royal Holloway, University of London | Du R.,Xidian University | Willcocks L.,The London School of Economics and Political Science
Journal of Strategic Information Systems | Year: 2013

In achieving success in global sourcing arrangements, the role of a cultural liaison, boundary spanner or transnational intermediary is frequently highlighted as being critical. This paper critiques, builds upon and synthesizes relevant streams of ideas in relation to boundary-spanning and cross-cultural management across a number of disciplines, and constructs a multi-layered creolization framework, encompassing processes at the individual, intra- and inter-organizational and inter-national levels which, we argue, are entangled and interrelated. Viewed as a vital and innovative phenomenon, creolization embodies the interactive, contentious and creative processes of network expansion, mutual sensemaking, cultural hybridity and identity multiplicity. Qualitative empirical data from the software and services outsourcing industry in Northwest China is used to demonstrate the complexity of cross-cultural practices in offshore collaborations and illustrate creolization processes. Potentials for theoretical development are outlined and implications for cross-cultural practices are discussed. © 2013 Elsevier B.V. All rights reserved.


Cheng W.,Texas A&M University | Zhang X.,Texas A&M University | Zhang H.,Xidian University
Proceedings - IEEE INFOCOM | Year: 2012

Integrating information theory with the principle of effective capacity, we propose the optimal resource allocation schemes for wireless full duplex and half duplex relay networks, respectively, to support the statistical quality-of-service (QoS) provisioning. In particular, we introduce a new control parameter, termed cancellation coefficient, to characterize the performance of full duplex relay transmission mode. For both amplitude-and-forward (AF) and decode-and-forward (DF) relay networks, we develop the dynamic hybrid resource allocation policies under full duplex and half duplex transmission modes to maximize the network throughput for the given delay QoS constraint measured by the QoS exponent. The numerical results obtained verify that our proposed resource allocation schemes can support diverse QoS requirements over wireless relay networks under full duplex and half duplex transmission modes. Our analysis indicates that the optimal effective capacity of perfect full duplex transmission mode is not the just twice as much as the optimal effective capacity of half duplex transmission mode. Our numerical analyses also show that the hybrid transmission mode can achieve better performance than just using full duplex or half duplex transmission mode alone. © 2012 IEEE.


Da Costa D.B.,Federal University of Ceará | Ding H.,Xidian University | Ding H.,Xian Communication Institute | Ge J.,Xidian University
IEEE Communications Letters | Year: 2011

In this letter, we investigate the outage performance of dual-hop decode-and-forward (DF) cooperative systems in an interference-limited Nakagami-m fading environment. More specifically, assuming the presence of Nakagami-m faded multiple co-channel interferers at the DF relay and a noisy destination, simple accurate closed-form approximations for the end-to-end outage probability are derived. To this end, moment-based estimators are used to attain the appropriate Nakagami-m fading parameters. Simulation results are presented in order to confirm the accuracy of the proposed approximations. © 2006 IEEE.


Li J.M.,Xidian University | Zhang G.,Luoyang Institute of Science and Technology
Iranian Journal of Fuzzy Systems | Year: 2012

This paper focuses on the non-fragile guaranteed cost control problem for a class of T-S fuzzy time-varying delay systems with local bilinear models. The objective is to design a non-fragile guaranteed cost state feedback controller via the parallel distributed compensation (PDC) approach such that the closed-loop system is delay-dependent asymptotically stable and the closed-loop performance is no more than a certain upper bound in the presence of the additive controller gain perturbations. A sufficient condition for the existence of such non-fragile guaranteed cost controllers is derived via the linear matrix inequality (LMI) approach and the design problem of the fuzzy controller is formulated in term of LMIs. The simulation examples show that the proposed approach is effective.


