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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.

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.

Bai X.,Xidian University | Bai X.,Northwest Normal University
Electronics Letters | Year: 2012

A space-alignment scheme based on primary transmission-outage (TO) for cognitive transmission in a multiple-input multiple-output uplink system is proposed. The main idea is that a secondary transmitter aligns its transmit directions by precoding to unused primary channel eigenmodes where the TO event happened, which is denoted by bit error rate (BER) over a target BER which is the typical minimum value required for acceptable system performance. The proposed scheme achieves a higher performance in comparison with the SA scheme of zero outage. © 2012 The Institution of Engineering and Technology.

Peng X.,Arizona State University | Wei Q.,Arizona State University | Wei Q.,Xidian University | Copple A.,Arizona State University
Physical Review B - Condensed Matter and Materials Physics | Year: 2014

Recently fabricated two-dimensional phosphorene crystal structures have demonstrated great potential in applications of electronics. In this paper, strain effect on the electronic band structure of phosphorene was studied using first-principles methods including density functional theory (DFT) and hybrid functionals. It was found that phosphorene can withstand a tensile stress and strain up to 10 N/m and 30%, respectively. The band gap of phosphorene experiences a direct-indirect-direct transition when axial strain is applied. A moderate -2% compression in the zigzag direction can trigger this gap transition. With sufficient expansion (+11.3%) or compression (-10.2% strains), the gap can be tuned from indirect to direct again. Five strain zones with distinct electronic band structure were identified, and the critical strains for the zone boundaries were determined. Although the DFT method is known to underestimate band gap of semiconductors, it was proven to correctly predict the strain effect on the electronic properties with validation from a hybrid functional method in this work. The origin of the gap transition was revealed, and a general mechanism was developed to explain energy shifts with strain according to the bond nature of near-band-edge electronic orbitals. Effective masses of carriers in the armchair direction are an order of magnitude smaller than that of the zigzag axis, indicating that the armchair direction is favored for carrier transport. In addition, the effective masses can be dramatically tuned by strain, in which its sharp jump/drop occurs at the zone boundaries of the direct-indirect gap transition. © 2014 American Physical Society.

Deadlocks are a highly undesired situation in a fully automated flexible manufacturing system, whose occurrences are tied to the existence of shared resources that are competed by different production processes. In the last two decades, a fair amount of research has been done on deadlock analysis and control for flexible manufacturing systems, leading to a variety of strategies in the literature. Petri nets are a promising mathematical tool to handle deadlock problems in flexible manufacturing systems. However, most deadlock control policies based on a Petri net formalism assume that all the transitions in a plant model are controllable. However, uncontrollability of events are a natural feature in a real-world production system. This paper proposes a deadlock prevention policy for a class of Petri nets by considering the existence of uncontrollable transitions. Deadlocks are prevented by adding monitors to a plant Petri net model, whose addition does not inhibit the firings of uncontrollable transitions. Linear programming techniques are employed to find transitions to which a monitor points in order that a more permissive liveness-enforcing Petri net supervisor can be found. A number of manufacturing examples are used to demonstrate the proposed methods. Copyright © 2011 John Wiley and Sons Asia Pte Ltd.

Peng X.,Arizona State University | Copple A.,Arizona State University | Wei Q.,Arizona State University | Wei Q.,Xidian University
Journal of Applied Physics | Year: 2014

Two dimensional few-layer black phosphorus crystal structures have recently been fabricated and have demonstrated great potential in electronic applications. In this work, we employed first principles density functional theory calculations to study the edge and quantum confinement effects on the electronic properties of the phosphorene nanoribbons (PNR). Different edge functionalization groups, such as H, F, Cl, OH, O, S, and Se, in addition to a pristine case were studied for a series of ribbon widths up to 3.5nm. It was found that the armchair-PNRs (APNRs) are semiconductors for all edge groups considered in this work. However, the zigzag-PNRs (ZPNRs) show either semiconductor or metallic behavior in dependence on their edge chemical species. Family 1 edges (i.e., H, F, Cl, OH) form saturated bonds with P atoms in the APNRs and ZPNRs, and the edge states keep far away from the band gap. However, Family 2 edges (pristine, O, S, Se) form weak unsaturated bonds with the pz orbital of the phosphorus atoms and bring edge states within the band gap of the ribbons. For the ZPNRs, the edge states of Family 2 are present around the Fermi level within the band gap, which close up the band gap of the ZPNRs. For the APNRs, these edge states are located at the bottom of the conduction band and result in a reduced band gap. © 2014 AIP Publishing LLC.

Li G.Y.,Georgia Institute of Technology | Niu J.,Xidian University | Lee D.,Georgia Institute of Technology | Fan J.,Xian 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.

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.

Wang H.,Dalian Ocean University | Wang H.,Xidian University | Zhang Y.,University of Chinese Academy of Sciences
IEEE Transactions on Parallel and Distributed Systems | Year: 2014

Provable data possession (PDP) is a probabilistic proof technique for cloud service providers (CSPs) to prove the clients' data integrity without downloading the whole data. In 2012, Zhu et al. proposed the construction of an efficient PDP scheme for multicloud storage. They studied the existence of multiple CSPs to cooperatively store and maintain the clients' data. Then, based on homomorphic verifiable response and hash index hierarchy, they presented a cooperative PDP (CPDP) scheme from the bilinear pairings. They claimed that their scheme satisfied the security property of knowledge soundness. It is regretful that this comment shows that any malicious CSP or the malicious organizer (O) can generate the valid response which can pass the verification even if they have deleted all the stored data, i.e., Zhu et al.'s CPDP scheme cannot satisfy the property of knowledge soundness. Then, we discuss the origin and severity of the security flaws. It implies that the attacker can get the pay without storing the clients' data. It is important to clarify the scientific fact to design more secure and practical CPDP scheme in Zhu et al.'s system architecture and security model. © 2014 IEEE.

Single-layer graphdiyne was proposed as substrate for single-atom Sc and Ti catalysts with much larger binding energy and higher thermal migration barrier than graphene. By density functional theory calculations, the electronic properties, thermal stabilities and catalytic abilities of Sc and Ti adatoms on single-layer graphdiyne were theoretically investigated. The results indicate that the C sites on graphdiyne surface are the most stable binding sites for Sc and Ti adatoms. The high migration barrier prevents the aggregation of Sc and Ti adatoms on graphdiyne surface. On graphdiyne-Sc or graphdiyne-Ti, CO could be catalytically oxidated by a four-step reaction. The reaction is both energetically and kinetically favorable with low potential barriers. Overall, Sc and Ti adatoms on single-layer graphdiyne would be excellent catalysts for CO oxidation. © 2016 Elsevier Ltd

Guo H.,Xidian University | Xie Q.-Y.,Lanzhou University | Fu C.-E.,Xian 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 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.

Wang L.,Xidian University | Guan B.-R.,Hangzhou Dianzi University
Journal of Electromagnetic Waves and Applications | Year: 2012

A novel high selectivity dual-band band-pass filter (BPF) is presented in this article. This BPF incorporates two sets of resonators: two one-wavelength microstrip line resonators with one end short-circuited on the top layer for generating the second passband and a dual-mode defected ground structure resonator (DDGSR) on the bottom layer for generating the first passband. The two microstrip line resonators are used not only as resonant elements, but also as a part of the feed structures with inductive source-load coupling for exciting the DDGSR. Using the intrinsic characteristics of the resonators and feed structures, multiple transmission zeros located at both sides of the first passband can be realized to achieve high selectivity. An experimental dual-band BPF located at 2.4/4 GHz has been simulated and fabricated. This design method is verified by good agreement between the simulated and measured results. © 2012 Taylor & Francis.

Mu M.,Virginia Polytechnic Institute and State University | Zheng F.,Xidian University | Li Q.,Virginia Polytechnic Institute and State University | Lee F.C.,Virginia Polytechnic Institute and State University
IEEE Transactions on Power Electronics | Year: 2013

Finite element analysis is a popular way to analyze magnetic core loss in complex core structures. However, accurate calculation of the inductor core loss under dc bias conditions is still a challenge, as magnetic properties such as permeability and core-loss density change when a dc premagnetization is present, especially for saturable cores. This paper proposes a method that can accurately calculate the inductor's loss when it works under dc bias current conditions. The method utilizes an effective and simple material model built by curve-fitting the measurement data. To prove the accuracy of this approach, planar inductors built with low-temperature co-fired ceramic ferrite are simulated, and the calculated core losses are experimentally verified. © 2012 IEEE.

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.

Chen G.,Huizhou University | Yang Y.,Huizhou University | Li J.,Xidian University
IET Control Theory and Applications | Year: 2012

This note considers the finite time stability of a class of hybrid dynamical systems, which has both switching and impulsive effect. First, by relaxing the restriction on Lyapunov function of the system, a new condition of finite time stability is given for non-linear systems. Then, this condition and the results of previous works (Bhat and Bernstein, 2000; Moulay and Perruquetti, 2003) are extended to study the finite time stability of a class of hybrid dynamical systems, several sufficient conditions are derived. Finally, a numerical example is given to illustrate the theoretical results. © 2011 The Institution of Engineering and Technology.

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.

Ning W.,Xidian University
Information Processing Letters | Year: 2016

Li et al. proposed a new interconnection network, named exchanged crossed cube ECQ(s,t), which has better properties than other variations of hypercube in the field of the fewer diameter, smaller links and lower cost factor. This work will show that its super connectivity and super edge-connectivity are both equal to 2s with s≤t. It means that at least 2s vertices (resp. 2s edges) of ECQ(s,t) are moved away to obtain a disconnected graph avoiding isolated vertex. © 2015 Elsevier B.V.

For a multiple input channel, one may define different capacity regions, according to the criterions of error, types of codes, and presence of feedback. In this paper, we aim to draw a complete picture of relations among these different capacity regions. To this end, we first prove that the average-error-probability capacity region of a multiple input channel can be achieved by a random code under the criterion of maximum error probability. Moreover, we show that for a non-deterministic multiple input channel with feedback, the capacity regions are the same under two different error criterions. In addition, we discuss two special classes of channels to shed light on the relation of different capacity regions. In particular, to illustrate the roles of feedback, we provide a class of MAC, for which feedback may enlarge maximum-error-probability capacity regions, but not average-error-capacity regions. Besides, we present a class of MAC, as an example for which the maximum-error-probability capacity regions are strictly smaller than the average-error-probability capacity regions (first example showing this was due to G. Dueck). Differently from G. Dueck's enlightening example in which a deterministic MAC was considered, our example includes and further generalizes G. Dueck's example by taking both deterministic and non-deterministic MACs into account. Finally, we extend our results for a discrete memoryless two-input channel, to compound, arbitrarily varying MAC, and MAC with more than two inputs. © 2014 by the authors.

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.

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.

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.

Feng X.,Xidian University | Elden L.,Linkoping 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.

Liu G.,Xidian University | Chao D.Y.,National Chengchi University | Uzam M.,Meliksah University
International Journal of Production Research | Year: 2013

Recently, researchers have proposed a novel and computationally efficient method to design optimal control places and an iteration approach that computes the reachability graph once to obtain a maximally permissive, if any, liveness-enforcing supervisor of flexible manufacturing systems (FMS). The approach solves the set of integer linear inequalities to compute control places. If, given a Petri net model, no solution exists, the optimal control place does not exist for the Petri net model. We discover that a solution always exists for systems of simple sequential processes with resources (S 3PR), but not for the case of FMS modelled by generalised Petri nets (GPN). We propose a theory to prove that there are no good states that will be forbidden by the control policy for S3PR, in which live and dead states cannot have the same weighted sum of tokens in the complimentary set of a siphon. For a system of simple sequential processes with general resource requirements (S3PGR2) modelled by GPN, we find the reason why the integer linear programming (ILP) may not have solutions, which is consistent with the fact that optimal supervisor synthesis for GPN remains unknown. We show that live and dead states may have the same weighted sum of tokens in the complimentary set of a siphon in a GPN. These theoretical results are verified by case studies. © 2013 Taylor and Francis Group, LLC.