Zhang L.,Xidian University | Qiao Z.,University of Texas–Pan American | Xing M.-D.,Xidian University | Yang L.,Xidian University | Bao Z.,Xidian University
IEEE Transactions on Geoscience and Remote Sensing | Year: 2012

Unmanned aerial vehicle (UAV) synthetic aperture radar (SAR) is an essential tool for modern remote sensing applications. Owing to its size and weight constraints, UAV is very sensitive to atmospheric turbulence that causes serious trajectory deviations. In this paper, a novel databased motion compensation (MOCO) approach is proposed for the UAV SAR imagery. The approach is implemented by a three-step process: 1) The range-invariant motion error is estimated by the weighted phase gradient autofocus (WPGA), and the nonsystematic range cell migration function is calculated from the estimate for each subaperture SAR data; 2) the retrieval of the range-dependent phase error is executed by a local maximum-likelihood WPGA algorithm; and 3) the subaperture phase errors are coherently combined to perform the MOCO for the full-aperture data. Both simulated and real-data experiments show that the proposed approach is appropriate for highly precise imaging for UAV SAR equipped with only low-accuracy inertial navigation system. © 2012 IEEE.


Ning J.,Hong Kong Polytechnic University | Ning J.,Xidian University | Ning J.,Northwest University, China | Zhang L.,Hong Kong Polytechnic University | And 2 more authors.
Pattern Recognition | Year: 2010

Efficient and effective image segmentation is an important task in computer vision and object recognition. Since fully automatic image segmentation is usually very hard for natural images, interactive schemes with a few simple user inputs are good solutions. This paper presents a new region merging based interactive image segmentation method. The users only need to roughly indicate the location and region of the object and background by using strokes, which are called markers. A novel maximal-similarity based region merging mechanism is proposed to guide the merging process with the help of markers. A region R is merged with its adjacent region Q if Q has the highest similarity with Q among all Q's adjacent regions. The proposed method automatically merges the regions that are initially segmented by mean shift segmentation, and then effectively extracts the object contour by labeling all the non-marker regions as either background or object. The region merging process is adaptive to the image content and it does not need to set the similarity threshold in advance. Extensive experiments are performed and the results show that the proposed scheme can reliably extract the object contour from the complex background. © 2009 Elsevier Ltd. All rights reserved.


Wang Q.,Xidian University | Wang Q.,Northwest University, China | Yun Y.,Beijing Forestry University
Microchimica Acta | Year: 2012

We have investigated the oxidative electrochemistry of nitrite on glassy carbon electrodes modified with cobalt nanoparticles, poly(3,4-ethylenedioxythiophene) (PEDOT), and graphene. The modified electrode was characterized by cyclic voltammetry, electrochemical impedance spectroscopy, and scanning electron microscopy. The results suggest that this new type of electrode combines the advantages of PEDOT-graphene films and cobalt nanoparticles and exhibits excellent electrocatalytic activity towards the oxidation of nitrite. There is a linear relationship between the peak current and the nitrite concentration in the range from 0. 5 μM to 240 μM, and the detection limit is 0. 15 μM. The modified electrodes also enable the determination of nitrite at low potentials where the noise level and interferences by other electro-oxidizable compounds are weak. © 2012 Springer-Verlag.


Wang Q.,Northwest University, China | Wang Q.,Xidian University | Zheng J.,Northwest University, China | Zhang H.,Northwest University, China
Journal of Electroanalytical Chemistry | Year: 2012

A novel formaldehyde (HCHO) sensor fabricated by electrodeposition of AgPd alloy nanoparticles (NPs) on chitosan (Ch)-ionic liquid (IL, i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, OMIM·PF 6) films is developed. A scanning electron micrograph of the AgPd/Ch-IL composite film shows a uniform distribution of spherical AgPd NPs with particle sizes of 30-60 nm. Energy-dispersive X-ray measurements indicate that the mass ratio of Pd and Ag in the alloy is 21:5. Cyclic voltammetric studies show that an electrode coated with the AgPd/Ch-IL composite film exhibits high electrocatalytic activity and stability towards electrooxidation of HCHO. The HCHO sensor exhibits linear behavior in the concentration range from 0.060 mM to 20 mM, allowing quantitative analysis of HCHO with a detection limit of 0.022 mM (S/N = 3). © 2012 Elsevier B.V. All rights reserved.