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.

Tuo S.,Shaanxi University of Technology | Yong L.,Shaanxi University of Technology | Yong L.,Xidian University
Journal of Computational Information Systems | Year: 2012

Harmony Search (HS) method is an emerging meta-heuristic optimization algorithm, which has been developed rapidly and has been applied widely during the past decade. In this paper, an improved harmony search with chaos (HSCH) is presented. The simulation results in solving benchmark problems demonstrate that the HSCH algorithm is valid and outperforms the classical HS algorithm and HS algorithm with differential mutation operator (HSDE). © 2011 by Binary Information Press.

Zhang M.,Baoji University of Arts And Sciences | Yan H.,Baoji University of Arts And Sciences | Wei Q.,Xidian University | Wang H.,Jilin University
Computational Materials Science | Year: 2013

Using particle swarm optimization technique on crystal structural prediction, a universal hexagonal MoB4-type structure was uncovered for WB4, TcB4, and ReB4. This MoB 4-type structure is energetically much superior to the previously proposed WB4-type structure and stable against decomposition into the mixture of TM and B at ambient conditions. The Young's modulus and shear modulus as a function of crystal orientation for the TMB4 (TM =W, Tc, and Re) have thus been systematically investigated. TMB4 within this hexagonal structure are found to be ultra-incompressible and hard due to their high bulk modulus and large hardness. Especially, they exhibit an unusual incompressibility along the c axis, close to that of diamond. Their ultra-incompressibility is attributed to a staking of B-TM-B "sandwiches" layers linked by strong covalent TM-B bonding, which is manifested by the PDOS and ELF analysis. © 2012 Elsevier B.V. All rights reserved.

Zhu Q.,Xidian University | Guo G.,West Virginia University | Wang D.,Montclair State University
IEEE Transactions on Computers | Year: 2014

An interconnection network's diagnosability is an important measure of its self-diagnostic capability. Based on the classical notion of diagnosability, strong diagnosability and conditional diagnosability were proposed later to better reflect the networks' self-diagnostic capability under more realistic assumptions. In this paper, we study a class of interconnection networks called strong networks, which are n -regular, (n - 1) -connected, and with cn -number no more than n - 3. We build a relationship among the three diagnosability measures for strong networks. Under both PMC and MM* models, given a strong network G with diagnosability t , we prove that G is strongly t -diagnosable if and only if G 's conditional diagnosability is greater than t. A simple check can show that almost all well-known regular interconnection networks are strong networks. The significance of this paper's result is that it reveals an important relationship between strong and conditional diagnosabilities, and the proof of strong diagnosability for many interconnection networks under MM* or PMC model is not necessary if their conditional diagnosability can be shown to be strictly larger than their diagnosability. © 2014 IEEE.

Zhu X.,Queensland University of Technology | Huang Z.,Queensland University of Technology | Cheng H.,Chinese University of Hong Kong | Cui J.,Xidian University | Shen H.T.,Queensland University of Technology
ACM Transactions on Information Systems | Year: 2013

Hash-based methods achieve fast similarity search by representing high-dimensional data with compact binary codes. However, both generating binary codes and encoding unseen data effectively and efficiently remain very challenging tasks. In this article, we focus on these tasks to implement approximate similarity search by proposing a novel hash based method named sparse hashing (SH for short). To generate interpretable (or semantically meaningful) binary codes, the proposed SH first converts original data into low-dimensional data through a novel nonnegative sparse coding method. SH then converts the low-dimensional data into Hamming space (i.e., binary encoding low-dimensional data) by a new binarization rule. After this, training data are represented by generated binary codes. To efficiently and effectively encode unseen data, SH learns hash functions by taking a-priori knowledge into account, such as implicit group effect of the features in training data, and the correlations between original space and the learned Hamming space. SH is able to perform fast approximate similarity search by efficient bit XOR operations in the memory of a modern PC with short binary code representations. Experimental results show that the proposed SH significantly outperforms state-of-the-art techniques. © 2013 ACM.

Li M.,PLA University of Science and Technology | Li M.,Engineering Co. | 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.

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.

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 T.,Xidian University
Aerospace Science and Technology | Year: 2012

A deployable space antenna has a deployment mechanism which has high precision and reliability. The articulated mechanism is able to alter its configuration without failure from a compact to deployed shape to meet specific operational requirements. Consequently, the analysis of the dynamic characteristic of the deployment mechanism must be done at an initial design stage. In this paper, the kinematic, dynamic analysis and control methods to predict the deployment motions of the hoop truss deployable antenna are presented. First, the general model of deployment kinematic analysis is established. The model can be applied to carrying out the position, velocity and acceleration analysis of any point on the structure. Second, the dynamic model for the hoop truss deployable antenna is established based on the Lagrange method in multibody dynamic systems and using absolute generalized coordinates, which takes into consideration the dissipative force, torques of torsional springs in hinges and the pretension forces in nets. The force-controlled method is presented to control the deployment motion, and the relation between the driving force and the deployment motion is derived. The variation of the driving force is obtained according to the planned deployment motion. The deployment dynamics of the hoop truss deployable antenna is simulated, and the effects of initial velocity, damping and gravity upon deployment are summarized. Deployment dynamic analysis and control of the hoop truss deployable antenna are carried out taking into account the stiffness of torsional spring, damping in joints, gravity and the pretension forces in nets. The results of simulation experiment validated the proposed method. © 2011 Elsevier Masson SAS. All rights reserved.

Zhang K.,Hubei Engineering University | Gao X.,Xidian University | Tao D.,Intelligent Systems Technology, Inc. | Li X.,CAS Xian Institute of Optics and Precision Mechanic
IEEE Transactions on Neural Networks and Learning Systems | Year: 2013

Example learning-based image super-resolution (SR) is recognized as an effective way to produce a high-resolution (HR) image with the help of an external training set. The effectiveness of learning-based SR methods, however, depends highly upon the consistency between the supporting training set and low-resolution (LR) images to be handled. To reduce the adverse effect brought by incompatible high-frequency details in the training set, we propose a single image SR approach by learning multiscale self-similarities from an LR image itself. The proposed SR approach is based upon an observation that small patches in natural images tend to redundantly repeat themselves many times both within the same scale and across different scales. To synthesize the missing details, we establish the HR-LR patch pairs using the initial LR input and its down-sampled version to capture the similarities across different scales and utilize the neighbor embedding algorithm to estimate the relationship between the LR and HR image pairs. To fully exploit the similarities across various scales inside the input LR image, we accumulate the previous resultant images as training examples for the subsequent reconstruction processes and adopt a gradual magnification scheme to upscale the LR input to the desired size step by step. In addition, to preserve sharper edges and suppress aliasing artifacts, we further apply the nonlocal means method to learn the similarity within the same scale and formulate a nonlocal prior regularization term to well pose SR estimation under a reconstruction-based SR framework. Experimental results demonstrate that the proposed method can produce compelling SR recovery both quantitatively and perceptually in comparison with other state-of-the-art baselines. © 2013 IEEE.

The aim of the multi-channel sampling expansion (MSE) is the reconstruction of an unknown continuously defined function ft, from the samples of the responses of m linear time invariant (LTI) systems, each sampled by the 1/m th Nyquist rate. The MSE for band-pass signals in the Fourier transform (FT) domain has recently been presented in the literature under some restricted conditions. To be specific, a necessary condition for perfect reconstruction of a band-pass signals is discussed which requires the number of filters/channels m in the system must be even. Focusing on this issue, first, based on a quadrature representation of the band-pass signal, we propose a new MSE. It is shown that perfect signal reconstruction is possible for any arbitrary number of channels when the upper cutoff frequency is a multiple of the bandwidth. Then, in order to show the importance of the MSE scheme, we apply the recurrent non-uniform sampling scheme to analyze high-rate waveform digitizers. The parallel architecture utilizes the interleaving/multiplexing techniques to extend the capabilities of the monolithic analog/digital (A/D) converter technology. Last, the MSE of band-pass signal is improved which can allow multiple sampling rates in the system. © 2016 Elsevier GmbH.

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.

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.

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.

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.

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 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.

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.

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.

Li N.,Xidian University
IET Microwaves, Antennas and Propagation | Year: 2016

This paper investigates effect of radiation surface error on the electrical properties of waveguide slotted arrays. For the waveguide slotted arrays working in Ku band, the radiation surface error caused by exterior loads and processing contains three components in different scales. Power spectrum conversion and Gaussian filtering are applied to error components separation, and three kinds of statistical models are introduced for error modelling. The multi-scale error model is obtained by weighted stacking. Based on the error model, effective mechanism formulations are developed with errors through the analysis of the positional difference of radiating slots in the aperture field. As a method of verification, an antenna prototype is manufactured and tested. A novel simulation method is proposed, which is tested by a contrast experiment on radiating surface's flatness. A comparison between results of the multi-scale error model and test data to the ideal case indicates that the proposed error model is closer to the test data. Influence degrees of all error components in different scales are compared and discussed. Reducing the error in the manufacturing process is an effective way to make sure the design accuracy of arrays, reduce production costs and shorten production cycles. © The Institution of Engineering and Technology.

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.

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.

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.

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.

Lin Z.-Z.,Xidian University | Chen X.,Xian 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.

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.

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.

Zhao M.,Shihezi University | Hou Y.,Xidian University
Discrete Event Dynamic Systems: Theory and Applications | Year: 2013

This paper presents a novel and computational deadlock prevention policy for a class of generalized Petri nets, namely G-systems, which allows multiple resource acquisitions and flexible routings with machining, assembly and disassembly operations. In this research, a mixed integer programming (MIP)-based deadlock detection technique is used to find an insufficiently marked minimal siphon from a maximal deadly marked siphon for generalized Petri nets. In addition, two-stage control method is employed for deadlock prevention in Petri net model. Such proposed method is an iterative approach consisting of two stages. The first one is called siphons control, which adds a control place to the original net for each insufficiently marked minimal siphon. The objective is to prevent minimal siphons from being insufficiently marked. The second one, called control-induced siphons control, is to add a control place to the augmented net with its output arcs connecting to source transitions, which assures that there is no new insufficiently marked siphon generated due to the addition of the monitors. Compared with the existing approaches, the proposed deadlock prevention policy can usually lead to a non-blocking supervisor with more permissive behavior and high computational efficiency for a sizeable plant model due to avoiding complete siphon enumeration. Finally, a practical flexible manufacturing system (FMS) example is utilized to illustrate the proposed method. © 2011 Springer Science+Business Media, LLC.

Yang Y.-R.,Lanzhou Jiaotong University | Li W.-T.,Lanzhou University | Wu S.-L.,Xidian University
Nonlinear Analysis: Real World Applications | Year: 2013

This paper is concerned with traveling waves of a monostable reaction-diffusion system with delay and without quasi-monotonicity. When the initial perturbation around the traveling wave is suitably small in a weighted norm, the exponential stability of all traveling wave solutions for the system with delay is proved by the weighted energy method. © 2012 Elsevier Ltd. All rights reserved.

Bai Z.,Xidian University
Mathematical Methods in the Applied Sciences | Year: 2015

This paper is devoted to the investigation of the global dynamics of a SEIR model with information dependent vaccination. The basic reproduction number R0 is derived for the model, and it is shown that R0 gives the threshold dynamics in the sense that the disease-free equilibrium is globally asymptotically stable and the disease dies out if R0<1, while there exists at least one positive periodic solution and the disease is uniformly persistent when R0>1. Further, we give the approximation formula of R0. This answers the concerns presented in [B. Buonomo, A. d'Onofrio, D. Lacitignola, Modeling of pseudo-rational exemption to vaccination for SEIR diseases, J. Math. Anal. Appl. 404 (2013) 385-398]. Copyright © 2014 John Wiley & Sons, Ltd.