Wei L.,Northwest University, China | Qi J.-J.,Xidian University
Knowledge-Based Systems | Year: 2010

One of the key problems of knowledge discovery is knowledge reduction. Rough set theory and the theory of concept lattices are two efficient tools for knowledge discovery. Attribute reduction based on rough set theory and the theory of concept lattices both have been researched. Since an information system, the data description of rough set theory, and a formal context, the data description of concept lattice theory, can be taken as the other one, the attribute reduction based on the same data base can be studied from these two perspectives, and researching their relation is significant. This paper mainly discusses the relation between concept lattice reduction and rough set reduction based on classical formal context, which will be meaningful for the relation research between these two theories, and for their knowledge discovery. © 2010 Elsevier B.V. All rights reserved.


Jia J.,Xidian University | Hu Q.,Fudan University
Computers and Industrial Engineering | Year: 2011

The paper studies the combined problem of pricing and ordering for a perishable product supply chain with one supplier and one retailer in a finite horizon. The lifetime of the product is two periods and demand in each period is random and price-sensitive. In each period, the supplier determines first a wholesale price and then the retailer decides an order quantity and retail prices. We show that the optimal pricing strategy for the non-fresh product depends only on its inventory, and the optimal pricing strategy and the optimal order quantity for the fresh product depend only on the wholesale price and they have a constant relation. Moreover, the game between the retailer and the supplier for finite horizon is equivalent to a one period game with only one order. Thus, the optimal policies are identical at each period. For the additive and multiplicative demands, we further obtain equations to compute the optimal strategies. All of above results are extended into the infinite horizon case and longer lifetime products. Finally, a numerical analysis is given. © 2010 Elsevier Ltd. All rights reserved.


Fang Y.,Northwest University, China | Wu J.,Xidian University | Huang B.,University of Wisconsin - Madison
Science China Information Sciences | Year: 2012

Recovery algorithms play a key role in compressive sampling (CS). Most of current CS recovery algorithms are originally designed for one-dimensional (1D) signal, while many practical signals are two-dimensional (2D). By utilizing 2D separable sampling, 2D signal recovery problem can be converted into 1D signal recovery problem so that ordinary 1D recovery algorithms, e. g. orthogonal matching pursuit (OMP), can be applied directly. However, even with 2D separable sampling, the memory usage and complexity at the decoder are still high. This paper develops a novel recovery algorithm called 2D-OMP, which is an extension of 1D-OMP. In the 2D-OMP, each atom in the dictionary is a matrix. At each iteration, the decoder projects the sample matrix onto 2D atoms to select the best matched atom, and then renews the weights for all the already selected atoms via the least squares. We show that 2D-OMP is in fact equivalent to 1D-OMP, but it reduces recovery complexity and memory usage significantly. What's more important, by utilizing the same methodology used in this paper, one can even obtain higher dimensional OMP (say 3D-OMP, etc.) with ease. © 2012 Science China Press and Springer-Verlag Berlin Heidelberg.


Ju H.,Xidian University | Liang B.,University of Toronto | Li J.,Xidian University | Yang X.,China Electronics Technology Group Corporation
IEEE Transactions on Wireless Communications | Year: 2013

A dynamic optimization algorithm is proposed for the joint allocation of subframes, resource blocks, and power in the Type 1 inband relaying scheme mandatory in the LTE-Advanced standard. Following the general framework of Lyapunov optimization, we decompose the original problem into three sub-problems in the forms of convex programming, linear programming, and mixed-integer programming.We solve the last sub-problem in the Lagrange dual domain, showing that it has zero duality gap, and that a primal optimum can be obtained with probability one. The proposed algorithm dynamically adapts to traffic and channel fluctuations, it accommodates both instantaneous and average power constraints, and it obtains arbitrarily near-optimal sum utility of each user's average throughput. Simulation results demonstrate that the joint optimum can significantly outperform suboptimal alternatives. © 2013 IEEE.


Zhang G.-Y.,Xidian University | Zhao W.-G.,China Aerospace Science and Technology Corporation
Tribology Letters | Year: 2014

The spiral groove face seal is a prime candidate for application of the liquid oxygen and liquid hydrogen turbopump. The study investigated the designs of the electro-magnetic loading device (EMLD) and friction torque testing device (FTTD), and their application in the interface experiments of face seals with spiral grooves which used water as the sealing fluid. The seal performance parameters, including face temperature, face friction torque, film pressure at the seal dam, were measured under the static balance position, and the effects of the face closing force, which varied with the axial load generated from the EMLD, on the seal performance were tested under a specific controlled mode. The result indicated that both the pressure at the seal dam and face temperature increased with the rotating speed and that small friction was obtained when the face seal was fully film-lubricated. The separation speed of the controllable seal could also be controlled, which helped seal faces lift off and met the conditions of the face noncontact status. Additionally, with the application of the EMLD and FTTD, seal operation monitoring was rendered possible and a controllable face seal with desirable performance was achieved. The findings of the current study lend great insights into engineering seal design and its applications. © Springer Science+Business Media New York 2014.


Ma W.,Xidian University | Sun S.,China Mobile
Designs, Codes, and Cryptography | Year: 2011

Frequency hopping sequences have been found wide applications in various modern frequency hopping spread spectrum communications and radar systems. With potential applications to these areas such as ultra wide bandwidth time hopping code division multiple access radio systems, multi-user and sonar systems, the design of quasi-synchronous time/frequency hopping code division multiple access systems by employing low hit zone hopping sequences has attracted wide attentions. In this paper, we present three construction methods for the low Hamming correlation zone frequency hopping sequences. The parameters of these sets of frequency hopping sequences with low hit zone are new and flexible. The constructed sequences are almost optimal and optimal respectively with respect to the Peng-Fan-Lee bounds. The simplicity of this technique makes it attractive for practical use. © 2010 Springer Science+Business Media, LLC.


Chen X.,U.S. National Institutes of Health | Chen X.,Xidian University | Bagci U.,U.S. National Institutes of Health
Medical Physics | Year: 2011

Purpose: This paper studies the feasibility of developing an automatic anatomy segmentation (AAS) system in clinical radiology and demonstrates its operation on clinical 3D images.Methods: The AAS system, the authors are developing consists of two main parts: object recognition and object delineation. As for recognition, a hierarchical 3D scale-based multiobject method is used for the multiobject recognition task, which incorporates intensity weighted ball-scale (b-scale) information into the active shape model (ASM). For object delineation, an iterative graph-cut-ASM (IGCASM) algorithm is proposed, which effectively combines the rich statistical shape information embodied in ASM with the globally optimal delineation capability of the GC method. The presented IGCASM algorithm is a 3D generalization of the 2D GC-ASM method that they proposed previously in Chen Proc. SPIE, 7259, 72590C1-72590C-8 (2009). The proposed methods are tested on two datasets comprised of images obtained from 20 patients (10 male and 10 female) of clinical abdominal CT scans, and 11 foot magnetic resonance imaging (MRI) scans. The test is for four organs (liver, left and right kidneys, and spleen) segmentation, five foot bones (calcaneus, tibia, cuboid, talus, and navicular). The recognition and delineation accuracies were evaluated separately. The recognition accuracy was evaluated in terms of translation, rotation, and scale (size) error. The delineation accuracy was evaluated in terms of true and false positive volume fractions (TPVF, FPVF). The efficiency of the delineation method was also evaluated on an Intel Pentium IV PC with a 3.4 GHZ CPU machine.Results: The recognition accuracies in terms of translation, rotation, and scale error over all organs are about 8 mm, 10° and 0.03, and over all foot bones are about 3.5709 mm, 0.35° and 0.025, respectively. The accuracy of delineation over all organs for all subjects as expressed in TPVF and FPVF is 93.01% and 0.22%, and all foot bones for all subjects are 93.75% and 0.28%, respectively. While the delineations for the four organs can be accomplished quite rapidly with average of 78 s, the delineations for the five foot bones can be accomplished with average of 70 s.Conclusions: The experimental results showed the feasibility and efficacy of the proposed automatic anatomy segmentation system: (a) the incorporation of shape priors into the GC framework is feasible in 3D as demonstrated previously for 2D images; (b) our results in 3D confirm the accuracy behavior observed in 2D. The hybrid strategy IGCASM seems to be more robust and accurate than ASM and GC individually; and (c) delineations within body regions and foot bones of clinical importance can be accomplished quite rapidly within 1.5 min. © 2011 American Association of Physicists in Medicine.