Zhao F.,Xidian University
Engineering Analysis with Boundary Elements | Year: 2013

A meshless Galerkin Pareto-optimal method is proposed for topology optimization of continuum structures in this paper. The compactly supported radial basis function (CSRBF) is used to create shape functions. The shape function is constructed by meshfree approximations based on a set of unstructured field nodes. Considering the Pareto-optimality theory, the initial single objective topology optimization problem is transformed into multi-objective problem. The optimum solution is traced via the Pareto-optimal frontier in a computationally effective manner. The optimal problem does not need to be solved directly. Finally, several examples are used to prove the validity and effectiveness of the proposed approach. © 2013 Elsevier Ltd. All rights reserved.

Zhang S.,Xidian University
Chemometrics and Intelligent Laboratory Systems | Year: 2015

Determination of protein structural class using a fast and suitable computational method has become a hot issue in protein science. Prediction of protein structural class for low-similarity sequences remains a challenge problem. In this study, a 111-dimensional feature vector is constructed to predict protein structural classes. Among the 111 features, 100 features based on pseudo-position specific scoring matrix (PsePSSM) are selected to reflect the evolutionary information and the sequence-order information, and the other 11 rational features based on predicted protein secondary structure sequences (PSSS) are designed in the previous works. To evaluate the performance of the proposed method (named by PSSS-PsePSSM), jackknife cross-validation tests are performed on three widely used benchmark datasets: 1189, 25PDB and 640. Our method achieves competitive performance on prediction accuracies, especially for the overall prediction accuracies for datasets 1189, 25PDB and 640, which reach 86.6%, 89.5% and 81.0%, respectively. The PSSS-PsePSSM algorithm also outperforms other existing methods, indicating that our proposed method is a cost-effective computational tool for protein structural class prediction. © 2015 Elsevier B.V.

Zhang H.-B.,Xidian University
International Journal of Control and Automation | Year: 2016

In this paper, a computational model for hybrid systems is defined. Based on this model, a partial order relation of hybrid systems is given and a lattice of hybrid systems is formalized. Armed with these notations, synthesis of hybrid systems is discussed. The synthesis can be seen as the operation of solving the least upper bound of members of the lattice. An example is given to illustrate the approach. © 2016 SERSC.

Qin P.-Y.,CSIRO | Jay Guo Y.,CSIRO | Ding C.,CSIRO | Ding C.,Xidian University
IEEE Transactions on Antennas and Propagation | Year: 2013

A new microstrip dual-band polarization reconfigurable antenna is presented for wireless local area network (WLAN) systems operating at 2.4 and 5.8 GHz. The antenna consists of a square microstrip patch that is aperture coupled to a microstrip line located along the diagonal line of the patch. The dual-band operation is realized by employing the TM10 and TM30 modes of the patch antenna. Four shorting posts are inserted into the patch to adjust the frequency ratio of the two modes. The center of each edge of the patch is connected to ground via a PIN diode for polarization switching. By switching between the different states of PIN diodes, the proposed antenna can radiate either horizontal, vertical, or 45° linear polarization in the two frequency bands. Measured results on reflection coefficients and radiation patterns agree well with numerical simulations. © 1963-2012 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.

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.

Wu S.-L.,Xidian University
Nonlinear Analysis: Real World Applications | Year: 2012

This paper is concerned with entire solutions of a bistable reactiondiffusion system modeling manenvironmentman epidemics, i.e., solutions defined for all times t ∈ R and for all points x ∈ R. It is known that the system has an increasing traveling wave solution with nonzero wave speed under some reasonable conditions. Using the comparison argument and sub-super-solution method, we construct some new entire solutions for the system which behave like two increasing traveling wave solutions propagating from both sides of the x-axis and annihilating at a finite time. © 2011 Elsevier Ltd. All rights reserved. © 2012 Elsevier Ltd. All rights reserved.

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.

Zhang L.,Hong Kong Polytechnic University | Yang M.,Hong Kong Polytechnic University | Feng X.,Xidian University
Proceedings of the IEEE International Conference on Computer Vision | Year: 2011

As a recently proposed technique, sparse representation based classification (SRC) has been widely used for face recognition (FR). SRC first codes a testing sample as a sparse linear combination of all the training samples, and then classifies the testing sample by evaluating which class leads to the minimum representation error. While the importance of sparsity is much emphasized in SRC and many related works, the use of collaborative representation (CR) in SRC is ignored by most literature. However, is it really the l 1-norm sparsity that improves the FR accuracy? This paper devotes to analyze the working mechanism of SRC, and indicates that it is the CR but not the l 1-norm sparsity that makes SRC powerful for face classification. Consequently, we propose a very simple yet much more efficient face classification scheme, namely CR based classification with regularized least square (CRC-RLS). The extensive experiments clearly show that CRC-RLS has very competitive classification results, while it has significantly less complexity than SRC. © 2011 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.

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.

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.

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.

Bai Z.,Xidian University
Mathematical Biosciences | Year: 2015

In this paper, we consider a delayed SEIRS model with pulse vaccination and varying total population size. The basic reproduction number R0 is derived, and it is shown that the disease-free periodic solution is globally attractive if R0 < 1, while the disease is uniformly persistent when R0 > 1. Our results really improve the results by Gao et al. (2007) [8], where they left the open problem of finding a sharp threshold which determines the eradication and uniform persistence. Numerical simulations are conducted to illustrate the analytical results and explore the influences of pulse vaccination and time delay on the spread of the disease. To the best of our knowledge, it is the first work to have the sharp threshold dynamics for impulsive epidemic models with the delay in the infected compartments. © 2015 Elsevier Inc.

Shi B.-Q.,Xidian University | Shi B.-Q.,Xian Jiaotong University | Liang J.,Xian 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.

Feng B.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

We develop a K-SVD algorithm based radar HRRP target recognition method, which can adaptively select the sparse decomposition coefficient based on test noise environment. Experimental results on measured data show our method obtains a better performance than PCA based method. © 2011 IEEE.

Qin P.-Y.,CSIRO | Guo Y.J.,CSIRO | Ding C.,CSIRO | Ding C.,Xidian University
IEEE Transactions on Antennas and Propagation | Year: 2013

A high gain beam switching pattern reconfigurable quasi-Yagi dipole antenna is presented for wireless local area network (WLAN) systems at 5.2 GHz. The antenna consists of a microstrip-to-coplanar stripline (CPS) balun, the length of which can be controlled by using PIN diodes. The change of the length of the balun allows the currents on the two arms of the dipole to have different phase differences, thereby making the antenna operate at three states with the E-plane maximum beam direction towards 20°, -20°, and 0°, respectively. In order to validate the design method, a prototype of the proposed antenna with a practical biasing network was fabricated and measured. Measured results on the reflection coefficients, radiation patterns, and realized gains for three operating states are provided, which agree well with the numerical simulations. © 1963-2012 IEEE.

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.

Li Q.,Xian Jiaotong University | Sun L.,Xian 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.

Cui Z.-W.,Xidian University
Guangzi Xuebao/Acta Photonica Sinica | Year: 2015

The scattering of an arbitrarily incident Bessel beam by complex particles with inclusions was investigated by utilizing the method of moments and its fast algorithm based on surface integral equations. The mathematical description of the electromagnetic field components of the arbitrarily incident Bessel beams were derived by using the vector expressions of zero-order Bessel beam in combination with rotation Euler angles. Based on equivalence principle, the surface integral equations were established, which could solve the scattering problems involving complex particles with inclusions of arbitrary shape and structure. The scattering of an arbitrarily incident Bessel beam by several selected particles with inclusions was simulated. The numerical results indicate that the Differential Scattering Cross Section (DSCS) for a Bessel beam is smaller than that for a plane wave and increases with the decreasing of the half-cone angle. Moreover, the position offset of the beam center decreases the DSCS, and the DSCS will be quite sensitive to the incident angles. The obtained results are expected to provide useful help for techniques of laser detection on particle, diagnosis, and manipulation. ©, 2015, Chinese Optical Society. All right reserved.

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.

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 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.

Sun B.,Xidian University | Ma W.,Tongji University
Information Sciences | Year: 2015

Multi-attribute group decision-making (MAGDM) has evoked increasing attention in recent years. Meanwhile, many valuable approaches have been developed to solve various MAGDM problems. In this paper, we consider a MAGDM problem in the presence of multi-attribute and multi-decision decision making with preference, namely the MA&MD decision problem. It involves the assignment of objects (actions), evaluated based on a set of conditional attributes, to pre-defined and preference-ordered multi-decision making. The actions are described by a finite set of conditional attributes and decision attributes. Both types of attribute take the values from their domain with preference order. In order to construct a comprehensive preference evaluation model that could be used to support the optimal choice task, we define two dominance relations, one on the condition attribute set and the other on the decision attribute set. We then present the lower and upper approximations of a preference relation defined by the decision attribute set based on a multi- decision preference dominance relation. Meanwhile, we propose an approach to decision making based on the rough set model established in this paper. The approach to decision making is derived from the lower approximation of decision classes with a preference dominance relation. The idea and decision rule are applied to solving a multi-agent conflict analysis decision problem. This method addresses limitations of the Pawlak conflict analysis model and thus improves on that model. Furthermore, to give practical significance to this management decision making approach, we present two extended models of the multi-decision preference dominance-based rough set as well as the corresponding decision making method. Moreover, we compare the proposed approach to previous studies of dominance-based rough set approaches to multiple attribute (criteria) decision making. The main contribution of this paper is twofold. One is to establish a generalization of the classical dominance-based rough set approach, i.e., the model of multi-decision preference dominance-based rough set. Another is to present a new approach to deal with the multi-agent conflict analysis decision making problem based on the proposed multi-decision rough set approach. © 2015 Elsevier Inc. All rights reserved.

Wang H.,Dalian Ocean University | Wang H.,Xidian University
IEEE Transactions on Services Computing | Year: 2013

Recently, cloud computing rapidly expands as an alternative to conventional computing due to it can provide a flexible, dynamic and resilient infrastructure for both academic and business environments. In public cloud environment, the client moves its data to public cloud server (PCS) and cannot control its remote data. Thus, information security is an important problem in public cloud storage, such as data confidentiality, integrity, and availability. In some cases, the client has no ability to check its remote data possession, such as the client is in prison because of committing crime, on the ocean-going vessel, in the battlefield because of the war, and so on. It has to delegate the remote data possession checking task to some proxy. In this paper, we study proxy provable data possession (PPDP). In public clouds, PPDP is a matter of crucial importance when the client cannot perform the remote data possession checking. We study the PPDP system model, the security model, and the design method. Based on the bilinear pairing technique, we design an efficient PPDP protocol. Through security analysis and performance analysis, our protocol is provable secure and efficient. © 2008-2012 IEEE.

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.

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.

Yu J.-X.,Xidian University
Jiaotong Yunshu Xitong Gongcheng Yu Xinxi/Journal of Transportation Systems Engineering and Information Technology | Year: 2015

This paper calculates the Theil coefficient and Gini coefficient of the highway development and economic development, studies the spatial difference and correlation of highway and economic development. The calculations are that: The spatial difference of highway traffic infrastructural construction is significant. The difference of the spatial and temporal variation of highway construction has a tendency to increase in the long run. And the difference mostly comes from the regional differences of four economic regions;The difference of the spatial and temporal variation of economic development is little than the one's of highway. The difference main comes from the difference between four economic regions, and the influence degree is up to 70%. There are significant correlation between the difference of spatial and temporal variation of highway and the ones of economic development. Copyright © 2015 by Science Press.