Jiang Z.-Y.,Xidian University | Ma J.-F.,Xidian University | Jing X.,Northwest University, China
Physica A: Statistical Mechanics and its Applications | Year: 2015

Based on the consideration of easy implementation of new routing strategies on many real complex networks such as the Internet, we propose a hybrid routing mechanism composed of the shortest path routing and the global dynamic routing strategy to improve the network traffic capacity. Under the background of current routing policy and network structure, packets can be sent along the shortest paths or by using source routing information. In this work, a global dynamic source routing strategy is employed as a supplementary routing mechanism to bypass central nodes and increase the delivery capacity utilization of all nodes significantly in the network. The traffic capacity of networked complex systems can be enhanced tens of times at the cost of a little average path lengthening. This hybrid routing method is very useful to network service providers and can be constitutionally supported on several networked complex systems such as the Internet and wireless ad hoc networks. © 2014 Elsevier B.V. All rights reserved.


Wang Q.,Northwest University, China | Wang Q.,Xidian University | Zheng J.,Northwest University, China
Microchimica Acta | Year: 2010

A strategy to fabricate a hydrogen peroxide (HP) sensor is developed by electrodepositing silver nanoparticles (Ag NPs) on a modified glassy carbon electrode (GCE) with a zinc oxide (ZnO) film. The Ag NPs/ZnO/GCE has been characterized by scanning electron microscopy, cyclic voltammetry, and chronoamperometry. It has been found that the Ag NPs synthesized in the presence of ZnO film provide an electrode with enhanced sensitivity and excellent stability. The sensitivity to HP is enhanced 3-fold by using Ag NPs/ZnO/GCE compared to Ag NPs/GCE. The HP sensor exhibits good linear behavior in the concentration range 2 μM to 5.5 mM for the quantitative analysis of HP with a detection limit of 0.42 μM (S/N = 3). © Springer-Verlag 2010.


Wang B.,Xidian University | Wang B.,University of Toronto | Li B.,University of Toronto | Li H.,Xidian University
Proceedings - IEEE INFOCOM | Year: 2013

With data services in the cloud, users can easily modify and share data as a group. To ensure data integrity can be audited publicly, users need to compute signatures on all the blocks in shared data. Different blocks are signed by different users due to data modifications performed by different users. For security reasons, once a user is revoked from the group, the blocks, which were previously signed by this revoked user must be re-signed by an existing user. The straightforward method, which allows an existing user to download the corresponding part of shared data and re-sign it during user revocation, is inefficient due to the large size of shared data in the cloud. In this paper, we propose a novel public auditing mechanism for the integrity of shared data with efficient user revocation in mind. By utilizing proxy re-signatures, we allow the cloud to re-sign blocks on behalf of existing users during user revocation, so that existing users do not need to download and re-sign blocks by themselves. In addition, a public verifier is always able to audit the integrity of shared data without retrieving the entire data from the cloud, even if some part of shared data has been re-signed by the cloud. Experimental results show that our mechanism can significantly improve the efficiency of user revocation. © 2013 IEEE.


Liu J.,Xidian University | Zhang Z.,Orange S.A. | Chen X.,Xidian University | Kwak K.S.,Inha University
IEEE Transactions on Parallel and Distributed Systems | Year: 2014

Wireless body area network (WBAN) has been recognized as one of the promising wireless sensor technologies for improving healthcare service, thanks to its capability of seamlessly and continuously exchanging medical information in real time. However, the lack of a clear in-depth defense line in such a new networking paradigm would make its potential users worry about the leakage of their private information, especially to those unauthenticated or even malicious adversaries. In this paper, we present a pair of efficient and light-weight authentication protocols to enable remote WBAN users to anonymously enjoy healthcare service. In particular, our authentication protocols are rooted with a novel certificateless signature (CLS) scheme, which is computational, efficient, and provably secure against existential forgery on adaptively chosen message attack in the random oracle model. Also, our designs ensure that application or service providers have no privilege to disclose the real identities of users. Even the network manager, which serves as private key generator in the authentication protocols, is prevented from impersonating legitimate users. The performance of our designs is evaluated through both theoretic analysis and experimental simulations, and the comparative studies demonstrate that they outperform the existing schemes in terms of better trade-off between desirable security properties and computational overhead, nicely meeting the needs of WBANs. © 1990-2012 IEEE.