Liu H.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

Radar automatic target recognition (RATR) is an important function for modern radar. Target high resolution range profile (HRRP) contains target structure signatures, such as target size, scatterer distribution, etc., thereby radar HRRP target recognition has received intensive attention from the RATR community. Statistical modeling of target HRRPs is the key stage for HRRP statistical recognition, which including model selection and parameter estimation. In this paper, we introduce the recent progress in HRRP based RATR, including the statistical modelling algorithms of HRRP data, robust recognition algorithms for low signal noise ratio(SNR) case, and some results based on the measured data. © 2011 IEEE.

Yan J.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

An improved Track-Before-Detect Algorithm based on Particle Smoothing (PS-TBD) is proposed, with the consideration of the computation resources. Simulation results show that the proposed algorithm can improve effectively the target state estimation precision within a short time. © 2011 IEEE.

Min B.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

Because of the long integration time of geosynchronous earth orbit synthetic aperture radar (GEO SAR), the imaging model and algorithm of low earth orbit (LEO) SAR are not suitable for GEO SAR. Thus, this paper establishes the echo model of the GEO SAR by using the high order range model based on the characters of the GEO SAR movements. Then, the two-dimensional (2-D) spectrum is derived by the method of series reversion (MSR), based on which a new imaging algorithm used for GEO SAR is presented. Finally, simulation results of point targets prove the accuracy and validity of the proposed algorithm. © 2011 IEEE.

Zhao X.,Xidian University
International Journal of Network Security | Year: 2012

Traitor tracing is needed because some users in broadcast encryption system may give out their decryption keys to construct pirate decoders. Recently, Liu and Yuan de-scribed a trace and revoke systems with short cipher-texts. In this paper, we show that their scheme can-not achieve traitor tracing, since any receiver can decide whether the given ciphertext is well-formed or not so as to decide whether the system is now in normal broadcast-ing mode or in traitor tracing mode. Thus, any user can construct decoders that will decrypt well-formed cipher-texts (ciphertexts for normal broadcasting) and refuse the badly-formed ciphertexts (ciphertexts for traitor tracing), so that traitors cannot be identi-ed. In such case, inno-cent users will be framed. We provide an amendment to their scheme and render it useful in traitor tracing against both perfect and imperfect decoders.

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.

Yang C.,Xidian University
2013 IEEE/CIC International Conference on Communications in China, ICCC 2013 | Year: 2013

Both fairness and efficiency are natural performance metrics of radio resource management (RRM) in wireless communication systems. However, taking both of them into account simultaneously in one formulated RRM model is non-trivial, because promoting the one typically involves compromising on the other one. In this paper, both symmetric and asymmetric cooperative game-theoretical rate control games are formulated in one unified preference function design. Closed-form of optimal rates are derived for two-player game to achieve optimal tradeoffs between Nash fairness and Nash axiomatic efficiency. We illustrate and provide the analyzed results of both symmetric and asymmetric rate control schemes. Finally, we conclude that the optimal setting of bargaining powers can help to improve both fairness and efficiency of the rate control. © 2013 IEEE.

Su Y.,Xidian University
International Journal of Systems Science | Year: 2015

A simple nonlinear observer is proposed for a class of uncertain nonlinear multiple-input-multiple-output mechanical systems whose dynamics are first-order differentiable. The proposed observer is constructed without any detailed model knowledge of the system and the observer gains are easily chosen. Another interesting features of the proposed observer include that it is more immune to noise and is high robust against parameters variations, and thus it is readily implemented. Lyapunov's direct method is employed to prove global asymptotic convergent observation. Extensive simulations are presented to illustrate the effectiveness and improved performance of the proposed observer. © 2014 Taylor & Francis.

Wang L.,Xidian University | Guan B.-R.,Hangzhou Dianzi University
Progress in Electromagnetics Research Letters | Year: 2011

A novel and compact dual-mode defected ground structure (DGS) resonator is presented. Distinct characteristics of the proposed resonator are investigated. Using this type of resonator, a bandpass filter with the center frequency of 2.38 GHz and the fractional bandwidth of 6.7% is simulated and fabricated. The results show that this filter not only has an inherent transmission zero near the passband, but also has a very wide upper stopband with rejection better than 20 dB up to about 12 GHz.

Yang Q.,Xidian University
Applied Optics | Year: 2016

This paper presents a compact high-resolution Littrow conical diffraction spectrometer (LCDS) that includes an echelle grating for horizontally dispersing the incident light beam into several high diffraction orders, a prism for vertically separating the overlapping diffraction orders, and a shared focusing lens used for both the incident and dispersed beams. The unique design of the optics enables the LCDS to give high dispersion on the detector without requiring a large field of view and, therefore, to achieve the benefits of high spectral resolution and compactness. The use of the Littrow conical diffraction coupled with the shared focusing lens makes the LCDS more compact. The formulas of the footprint of the dispersed spectra are derived, and the numerical simulation is given. The design calculations for application of the LCDS to an optical coherence tomography system are illustrated by an example. © 2016 Optical Society of America.

Wang C.,Xian 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.

Shi Y.,Xidian University | Chan C.H.,City University of Hong Kong
Journal of the Optical Society of America A: Optics and Image Science, and Vision | Year: 2010

In this paper, we present the multilevel Green's function interpolation method (MLGFIM) for analyses of three-dimensional doubly periodic structures consisting of dielectric media and conducting objects. The volume integral equation (VIE) and surface integral equation (SIE) are adopted, respectively, for the inhomogeneous dielectric and conducting objects in a unit cell. Conformal basis functions defined on curvilinear hexahedron and quadrilateral elements are used to solve the volume/surface integral equation (VSIE). Periodic boundary conditions are introduced at the boundaries of the unit cell. Computation of the space-domain Green's function is accelerated by means of Ewald's transformation. A periodic octary-cube-tree scheme is developed to allow adaptation of the MLGFIM for analyses of doubly periodic structures. The proposed algorithm is first validated by comparison with published data in the open literature. More complex periodic structures, such as dielectric coated conducting shells, folded dielectric structures, photonic bandgap structures, and split ring resonators (SRRs), are then simulated to illustrate that the MLGFIM has a computational complexity of ON when applied to periodic structures. © 2010 Optical Society of America.

Zhang X.,Xianyang Normal University | Feng X.,Xidian University
Multimedia Tools and Applications | Year: 2015

This paper presents a new image denoising algorithm. Our method is inspired by locally adaptive window-based denoising using maximum likelihood (LAWML). In the research, we find, as with wavelet coefficients, the gradient image coefficients can also be modeled as zero-mean Gaussian random variables with high local correlation. So, we implement the local adaptive Wiener filter in the gradient domain. But unlike LAWML, the layered denoising is adopted in our method. At the same time, the relation between wavelet-based and diffusion-based denoising method is disclosed further. The tests demonstrate the proposed method gets the desired results both subjectively and objectively compared to the related gradient domain algorithms and wavelet-based image denoising methods. At the same time, the tests also show the proposed method outperforms some other diffusion filters and waveletbased methods and Non-Local means (NL-means) filter in most cases. © Springer Science+Business Media New York 2014.

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.

The fractional Fourier transform (FRFT) plays an important role in many fields of optics and signal processing. Many results in Fourier analysis have been extended to the FRFT, including the convolution and correlation theorems. However, the convolution and correlation theorems don't have the elegance and simplicity comparable to that of the Fourier transform (FT). In this paper, we will propose a new convolution as well as correlation structure for FRFT which have similar time domain to frequency domain mapping results as the classical FT. First, we introduce a new convolution structure for the FRFT, which is expressed by a one dimensional integral and easy to implement in filter design. The conventional convolution theorem in FT domain is shown to be special cases of our achieved results. Then, we derive a convolution theorem for discrete time signal in discrete time FRFT (DTFRFT) domain. Last, based on the new convolution structure, we present a new kind of correlation operation for the FRFT that also generalizes very nicely the classical result for FT. © 2016 Elsevier GmbH. All rights reserved.

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.

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.

Huang J.,Hunan University of Science and Technology | Zhang J.,Xidian University
International Journal of Digital Content Technology and its Applications | Year: 2010

In practical applications, Wireless Sensor Networks generate massive data streams with the dual attributes in geography and optimization domain. Energy source of sensor nodes in WSN is usually limited; Data streams transmission is known to be the largest consumer of energy in WSN. Therefore, reduce the total data transmission and maximizing energy efficiency is the major challenge in WSN. In addition, sensor data points usually have attributes in the optimization and the geography domain. In most existing clustering algorithms, the similarity measurement mainly takes the non-geometric attributes into consideration. However, in many real applications, the geometric attributes are what users are concerned about. Motivated by the above, this paper presents an efficient Distributed Dual Cluster Algorithm Based on Grid (DDCG) for sensor streams to minimize sensor nodes energy consumption and clustering results in which a cluster has not only high proximity in geometrical domain, but also high similarity in optimization domain. To solve the dual attributes problem, the proposed DCG algorithm combines the information in both geographic and non-geographic attributes by constructing a super-rectangular grid cell and merging the grid cells into connected region (cluster). To minimize sensor nodes energy consumption, DCCG algorithm consists of two levels of clustering: local clustering and global clustering. First, clustering is conducted at group heads with a local clustering algorithm DCG, and the features of local clusters are extracted. Second, local features are sent to sink where global clustering is obtained based on those features. Experiments on Synthetic datasets show that the algorithm DDCG has higher efficiency, lower energy consumption.

Qiao S.,Xidian University
Discrete Optimization | Year: 2010

Let G be a simple graph with the vertex set V(G) and α be a real number with α≠0. The zeroth-order general Randi index of G is defined as Rα0(G)=∑v∈V(G)dα(v), where d(v) denotes the degree of the vertex v in G. A graph G is called a quasi-tree graph, if there exists a vertex u∈V(G) such that G[V(G)\u] is a tree. In this paper, we characterize the extremal quasi-tree graphs containing cycles with the minimum and maximum values of the zeroth-order general Randi index for α in different intervals. © 2010 Elsevier B.V.

Chen W.,Xidian University | Zhang Z.,Qufu Normal University
Fuzzy Sets and Systems | Year: 2010

This paper addresses the problem of globally stable adaptive backstepping output-feedback tracking control for a class of nonlinear systems with unknown high-frequency gain sign. The fuzzy systems are used as feedforward compensators to model some system functions depending on the reference signal. Thus, the global stability of closed-loop system can be guaranteed under the assumption that the unknown system functions are bounded by partly known nonlinear functions. The other advantage of the proposed control scheme is that the designer can determine the approximation domain a priori via the bound of the reference signal, which is very important for the choice of the centers and widths of membership functions. Moreover, the Nussbaum-type function is employed to deal with the unknown high-frequency gain sign. Two simulation examples are provided to illustrate the feasibility of control scheme presented in this paper. © 2009 Elsevier B.V. All rights reserved.

Qu X.,Xidian University
International journal of nanomedicine | Year: 2012

Due to the efficient bioconjugation and highly photothermal effect, gold nanoparticles can stain receptor-overexpressing cancer cells through specific targeting of ligands to receptors, strongly absorb specific light and efficiently convert it into heat based on the property of surface plasmon resonance, and then induce the localized protein denaturation and cell death. Two gold nanoparticle-antibody conjugates, gold-BerH2 antibody (anti-CD30 receptor) and gold-ACT1 antibody (anti-CD25-receptor), were synthesized. Gold-BerH2 conjugates can specifically bind to the surface of L-428 Hodgkin's cells, and gold-ACT1 conjugates were used for the control. The gold nanoparticle-induced L-428 cell-killing experiments were implemented with different experimental parameters. At a relatively low concentration of gold and short incubation time, the influence of cytotoxicity of gold on cell viability can be overlooked. Under laser irradiation at suitable power, the high killing efficiency of gold-targeted L-428 cells was achieved, but little damage was done to nontargeted cancer cells. Gold nanoparticle-mediated photothermal therapy provides a relatively safe therapeutic technique for cancer treatment.

Liu Y.,Xidian University | Shang F.,Duke University
IEEE Signal Processing Letters | Year: 2013

Most recent low-rank tensor completion algorithms are based on tensor nuclear norm minimization problems. The convex relaxation problem of tensor $n$-rank minimization has to be solved iteratively and involves multiple singular value decompositions (SVDs) at each iteration, and thus such algorithms suffer from high computation cost. In this letter, we propose an efficient low-rank tensor completion approach. First, we introduce a matrix factorization idea into the tensor nuclear norm model, and then can achieve a much smaller scale matrix nuclear norm minimization problem. Moreover, we develop an efficient iterative scheme for solving the proposed model with orthogonality constraint. Our extensive evaluation results validate both the effectiveness and efficiency of the proposed approach. © 1994-2012 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.

Tian H.,Northwestern Polytechnical University | Fan H.,Northwestern Polytechnical University | Guo H.,Xidian University | Song N.,Northwestern Polytechnical University
Sensors and Actuators, B: Chemical | Year: 2014

A hybrid nanostructure of carbon with ZnO nanoparticles (NPs) was synthesized by grafting glucose on the surface of the ZnO NPs as the precursor and heating at 180 C for 30 min, which morphological feature was characterized as nanoparticles with an average diameter of 20-25 nm. Transmission electron microscopy (TEM) images revealed that the ZnO/C nanostructures preserved good dispersity and uniformity. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), N2 adsorption and gas-sensing measurements were performed to study the structure and the gas-sensing properties of the ZnO/C nanostructures. The gas-sensing properties demonstrated that the sensors based on the ZnO/C nanostructures exhibited a much higher gas response to acetone and ethanol vapor than the sensors based on the pure ZnO nanoparticles and the mechanism was also discussed. © 2014 Elsevier B.V.

Yang L.,Xidian University
Procedia Engineering | Year: 2011

Ensemble learning is a learning method where a collection of a finite number of classifiers is trained for the same classification task and thus it can gain better performance at the cost of computation. Previous research has proved that it may be better to ensemble many instead of all of classifiers at hand. Thus classifiers selection became a crucial problem for ensemble learning. To select the best classifier set from a pool of classifiers, the classifier diversity is the most important property to be considered. In this paper, a kind of selection method based on accuracy and diversity is proposed in order to achieve better classification performance. Classifiers correlation in our method is calculated using Q statistics diversity measures based on correlation between errors. Experiments were carried out on five data sets from UCI Machine Learning Repository. Twenty classifiers and six combination rules were included in our experiments. The experimental results are encouraging and validate the effectiveness of the proposed classifiers selection method. © 2011 Published by Elsevier Ltd.

Lu D.,Xidian University | Wu R.,Civil Aviation University of China
International Journal of Digital Content Technology and its Applications | Year: 2011

In this paper, a two stage GPS anti-jamming processor based on subspace and self-coherent property of the C/A code is proposed. Firstly, the array received signals are projected onto the interference orthogonal subspace to suppress interferences. Then direction of arrival (DOA) of GPS signal is obtained by self-coherent MUSIC and the free interference signals are synthesized by self-coherent estimated DOA. The new anti-jamming method could play the respective advantages of each stage. Simulation experiment results show the effectiveness of the new algorithm.

Bai Z.,Xidian University
Mathematical Biosciences and Engineering | Year: 2015

Threshold dynamics of epidemic models in periodic environments attract more attention. But there are few papers which are concerned with the case where the infected compartments satisfy a delay differential equation. For this reason, we investigate the dynamical behavior of a periodic SIR model with delay in an infected compartment. We first introduce the basic reproduction number R0 for the model, and then show that it can act as a threshold parameter that determines the uniform persistence or extinction of the disease. Numerical simulations are performed to confirm the analytical results and illustrate the dependence of R0 on the seasonality and the latent period.

Wen Y.,Columbia University | Lu Y.,East China Normal University | Yan J.,Shanghai JiaoTong University | Zhou Z.,Columbia University | And 2 more authors.
IEEE Transactions on Intelligent Transportation Systems | Year: 2011

An algorithm for license plate recognition (LPR) applied to the intelligent transportation system is proposed on the basis of a novel shadow removal technique and character recognition algorithms. This paper has two major contributions. One contribution is a new binary method, i.e., the shadow removal method, which is based on the improved Bernsen algorithm combined with the Gaussian filter. Our second contribution is a character recognition algorithm known as support vector machine (SVM) integration. In SVM integration, character features are extracted from the elastic mesh, and the entire address character string is taken as the object of study, as opposed to a single character. This paper also presents improved techniques for image tilt correction and image gray enhancement. Our algorithm is robust to the variance of illumination, view angle, position, size, and color of the license plates when working in a complex environment. The algorithm was tested with 9026 images, such as natural-scene vehicle images using different backgrounds and ambient illumination particularly for low-resolution images. The license plates were properly located and segmented as 97.16% and 98.34%, respectively. The optical character recognition system is the SVM integration with different character features, whose performance for numerals, Kana, and address recognition reached 99.5%, 98.6%, and 97.8%, respectively. Combining the preceding tests, the overall performance of success for the license plate achieves 93.54% when the system is used for LPR in various complex conditions. © 2006 IEEE.

Zheng J.,Xidian University
IEEE Wireless Communications Letters | Year: 2015

In the literature, the pre-coding aided spatial modulation (PSM) is designed only for the symmetric and the underdetermined multiple-input multiple-output (MIMO) systems. In this letter, we study the PSM in the over-determined MIMO system where the receive antenna subset (RAS) selection is considered. The optimal selection criterion is first given, and a fast greedy incremental algorithm is then proposed. The proposed algorithm constructs the RAS by adding antennas one by one, where the low-complexity recursive computation of the matrix inverse can be further employed. Simulation results show that the proposed fast algorithm can achieve most of the antenna selection gain with very low complexity. © 2012 IEEE.

Wang Y.,Xidian University
International Journal of Pattern Recognition and Artificial Intelligence | Year: 2010

In this paper, we propose a uniform enhancement approach called smoothing function method, which can cooperate any optimization algorithm and improve its performance. The method has two phases. In the first phase, a smoothing function is constructed by using a properly truncated Fourier series. It can preserve the overall shape of the original objective function but eliminate many of its local optimal points, thus it can well approach the objective function. Then, the optimal solution of the smoothing function is searched by an optimization algorithm (e.g. traditional algorithm or evolutionary algorithm) so that the search becomes much easier. In the second phase, we switch to optimize the original function for some iterations by using the best solution(s) obtained in phase 1 as an initial point (population). Thereafter, the smoothing function is updated in order to approximate the original function more accurately. These two phases are repeated until the best solutions obtained in several successively second phases cannot be improved obviously. In this manner, any optimization algorithm will become much easier in searching optimal solution. Finally, we use the proposed approach to enhance two typical optimization algorithms: Powell direct algorithm and a simple genetic algorithm. The simulation results on ten challenging benchmarks indicate the proposed approach can effectively improve the performance of these two algorithms. © 2010 World Scientific Publishing Company.

Chen H.,Xidian University
Advance Journal of Food Science and Technology | Year: 2015

Badminton is a sports item, its competitive feature is quite strong, therefore, the timely recovery of fatigue for badminton players is very important, which is related to the improvement of athlete's ability. This study is based on the interpretation of motion fatigue, taking it as the breakthrough point, by means of analyzing the parts that caused the fatigue, combined with the characteristics of badminton, it discusses the recovery method of nutrition supplement for badminton athletes. © Maxwell Scientific Organization, 2015.

Zhang S.,Xidian University
Microwave and Optical Technology Letters | Year: 2016

This paper proposes a novel dual-band in-phase reflection characteristic high impedance surface (HIS) by using two-layer edge located vias and interdigital structures (TELI-HIS). It has simple structure and compact size, and is easy for dual-frequency tuning. Parametric study and working mechanism of it are presented. Through the destructive interference between the reflected wave produced by the HIS and the metal part of antennas, the TELI-HIS is employed to reduce the in-band RCS of dual-band microstrip patch antenna array. Compared with the traditional RCS reduction technique, the proposed method can reduce the antenna in-band RCS without radiation performance degradation. Simulation and measurement show that the RCS in both operating bands are reduced by 11.5 dBsm at least, and the maximum gain and the return loss are coincident to the original antenna array. © 2016 Wiley Periodicals, Inc.

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.

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.

Fan K.-Q.,Xidian University | Fan K.-Q.,Kansas State University | Zhang P.-F.,Kansas State University | Pei Z.J.,Kansas State University
Renewable Energy | Year: 2013

Feedstock supply is one of the key obstacles for cost-effective production of cellulosic biofuels. This paper proposes an assessment model to study the feedstock costs, energy consumption, and CO 2 emissions associated with collecting and transporting cellulosic biomass from farm to storage sites. To illustrate the utility of the proposed model, four logistics options for collecting and transporting corn stover are studied: (A) round bales via tractor, (B) rectangular bales via tractor, (C) round bales via tractor (on-farm) and truck (road), and (D) rectangular bales via tractor and truck. Results show that option A is the lowest-cost option when storage capacity is less than 110,000 ton. For larger storage capacity, option D is more cost-effective. In terms of energy consumption and CO 2 emissions, option A consumes the least energy and generates the least CO 2 emissions when storage capacity is less than 45,000 ton. For larger storage capacity, option D performs better. © 2012 Elsevier Ltd.

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.

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.

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.

Li L.,Xian Institute of Post and Telecommunications | Zhang J.,Xian Institute of Post and Telecommunications | Zhang J.,Xidian University
Knowledge-Based Systems | Year: 2010

Attribute reduction in fuzzy concept lattices based on the kind of transitive regular implication operator (T implication in short) is introduced and investigated. We first propose a kind of fuzzy concept lattices by using T implication in a fuzzy formal context at a level δ∈I T⊆[0,1] with respect to T implication. Then we introduce the notion of δ-reducts in a fuzzy formal context and give some equivalent characterizations of δ-consistent sets to determine δ-reducts. Based on δ-reducts, we divide attributes into three types (at a level δ) and establish some characterization theorems to determine the type of an attribute. © 2010 Elsevier B.V. All rights reserved.

Kong Y.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

To deal with the beam tracking issue in phased array when interferences are removed by adaptive beamforming, a new generalized sidelobe canceller(GSC) that can realize beam tracking is proposed in this paper. First of all, with the estimated angles and the current training samples, it constructs a new reduced-dimension blocking matrix with the number of interferences as the number of columns, which is realized through linear combinations of column vectors in the array covariance matrix, without eigen-decomposition. Then the reduced-dimension blocking matrix is worked on both sum and difference beams, estimating adaptive sum and difference weights and realizing the anti-jamming exporting. Finally, it realizes beam tracking through the monopulse technology. This reduced-dimension generalized sidelobe canceller (GSC) can suppress interferences effectively when tracking the target, with the advantages of simple structure, less computation and little distortion of monopulse ratio curve. The processing results of simulation and measured data show the effectiveness and advantages of this reduced-dimension generalized sidelobe canceller (GSC). © 2011 IEEE.

Zhang D.T.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

The fractal dimension of sea clutter is estimated and its multifractal features are analyzed in this paper. A new method based on the difference between multifractal spectra of sea clutter and target plus sea clutter is proposed to detect targets in sea clutter. The verification of real sea clutter shows that this method is useful and has low computation burden. So it provides a new idea and an effective method to detect low observable targets in sea clutter. © 2011 IEEE.