Wang Q.,Xidian University | Wang Q.,Northwest University, China | Yun Y.,Beijing Forestry University
Microchimica Acta | Year: 2013

We have developed a nonenzymatic sensor for hydrogen peroxide (HP) that is based on a new kind of nanocomposite consisting of silver nanoparticles (AgNPs) electrodeposited on a basic film of a poly(ionic liquid) containing graphene. The nanocomposite was characterized by scanning electron microscopy, energy dispersive X-ray studies, cyclic voltammetry, and chronoamperometry. The AgNPs on the basic composite film provide the electrode with enhanced sensitivity in that the signal obtained for HP is 10-fold improved in the best case. The sensor exhibits good linear response in the 0. 1 μM to 2. 2 mM HP concentration range, and the detection limit is 0. 05 μM (at S/N = 3). © 2012 Springer-Verlag Wien.


Yang R.,Queen Mary, University of London | Yang R.,Xidian University | Tang W.,Queen Mary, University of London | Hao Y.,Queen Mary, University of London
Optics Express | Year: 2011

A zone plate lens utilizing a refractive instead of diffractive approach is presented for broadband operation. By utilizing transformation optics, we compress the conventional hyperbolic lens into a flat one with a few zone plates made of all-dielectric materials. Such a transformed lens maintains the broadband performance of the original lens, thus providing a superior alternative to the diffractive Fresnel element which is inherently narrow band. © 2011 Optical Society of America.


Ma J.,Xidian University | Ma J.,Leibniz University of Hanover | Temizer I.,Leibniz University of Hanover | Wriggers P.,Leibniz University of Hanover
International Journal of Solids and Structures | Year: 2011

In this work, random homogenization analysis of heterogeneous materials is addressed in the context of elasticity, where the randomness and correlation of components' properties are fully considered and random effective properties together with their correlation for the two-phase heterogeneous material are then sought. Based on the analytical results of homogenization in linear elasticity, when the randomness of bulk and shear moduli, the volume fraction of each constituent material and correlation among random variables are considered simultaneously, formulas of random mean values and mean square deviations of analytical bounds and estimates are derived from Random Factor Method. Results from the Random Factor Method and the Monte-Carlo Method are compared with each other through numerical examples, and impacts of randomness and correlation of random variables on the random homogenization results are inspected by two methods. Moreover, the correlation coefficients of random effective properties are obtained by the Monte-Carlo Method. The Random Factor Method is found to deliver rapid results with comparable accuracy to the Monte-Carlo approach. © 2010 Elsevier Ltd. All rights reserved.


Yang R.,Xidian University | Lei Z.,Xidian University | Chen L.,Xidian University | Wang Z.,Xidian University | Hao Y.,Queen Mary, University of London
IEEE Transactions on Antennas and Propagation | Year: 2014

A new class of dielectric sheet antennas is presented based on transformation optics. Specifically, we successfully implement the transformation with a consideration of surface wave eigenmode properties, and carry out a practical perforated design by drilling holes to synthesize the required dielectric constants for their potential realization. The full wave simulation shows that our surface wave transformation lens antenna is capable of obtaining a greatly improved directivity, while maintaining the original low profile. © 1963-2012 IEEE.