Shi P.,Xidian University
Mechanics Based Design of Structures and Machines | Year: 2016

A hollow functionally graded composite cylinder under static torsion, which consists of an inner and outer elastic circular tube with a cylindrical interface crack, is studied in this work. By utilizing Fourier integral transform method, the mixed boundary value problem is reduced to a Cauchy singular integral equation, from which the numerical results of the stress intensity factor are obtained by the Lobatto–Chebyshev quadrature technique. Numerical results demonstrate the coupled effects of geometrical, physical, and functionally graded parameters on the interfacial fracture behavior. 2016 Copyright © Taylor & Francis Group, LLC

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.

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.

Shen C.,Beijing Jiaotong University | Shen C.,Xidian University | Li W.-C.,National Tsing Hua University | Chang T.-H.,National Taiwan University of Science and Technology
IEEE Transactions on Signal Processing | Year: 2014

This paper considers the transmitter design for wireless information and energy transfer (WIET) in a multiple-input single-output (MISO) interference channel (IFC). The design problem is to maximize the system throughput subject to individual energy harvesting constraints and power constraints. It is observed that the ideal scheme, where the receivers simultaneously perform information detection (ID) and energy harvesting (EH) from the received signal, may not always achieve the best tradeoff between information transfer and energy harvesting, but simple practical schemes based on time splitting may perform better. We therefore propose two practical time splitting schemes, namely the time-division mode switching (TDMS) and time-division multiple access (TDMA), in addition to the existing power splitting (PS) scheme. In the two-user scenario, we show that beamforming is optimal to all the schemes. Moreover, the design problems associated with the TDMS and TDMA schemes admit semi-analytical solutions. In the general K -user scenario, a successive convex approximation method is proposed to handle the WIET problems associated with the ideal scheme, the PS scheme and the TDMA scheme, which are known NP-hard in general. Simulation results show that none of the schemes under consideration can always dominate another in terms of the sum rate performance. Specifically, it is observed that stronger cross-link channel power improves the achievable sum rate of time splitting schemes but degrades the sum rate performance of the ideal scheme and PS scheme. As a result, time splitting schemes can outperform the ideal scheme and the PS scheme in interference dominated scenarios. © 1991-2012 IEEE.

Zhao F.,Xidian University
Finite Elements in Analysis and Design | Year: 2014

A nodal variable ESO (BESO) method is proposed for topology optimization of continuum structures in this paper. The initial discrete-valued topology optimization problem is established as an optimization problem based on continuous design variables by employing a material density field into the design domain. The density field, with the Shepard family of interpolation, is mapped on the design space defined by a finite number of nodal density variables. The employed interpolation scheme has an explicit form and satisfies non-negative and range-restricted properties required by a physically significant density interpolation. It has the ability to deal with more complex spatial distribution of the material density within an individual element, as compared with the conventional elementwise design variable methods. Numerical examples demonstrate the validity and effectiveness of the improved method. © 2014 Elsevier B.V.

Zhang H.,Xidian University | Zhang H.,Xian University of Posts and Telecommunications | Fan J.-L.,Communication University of China
Guangzi Xuebao/Acta Photonica Sinica | Year: 2013

Arimoto entropy is a general form of entropy. Firstly, a representation error on the two-dimensional Arimoto entropy is pointed out, and a correct two-dimensional Arimoto entropy thresholding method is given; a two-dimensional Arimoto entropy linear-type thresholding method and its fast recursive formula are proposed; Arimoto entropy formula parameter selection and the segmentation performance assessment according to the ground truth images are discussed. A large number of segmentation experiment results show that the two-dimensional Arimoto entropy linear-type thresholding method has at least a similar effect with the two-dimensional Arimoto entropy & the two-dimensional Renyi entropy linear-type thresholding; in the cases of the more image edge and noise information, the two-dimensional Arimoto entropy linear-type method is better than the two-dimensional Arimoto entropy & the two-dimensional Renyi entropy linear-type method, is a effective thresholding method.

Guo J.,Xidian University | Li Z.,Martin Luther University of Halle Wittenberg
Asian Journal of Control | Year: 2010

To solve the problem of deadlock prevention for timed Petri nets, an effective deadlock prevention policy based on elementary siphons is proposed in this paper. Without enumerating reachable markings, deadlock prevention is achieved by adding monitors for elementary siphons, increasing control depth variables when necessary, and removing implicit, liveness-restricted and redundant control places. The final supervisor is live. First, a timed Petri net is stretched into a stretched Petri net (SPN). Unchanging the system performance, each transition in the SPN has a unit delay time. Then the siphon-control-based approach is applied. Monitors computed according to the marking constraints are added to the SPN model to ensure all strict minimal siphons in the net invariant-controlled. A liveness-enforcing supervisor with simple structure can be obtained by reverting the SPN into a TdPN. © 2010 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society.

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.

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.

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.

Yang F.,Xidian University | Wan S.,Northwestern Polytechnical University | Xie Q.,Huawei | Wu H.R.,RMIT University
IEEE Transactions on Circuits and Systems for Video Technology | Year: 2010

A no-reference (NR) quality measure for networked video is introduced using information extracted from the compressed bit stream without resorting to complete video decoding. This NR video quality assessment measure accounts for three key factors which affect the overall perceived picture quality of networked video, namely, picture distortion caused by quantization, quality degradation due to packet loss and error propagation, and temporal effects of the human visual system. First, the picture quality in the spatial domain is measured, for each frame, relative to quantization under an error-free transmission condition. Second, picture quality is evaluated with respect to packet loss and the subsequent error propagation. The video frame quality in the spatial domain is, therefore, jointly determined by coding distortion and packet loss. Third, a pooling scheme is devised as the last step of the proposed quality measure to capture the perceived quality degradation in the temporal domain. The results obtained by performance evaluations using MPEG-4 coded video streams have demonstrated the effectiveness of the proposed NR video quality metric. © 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.

Zhi X.-B.,Xidian University | Fan J.-L.,University of Posts and Telecommunications | Zhao F.,University of Posts and Telecommunications
Pattern Recognition | Year: 2013

Linear Discriminant Analysis (LDA) is a classical statistical approach for supervised feature extraction and dimensionality reduction, hard c-means (HCM) is a classical unsupervised learning algorithm for clustering. Based on the analysis of the relationship between LDA and HCM, Linear Discriminant Analysis-guided adaptive subspace hard c-means clustering algorithm (LDA-HCM) had been proposed. LDA-HCM combines LDA and HCM into a coherent framework and can adaptively reduce the dimension of data while performing data clustering simultaneously. Seeing that LDA-HCM is still a hard clustering algorithm, we consider the fuzzy extension version of LDA-HCM in this paper. To this end, firstly, we propose a new optimization criterion of Fuzzy Linear Discriminant Analysis (FLDA) by extending the value of membership function in classical LDA from binary 0 or 1 into closed interval [0, 1]. In the meantime, we present an efficient algorithm for the proposed FLDA. Secondly, we show the close relationship between FLDA and Maximum Entropy Fuzzy Clustering Algorithm (MEFCA): they both are maximizing fuzzy between-class scatter and minimizing within-class scatter simultaneously. Finally, based on the above analysis, combining FLDA and MEFCA into a joint framework, we propose fuzzy Linear Discriminant Analysis-guided maximum entropy fuzzy clustering algorithm (FLDA-MEFCA). LDA-MEFCA is a natural and effective fuzzy extension of LDA-HCM. Due to the introduction of soft decision strategy, FLDA-MEFCA can yield fuzzy partition of data set and is more flexible than LDA-HCM. We also give the convergence proof of FLDA-MEFCA. Extensive experiments on a collection of benchmark data sets are presented to show the effectiveness of the proposed algorithm. © 2012 Elsevier Ltd.

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.

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.

Sun W.,Xidian University
Optik | Year: 2013

Based on the physical model of atmospheric scattering and the optical reflectance imaging model, three major factors which affect the effect of fog removal are discussed in detail, dark channel phenomenon is explained via the optical model, and an approach for solving the parameter in the atmospheric scattering model is rigorously derived from a new perspective. Using gray-scale opening operation and fast joint bilateral filtering techniques, the proposed algorithm can effectively obtain the global atmospheric light and greatly improve the speed and accuracy of atmospheric scattering function solving. Finally, the scene albedo is recovered by inverting this model. Compared with existing algorithms, complexity of the proposed method is only a linear function of the number of input image pixels and this allows a very fast implementation. The simulation results show that the processing time of images with a resolution of 576*768 is only 1.7 s; Results on a variety of outdoor foggy images demonstrate that the proposed method achieves good restoration for contrast and color fidelity, resulting in a great improvement in image visibility. © 2013 Elsevier GmbH.

Gouesbet G.,INSA Rouen | Wang J.J.,INSA Rouen | Wang J.J.,Xidian University
Optics Communications | Year: 2012

The generalized Lorenz-Mie theories for a homogeneous sphere (interaction between an electromagnetic arbitrary shaped beam and a sphere defined by its diameter and its complex refractive index), and for other particles as well (such as cylindrical particles, with circular or elliptical cross-sections) have been developed by using the Bromwich method. Conversely, this method cannot be used for spheroidal particles. Whether it is possible or not to use the Bromwich method implies a certain number of consequences concerning (i) the definition of TM- and TE-waves, (ii) the definition of genuine beam shape coefficients to describe the beam, (iii) the possibility of developing a localized beam model to describe the illuminating beam. These three issues may be enlightened by referring to the properties of the Bromwich method. © 2012 Elsevier B.V. All rights reserved.

Xia Y.,Xidian University | Sun J.,CAS Beijing National Laboratory for Molecular | Liang D.,CAS Beijing National Laboratory for Molecular
Langmuir | Year: 2014

Biological membranes are heterogeneous systems. Their functions are closely related to the lipid lateral segregation in the presence of membrane proteins. In this work, we designed two peptides, amphiphilic cationic peptides K 3L8K3and nonamphiphilic peptides K 20, and studied their interactions with binary liposomes in different phases (Lα, Lβ′, and L α/Lβ′). As mimics of membrane proteins, both K3L8K3and K20can cause the liposomes to aggregate, fuse, or leak. These processes were closely related to the phases of liposomes. For the liposomes in Lαphase, heavy aggregation, fusion, and leakage were observed in the presence of either K 20or K3L8K3. For the liposomes in Lβ′ phase, neither K3L8K 3nor K20can induce fusion or leakage. For the liposomes in Lα/Lβ′ phase, K3L 8K3caused the liposomes to aggregate, fuse, and leak, while K20only led to aggregation. The kinetics of aggregation, fusion, and leakage in each phase were recorded, and they were related to the lipid demixing in the presence of the peptide. Our work not only gained insight into the effect of the lipid demixing on the interactions between peptide and membrane, but also helped in developing drug delivery vehicles with liposomes as the platform. © 2014 American Chemical Society.

Shi Y.,Xidian University | Chan C.H.,City University of Hong Kong
IEEE Transactions on Antennas and Propagation | Year: 2012

A parallelized multilevel Green's function interpolation method (MLGFIM) accelerated by fast Fourier transform (FFT) technique is proposed. The difficulties in applying various improved interpolation schemes to effectively reduce the number of interpolation points are overcome by using the FFT technique. In order to accelerate the convergence property of the iterative solution using the proposed algorithm, a recently proposed preconditioning scheme, i.e., multiplicative Calderon preconditioner is adopted to transform the first kind integral operator to the second kind, albeit an increase of computer memory storage requirement. An OpenMP parallel implementation of the MLGFIM-FFT algorithm on a share-memory computer system is developed to analyze various electrically large electromagnetic scattering problems including a NASA almond, a 20-wavelength cylinder capped with two half spheres, and a 37-wavelength cylinder array. Numerical results illustrate good computational performance of the proposed algorithm. © 1963-2012 IEEE.