Zhao F.,University of Posts and Telecommunications | Liu H.,Shanxi Normal University | Jiao L.,Xidian University
Digital Signal Processing: A Review Journal | Year: 2011

Spectral clustering algorithms have been successfully used in the field of pattern recognition and computer vision. The widely used similarity measure for spectral clustering is Gaussian kernel function which measures the similarity between data points. However, it is difficult for spectral clustering to choose the suitable scaling parameter in Gaussian kernel similarity measure. In this paper, utilizing the prototypes and partition matrix obtained by fuzzy c-means clustering algorithm, we develop a fuzzy similarity measure for spectral clustering (FSSC). Furthermore, we introduce the K-nearest neighbor sparse strategy into FSSC and apply the sparse FSSC to texture image segmentation. In our experiments, we firstly perform some experiments on artificial data to verify the efficiency of the proposed fuzzy similarity measure. Then we analyze the parameters sensitivity of our method. Finally, we take self-tuning spectral clustering and Nyström methods for baseline comparisons, and apply these three methods to the synthetic texture and remote sensing image segmentation. The experimental results show that the proposed method is significantly effective and stable. © 2011 Elsevier Inc. All rights reserved.


Liu D.,Xidian University | Li Z.,Xidian University | Zhou M.,Tongji University | Zhou M.,New Jersey Institute of Technology
Automatica | Year: 2013

The work proposes a synthesis method of supervisors for flexible manufacturing systems modeled by a class of generalized Petri nets. A concept of resource usage ratios (RU-ratios) is first presented to describe the occupation degree of a resource by an operation. Next, an intrinsically live structure characterized by a special numerical relationship between arc-weights and initial markings is investigated from a perspective of RU-ratios. Then, a new kind of supervisors is synthesized on the ground of the generic nature of the intrinsically live structure. Such a supervisor can achieve the purposes of both liveness-enforcement and resource usage ratio-enforcement of the system under consideration. Given a plant, it is easy to determine the topological structure of such a supervisor and the number of monitors is bounded by that of resources used in the plant. In addition, when the configuration of the plant model changes, the supervisor can be reusable through adjusting control parameters only without rearrangement of connections. This makes it easy enough and intuitive to be used by industrial practitioners. Instead of maximal behavioral permissiveness, it pursues a precise usage of shared resources that are limited and valuable. Several examples are used to illustrate the proposed methods. © 2013 Elsevier Ltd. All rights reserved.


Ming Z.,Xidian University | Zhou M.,Tongji University | Zhou M.,New Jersey Institute of Technology
IEEE Transactions on Industrial Electronics | Year: 2011

Motivated by the method to analyze the impact of dead time in hard-switching converters, this paper, for the first time, analyzes the impact of zero-voltage notches on the outputs of soft-switching pulsewidth modulation (PWM) converters. It proves that the output distortion of soft-switching converters due to their deviation voltage is independent of the direction of their output current. Hence, their compensation strategies require no sensor to detect the current's direction, which is required by dead-time compensation methods in hard-switching converters. A simple yet effective compensation algorithm is presented for soft-switching converters. The analysis result and effectiveness of the proposed algorithm are experimentally verified via a three-phase inverter that represents an important class of converters. © 2010 IEEE.


Shang F.,Xidian University | Liu Y.,Xidian University | Wang F.,IBM
Proceedings - IEEE International Conference on Data Mining, ICDM | Year: 2011

In recent years, semi-supervised clustering (SSC) has aroused considerable interests from the machine learning and data mining communities. In this paper, we propose a novel semi-supervised clustering approach with enhanced spectral embedding (ESE) which not only considers structure information contained in data sets but also makes use of prior side information such as pairwise constraints. Specially, we first construct a symmetry-favored k-NN graph which is highly robust to noisy objects and can reflect the underlying manifold structure of data. Then we learn the enhanced spectral embedding towards an ideal representation as consistent with the pairwise constraints as possible. Finally, through taking advantage of Laplacian regularization, we formulate learning spectral representation as semidefinite-quadratic-linear programs (SQLPs) under the squared loss function or small semidefinitive programs (SDPs) under the hinge loss function, which both can be efficiently solved. Experimental results on a variety of synthetic and real-world data sets show that our approach outperforms the state-of-the-art SSC algorithms on both vector-based and graph-based clustering. © 2011 IEEE.


Yan Z.,Xidian University | Yan Z.,Aalto University | Prehofer C.,Fraunhofer Institute for Communication Systems
IEEE Transactions on Dependable and Secure Computing | Year: 2011

Trust plays an important role in software systems, especially component-based systems in which components or their environments vary. This paper introduces an autonomic trust management solution for a component-based software system. We propose an adaptive trust control model to specify, evaluate, establish, and ensure the trust relationships among system entities. This model concerns the quality attributes of the entity and a number of trust control modes supported by the system. In particular, its parameters can be adaptively adjusted based on runtime trust assessment in order to reflect real system context and situation. Based on this model, we further develop a number of algorithms that can be adopted by a trust management framework for autonomic management of trust during component execution. We verify the algorithms' feasibility through simulations and demonstrate the effectiveness and benefits of our solution. We also discuss the issues for successful deployment of our solution in a component software platform. © 2011 IEEE.


Xiao B.,Xidian University | Xiao B.,Ningxia University | Ma J.-F.,Xidian University | Cui J.-T.,Xidian University
Pattern Recognition | Year: 2012

The idea of scale and rotation invariant image recognition based on Radon and FourierMellin transforms has been presented recently. In this paper, we extend the previous work and propose a new method to construct a set of combined blur, translation, scale and rotation invariants using Radon and pseudo-FourierMellin transforms, named Radon and pseudo-FourierMellin invariants (RPFMI). The proposed method is robust to additive white noise as a result of summing pixel values to generate projections in the Radon transform step. We also present a mathematical framework of obtaining the Radon and pseudo-FourierMellin transforms of blurred images, and a framework of deriving the combined blur, scale and rotation invariants. Theoretical and experimental results show the superiority of the proposed method and its robustness to additive white noise in comparison with some recent methods. © 2011 Elsevier Ltd. All rights reserved.


Shang F.,Xidian University | Jiao L.C.,Xidian University | Shi J.,Xidian University | Wang F.,IBM | Gong M.,Xidian University
Pattern Recognition | Year: 2012

In this paper, we propose a novel Fast Affinity Propagation clustering approach (FAP). FAP simultaneously considers both local and global structure information contained in datasets, and is a high-quality multilevel graph partitioning method that can implement both vector-based and graph-based clustering. First, a new Fast Sampling algorithm (FS) is proposed to coarsen the input sparse graph and choose a small number of final representative exemplars. Then a density-weighted spectral clustering method is presented to partition those exemplars on the global underlying structure of data manifold. Finally, the cluster assignments of all data points can be achieved through their corresponding representative exemplars. Experimental results on two synthetic datasets and many real-world datasets show that our algorithm outperforms the state-of-the-art original affinity propagation and spectral clustering algorithms in terms of speed, memory usage, and quality on both vector-based and graph-based clustering. © 2011 Elsevier Ltd. All rights reserved.


Zhang L.,Soochow University of China | Zhang L.,Xidian University | Zhou W.-D.,Soochow University of China
Pattern Recognition | Year: 2011

This paper proposes a new classifier called density-induced margin support vector machines (DMSVMs). DMSVMs belong to a family of SVM-like classifiers. Thus, DMSVMs inherit good properties from support vector machines (SVMs), e.g., unique and global solution, and sparse representation for the decision function. For a given data set, DMSVMs require to extract relative density degrees for all training data points. These density degrees can be taken as relative margins of corresponding training data points. Moreover, we propose a method for estimating relative density degrees by using the K nearest neighbor method. We also show the upper bound on the leave-out-one error of DMSVMs for a binary classification problem and prove it. Promising results are obtained on toy as well as real-world data sets. © 2011 Elsevier Ltd. All rights reserved.


Song X.-F.,Xidian University | Song X.-F.,Henan University | Jiao L.-C.,Xidian University
Dianzi Yu Xinxi Xuebao/Journal of Electronics and Information Technology | Year: 2012

This paper presents a novel classification algorithm of hyperspectral remote sensing image based on sparse representation and spectral information. First, a learning dictionary is obtained based on hyperspectral remote sensing image data set, and then the sparse coefficient of each pixel is calculated according to the learni