Yang Y.,Xidian University
Sheng wu yi xue gong cheng xue za zhi = Journal of biomedical engineering = Shengwu yixue gongchengxue zazhi | Year: 2010

It is difficult to extract signals under Low Signal Noise Ratio in biomedical signal processing. The elimination of movement artifact is really a bottleneck. A new solution for the movement artifact in pulse signal is proposed in this paper. According to pulse signal features, the signal is decomposed by using wavelet transform firstly. Then empirical mode decomposition (EMD) is applied to the wavelet coefficients in frequency band of useful signals, thus the signal and movement artifact can be distinguished effectively. Furthermore, the effectiveness of the proposed approach is verified by signal-to-noise ratio, energy ratio, cross correlation coefficient and power spectrum. This method can eliminate not only movement artifact, but also baseline wander and high-frequency noise. Thus, it provides an effective approach for the calculation of pulse rate and blood oxygen saturation.

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.

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.

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 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.

Ruifeng H.,Xidian University
Fluid Dynamics Research | Year: 2015

In this work, we performed a computational study on the three-dimensional (3D) flow past a rotating wing at a low Reynolds number (Re = 200). The 3D vortical structures and aerodynamic performances of the rotating wing with different aspect ratios and rotating speeds are computed and analyzed. A quasi-steady model is adopted for prediction of aerodynamic performances of the wing, and its applicability is evaluated by the computation. It is found that there exists a periodic vortex shedding pattern at a low rotating speed, while vortices may cluster near the wing when rotating speed is high enough. The wake vortex topology is also affected by the aspect ratio. The current quasi-steady aerodynamic model could only be used for rotating wing aerodynamics at a low rotating speed when regularly periodic vortex shedding exists. © 2015 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

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.

Zhao F.,Xidian University
CAD Computer Aided Design | Year: 2014

An improved meshless density variable approximation is incorporated into the BESO method for topology optimization of continuum structures in this paper. The essential boundary condition is enforced by using the compactly supported radial basis function (CSRBF). The Shepard function is used to create a physically meaningful dual-level density approximation. Numerical examples show that the proposed method is feasible and fidelity for the topology optimization of continuum structures. The common numerical instabilities of the BESO method do not exist in the final results. © 2014 Elsevier Ltd. All rights reserved.

Cao X.,Duke University | Kou W.,Xidian University | Du X.,Northwest Normal University
Information Sciences | Year: 2010

Based on the computational Diffie-Hellman problem, this paper proposes an identity-based authenticated key agreement protocol which removes bilinear pairings. Compared with previous protocols, the new protocol minimizes message exchange time with no extra cost. The protocol provides strong security guarantees including key compromise impersonation resilience, perfect forward secrecy, and master key forward secrecy. A security proof with the modular approach in the modified Bellare-Rogaway model is also provided. © 2010 Elsevier Inc. All rights reserved.

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.

Liu B.,Xidian University
ETRI Journal | Year: 2014

This paper studies a dual-hop multiple-access relay network where two independent source nodes transmit information to a common destination node with the aid of multiple single-antenna amplify-and-forward relays. Each relay node is subject to an individual power constraint. We focus on the design of distributed beamforming schemes for the relays to support the transmission rate requirements of the two sources. To this end, we first characterize the achievable rate region for this network via solving a sequence of corner point optimization problems proposed in this paper. We also develop several low-complexity suboptimal schemes in closed form. Two inner bounds of the achievable rate region are theoretically shown to be approximately optimal in two special scenarios. Finally, numerical results demonstrate the effectiveness of our proposed approaches. © 2014 ETRI.

Yang M.,Hong Kong Polytechnic University | Zhang L.,Hong Kong Polytechnic University | Feng X.,Xidian University | Zhang D.,Hong Kong Polytechnic University
Proceedings of the IEEE International Conference on Computer Vision | Year: 2011

Sparse representation based classification has led to interesting image recognition results, while the dictionary used for sparse coding plays a key role in it. This paper presents a novel dictionary learning (DL) method to improve the pattern classification performance. Based on the Fisher discrimination criterion, a structured dictionary, whose dictionary atoms have correspondence to the class labels, is learned so that the reconstruction error after sparse coding can be used for pattern classification. Meanwhile, the Fisher discrimination criterion is imposed on the coding coefficients so that they have small within-class scatter but big between-class scatter. A new classification scheme associated with the proposed Fisher discrimination DL (FDDL) method is then presented by using both the discriminative information in the reconstruction error and sparse coding coefficients. The proposed FDDL is extensively evaluated on benchmark image databases in comparison with existing sparse representation and DL based classification methods. © 2011 IEEE.

Wu S.-J.,Xidian University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

Developing compressed sensing (CS) theory has been applied in radar imaging by exploiting the inherent sparsity of radar signal. In this paper, we develop a super resolution (SR) algorithm for formatting inverse synthetic aperture radar (ISAR) image with limited pulses. Assuming that the target scattering field follows an identical Laplace probability distribution, the approach converts the SR imaging into a sparsity-driven optimization in Bayesian statistics sense. We also show that improved performance is achieved by taking advantage of the meaningful spatial structure of the scattering field. To well discriminate scattering centers from noise, we use the non-identical Laplace distribution with small scale on signal components and large on noise. A local maximum likelihood estimator combining with bandwidth extrapolation technique is developed to estimate the statistical parameters. Experimental results present advantages of the proposal over conventional imaging methods. © 2011 IEEE.

Wang G.,Xidian University | Chen H.,University of Tokyo
IEEE Transactions on Wireless Communications | Year: 2011

We consider the source localization problem using time-difference-of- arrival (TDOA) measurements in sensor networks. The maximum likelihood (ML) estimation of the source location can be cast as a nonlinear/nonconvex optimization problem, and its global solution is hardly obtained. In this paper, we resort to the Monte Carlo importance sampling (MCIS) technique to find an approximate global solution to this problem. To obtain an efficient importance function that is used in the technique, we construct a Gaussian distribution and choose its probability density function (pdf) as the importance function. In this process, an initial estimate of the source location is required. We reformulate the problem as a nonlinear robust least squares (LS) problem, and relax it as a second-order cone programming (SOCP), the solution of which is used as the initial estimate. Simulation results show that the proposed method can achieve the Cramer-Rao bound (CRB) accuracy and outperforms several existing methods. © 2011 IEEE.

Han R.,Northwestern University | Han B.,Northwestern University | Wang D.H.,Northwestern University | Li C.,Xidian University
Applied Physics Letters | Year: 2011

Noncontact temperature measurements based on Raman scattering were performed on 4H-SiC with hexagonal defects. These measurements show that the four-phonon process makes a greater contribution to the E2(TO) mode than to the E1(TO) mode. The longer lifetimes of E2(TO) and E1(TO) phonons in hexagonal defects demonstrate that there are fewer possible decay channels than in the defect free zone. The absence of electronic Raman peaks in the hexagonal defects suggests that hexagonal defects seriously limit the uniformity of the nitrogen distribution. The intensity of electronic Raman spectra is related to the density of neutral nitrogen atoms. © 2011 American Institute of Physics.

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.

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.

Wang X.-M.,Xidian University
Monthly Notices of the Royal Astronomical Society | Year: 2015

Considering the evaporation cooling of icy particles, we propose a mechanism for planetesimal formation in an evolving protoplanetary disc. Because of gas drag, icy particles undergo orbital decay. As these particles cross the snow line, they begin to evaporate. When they move to an enough hot region, a positive feedback process will begin near the evaporation front. Because of rapid evaporation near the front, particles rapidly cool the surrounding gas. The disc structure near the front is significantly changed after enough particles evaporate there. A prominent feature is the pressure gradient becomes shallow. Subsequent inward moving particles will pile up near the front. As they evaporate, the pressure gradient becomes shallower and a pressure maximum forms finally. Particles will pile up there further. When there are enough particles near the evaporation front, planetesimals can form through gravitational instability. In the calculation, we consider the total gas disc evolution, the water vapour disc evolution, the icy particle disc evolution, and interactions among the three discs. It is shown that, for an icy particle disc initially made up of metre-sized particles, in ~102 yr, the particle density near the evaporation front will become high enough to form planetesimals, while only a small fraction of the icy particle disc mass is consumed. In addition, we study the effects of initial particle radius, the water-to-gas ratio, the disc viscosity, and the initial position of the snow line. © 2015 The Authors.

Guo J.,Xidian University | Wu D.,Weinan Normal University
Electronics Letters | Year: 2014

Based on the low rank representation (LRR) and the sparse representation (SR), a composite LRR with SR graph LRRSR for semi-supervised label propagation is proposed. The LRRSR aims to capture both the global structure of the data by a low rank constraint and the local structure of the data by a sparse constraint simultaneously. A composite framework is applied to fuse the two graphs. Then, a label propagation framework is used to transmit the labels from the labelled samples to the unlabelled samples. It is applied on several face image datasets and the experimental results demonstrate its good performance for face classification with a limited number of labelled samples. © The Institution of Engineering and Technology 2014.

Hu H.,Xidian University | Liu Y.,Nanyang Technological University
IEEE Transactions on Automation Science and Engineering | Year: 2014

In the framework of automated manufacturing systems (AMS), Petri nets are widely used to model, analyze, and control them. Resolving deadlocks is of paramount significance because their emergence may likely zero a systems throughput, if not necessarily. Supervisory control technique is the most widely adopted method to resolve them. A control policy can be converted into satisfying a set of inequalities, each of which corresponds to a siphon in a Petri net structure. The number of siphons can be exponential in the worst case, so does the number of inequalities. Taking into account the independent and dependent inequalities, this paper proposes a method to remove all the dependent inequalities, while preserving only the independent ones. This method can significantly reduce the size of a supervisory controller. Examples are presented to illustrate the effectiveness and efficiency of this method. © 2013 IEEE.

Wang W.-J.,Xidian University
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2012

A new method of discriminant feature extraction, called Class Preserving Projection (CPP), is proposed from the point view of class relation of pairwise samples. Compared to LDA, CPP has the following two advantages. One is that the optimal subspace dimension is not restricted to the number of categories of samples, and the other is that computational complexity is lower. Experiments are performed on gene expression data for sample classification, and the results confirm the effectiveness of the method. Kernel CPP (KCPP) is presented by generalizing CPP to nonlinear space to solve the problem of nonlinear feature extraction, and the experiments on gene expression data verify the feasibility of the method.

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.

Liu W.,National University of Defense Technology | Xie W.,Wuhan Radar Academy | Liu J.,Xidian University | Wang Y.,Wuhan Radar Academy
IEEE Transactions on Signal Processing | Year: 2014

In this two-part paper, we consider the problem of adaptive multidimensional/multichannel signal detection in Gaussian noise with unknown covariance matrix. The test data (primary data) is assumed as a collection of sample vectors, arranged as the columns of a rectangular data array. The rows and columns of the signal matrix are both assumed to lie in known subspaces, but with unknown coordinates. Due to this feature of the signal structure, we name this kind of signal as the double subspace signal. Part I of this paper focuses on the adaptive detection in homogeneous environments, while Part II deals with the adaptive detection in partially homogeneous environments. Precisely, in this part, we derive the generalized likelihood ratio test (GLRT), Rao test, Wald test, as well as their two-step variations, in homogeneous environments. Three types of spectral norm tests (SNTs) are also introduced. All these detectors are shown to possess the constant false alarm rate (CFAR) property. Moreover, we discuss the differences between them and show how they work. Another contribution is that we investigate various special cases of these detectors. Remarkably, some of them are well-known existing detectors, while some others are still new. At the stage of performance evaluation, conducted by Monte Carlo simulations, both matched and mismatched signals are dealt with. For each case, more than one scenario is considered. © 1991-2012 IEEE.

Liu W.,National University of Defense Technology | Xie W.,Wuhan Radar Academy | Liu J.,Xidian University | Wang Y.,Wuhan Radar Academy
IEEE Transactions on Signal Processing | Year: 2014

In this part of the paper, we continue to study the problem of detecting a double subspace signal in Gaussian noise. Precisely, we address the detection problem in partially homogeneous environments, where the primary and secondary data share the same covariance matrix up to an unknown scaling factor. We derive the generalized likelihood ratio test (GLRT), Rao test, Wald test, and their two-step versions. We also introduce three spectral norm tests (SNTs). All these detectors possess the constant false alarm rate (CFAR) property. Moreover, various kinds of special cases of these detectors are given. At the stage of performance evaluation, we consider two cases. One is the case of no signal mismatch. The other is more general, namely, the case of signal mismatch, including the column-space signal mismatch and row-space signal mismatch. © 1991-2012 IEEE.

Xu J.,CAS Shanghai Institute of Microsystem and Information Technology | Wang J.,University of Electronic Science and Technology of China | Zhu Y.,Wuhan University of Technology | Yang Y.,Nanjing Southeast University | And 3 more authors.
IEEE Communications Magazine | Year: 2014

The fifth generation mobile networks will be developed to improve area spectral and energy efficiency, and provide uniform user experience. Hyper-dense small cell deployment can move devices closer to the wireless network and satisfy 5G system requirements. The main challenge of this network deployment results from the random deployment, dynamic on-off, flexible connection to cellular core networks, and flat system architecture of 5G systems. Therefore, conventional network planning and radio resource management, which depend on a central control node, cannot be applied to small cell networks. In this article some cooperative distributed radio resource management algorithms for time synchronization, carrier selection, and power control are discussed for hyper-dense small cell deployment. © 2014 IEEE.

In this letter, a low-complexity detector, called ordered nearest neighbor search (NNS) minimum mean square error (MMSE) detector, is proposed for the spatial modulation multiple-access channel with a large number of receive antennas. In the proposed detector, the antenna index is first determined based on the channel direction information, and then, the modulation signal is recovered by the MMSE detector. Furthermore, to improve the separable detection performance, an ordered candidate list of the antenna index is acquired through NNS. Simulation results show that the proposed detector approaches the interference-free performance with very low complexity. © 1997-2012 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.

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.

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.

Li S.,Xidian University
Xi'an Dianzi Keji Daxue Xuebao/Journal of Xidian University | Year: 2013

The slider-crank mechanism is a transmission mechanism extensively used in engineering practice. It is necessary to use the control system for getting a satisfactory trajectory. So the mechanism design is composed of two parts, structural design and control design. These two parts impact each other and are tightly coupled, and the separate design can not obtain the best performance. Hence integrated design is imperative. By making use of the Lyapunov function, an integrated design considering stability is proposed in this paper, seeing that stability is the most basic requirements of a closed-loop system. Simulation results show that this method can effectively carry out the mechanism design, reduce the body weight, optimize mechanism performance and save the design cost simultaneously.

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.

Chen W.,Xidian University
Journal of Systems Engineering and Electronics | Year: 2010

For the first time, an adaptive backstepping neural network control approach is extended to a class of stochastic nonlinear output-feedback systems. Different from the existing results, the nonlinear terms are assumed to be completely unknown and only a neural network is employed to compensate for all unknown nonlinear functions so that the controller design is more simplified. Based on stochastic LaSalle theorem, the resulted closed-loop system is proved to be globally asymptotically stable in probability. The simulation results further verify the effectiveness of the control scheme.

Wang F.,PLA Fourth Military Medical University | Wang F.,Xidian University | Niu G.,U.S. National Institutes of Health | Chen X.,U.S. National Institutes of Health | Cao F.,PLA Fourth Military Medical University
European Journal of Nuclear Medicine and Molecular Imaging | Year: 2011

MicroRNAs (miRNAs) are a novel class of small noncoding RNAs that regulate gene expression by targeting mRNAs for either cleavage or translational repression. They have been shown to play important roles in a broad range of biological processes including development, cellular differentiation, proliferation and apoptosis. Conventional detection methods, such as northern blot, realtime PCR or microarray, have been used to assess miRNA expression. However, these techniques require the fixation or lysis of cells, and thus cannot be used to study the dynamic function of miRNAs in living cells. Recent remarkable advances in molecular imaging techniques have provided the capability of noninvasive repeated quantitative imaging of tumour or stem cells in living animals. The current brief discussion focuses on the reporter and fluorescent beacon imaging approaches to visualize miRNA expression in living subjects. © Springer-Verlag (outside the USA) 2011.

Zhang W.,North China Electrical Power University | Zeng D.,North China Electrical Power University | Qu S.,Xidian University
IET Control Theory and Applications | Year: 2010

This study investigates consensus of high-order multi-agent systems. A new dynamic neighbour-based protocol is proposed that only uses the relative information of the first states of agents, extending second-order protocols from the literature. Sufficient conditions are derived to make all agents reach consensus. Finally, simulation results are included to show the effectiveness of the obtained results. © 2010 The Institution of Engineering and Technology.

Lin Z.-Z.,Xidian University
Modern Physics Letters B | Year: 2015

By a tight-binding model, the interaction between linear atomic C chains (LACCs) and short laser pulses was investigated. LACCs were proposed to be used as a medium of laser whose wavelength can be continuously tuned in a range of 321-785nm. This data should be more accurate than the previous result [Europhys. Lett. 97 (2012) 27006] because pure density functional theory calculation always underestimates the band gap. According to the tight-binding model, the lifetime of conduction band (CB) bottom is about 1.9-2.3ns. The electrons pumped into the CB will quickly fall to the band bottom in a time of ps due to electron-phonon interactions. The above results indicate that LACCs are suitable for laser medium. By ω + 2ω dichromatic laser pulses, photocurrents can be generated in LACCs, which can be applied as light-controlled signals. © 2015 World Scientific Publishing Company.

Abstract At present, Pt nanoparticle catalysts in fuel cells suffer from aggregation and loss of chemical activity. In this work, graphdiyne, which has natural porous structure, was proposed as substrate with high adsorption ability to stabilize Pt nanoparticles. Using multiscale calculations by ab initio method and the ReaxFF potential, geometry optimizations, molecular dynamics simulations, Metropolis Monte Carlo simulations and minimum energy paths calculations were performed to investigate the adsorption energy and the rates of desorption and migration of Pt nanoparticles on graphdiyne and graphene. According to the comparison between graphdiyne and graphene, it was found that the high adsorption ability of graphdiyne can avoid Pt nanoparticle migration and aggregation on substrate. Then, simulations indicated the potential catalytic ability of graphdiyne-Pt-nanoparticle system to the oxygen reduction reaction in fuel cells. In summary, graphdiyne should be an excellent material to replace graphite or amorphous carbon matrix for stabilizing Pt nanoparticle catalysts. © 2015 Elsevier Ltd. All rights reserved.

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.

Zhang Z.,Xidian University | Zhang Z.,Boston University | Torr P.H.S.,University of Oxford
IEEE Transactions on Pattern Analysis and Machine Intelligence | Year: 2016

Object proposal algorithms have shown great promise as a first step for object recognition and detection. Good object proposal generation algorithms require high object detection recall rate as well as low computational cost, because generating object proposals is usually utilized as a preprocessing step. The problem of how to accelerate the object proposal generation and evaluation process without decreasing recall is thus of great interest. In this paper, we propose a new object proposal generation method using two-stage cascade support vector machines (SVMs), where in the first stage linear filters are learned for predefined quantized scales/aspect-ratios independently, and in the second stage a global linear classifier is learned across all the quantized scales/aspect-ratios for calibration, so that all the windows from the first stage can be compared properly. The windows with highest scores from the second stage are kept as inputs to our new efficient proposal calibration algorithm to improve their localization quality significantly, resulting in our final object proposals. We explain our scale/aspect-ratio quantization scheme, and investigate the effects of combinations of ell-1 and ell-2 regularizers in cascade SVMs with/without ranking constraints in learning. Comprehensive experiments on VOC2007 dataset are conducted, and our method is comparable with the current state-of-the-art methods with much better computational efficiency. © 1979-2012 IEEE.

Xing K.,Xian Jiaotong University | Zhou M.,New Jersey Institute of Technology | Zhou M.,Xidian University | Wang F.,Xian 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.

Huang C.-T.,Georgia Institute of Technology | Huang C.-T.,National Tsing Hua University | Song J.,Georgia Institute of Technology | Lee W.-F.,National Tsing Hua University | And 5 more authors.
Journal of the American Chemical Society | Year: 2010

Three-fold symmetrically distributed GaN nanowire (NW) arrays have been epitaxially grown on GaN/sapphire substrates. The GaN NW possesses a triangular cross section enclosed by (0001), (2112), and (2112) planes, and the angle between the GaN NW and the substrate surface is ∼62°. The GaN NW arrays produce negative output voltage pulses when scanned by a conductive atomic force microscope in contact mode. The average of piezoelectric output voltage was about -20 mV, while 5-10% of the NWs had piezoelectric output voltages exceeding -(0.15-0.35) V. The GaN NW arrays are highly stable and highly tolerate to moisture in the atmosphere. The GaN NW arrays demonstrate an outstanding potential to be utilized for piezoelectric energy generation with a performance probably better than that of ZnO NWs. © 2010 American Chemical Society.

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.

Hu H.,Xidian University | Zhou M.,New Jersey Institute of Technology
IEEE Transactions on Control Systems Technology | Year: 2015

In the context of automated manufacturing systems (AMSs), Petri nets are widely adopted to solve the modeling, analysis, and control problems. So far, nearly all known approaches to liveness-enforcing supervisory control study AMSs with flexible routes, whereas little work investigates the ones with synchronization operations. Compared with flexibility, synchronization allows the disassembly and assembly operations that correspond to splitting to and merging from different subprocesses, respectively. Such structures bring difficulties to establish a liveness condition of the Petri net model of AMSs. In this paper, we propose a novel class of systems, which can well deal with these features so as to facilitate the investigation of such complex systems. Using structural analysis, we show that their liveness can be attributed to deadlock freeness, which is much easier to analyze, detect, and control by synthesizing a proper supervisory controller. Furthermore, a set of mathematical formulations is proposed to describe and extract the corresponding deadlocks. This facilitates the synthesis of liveness enforcing supervisors as it avoids the consideration of deadlock-free but nonlive scenarios. The effectiveness and efficiency of this new method is shown by AMS examples. © 1993-2012 IEEE.

Xiao J.-K.,Xidian University | Zhu Y.-F.,China Telecom
AEU - International Journal of Electronics and Communications | Year: 2014

In this paper, inner T-shaped defected microstrip structure (DMS) is studied, and new bandstop filters with a single band, dual-band and tri-band are developed. The new designs have adjustable multi-band operation and simple circuit topologies, and the symmetrical periodic T-shaped DMS introduces transmission zeros which improve the filter frequency selectivity greatly. The circuit sizes are also reduced because of the inner T-shaped DMS introduces more resonances in a frequency range of 10 GHz but without the requirement of certain coupled lines or resonators. The dual-band and tri-band designs are demonstrated by measurement. © 2013 Elsevier GmbH.

Wang Z.,Shanghai JiaoTong University | Wang Z.,Xidian University | Chen W.,Shanghai JiaoTong University | Chen W.,China Mobile | Li J.,University of New South Wales
IEEE Transactions on Vehicular Technology | Year: 2012

We consider a multiple-input-multiple-output (MIMO) relaying broadcast channel in downlink cellular networks, where the base station and the relay stations are both equipped with multiple antennas, and each user terminal has only a single antenna. In practical scenarios, channel estimation is imperfect at the receivers. Aiming to maximize the signal-to-interference noise ratio (SINR), at each user, we develop two robust linear beamforming schemes for the single-relay case and the multirelay case, respectively. The two proposed schemes are based on singular value decomposition (SVD), minimum mean square error (MMSE), and regularized zero forcing (RZF). Simulation results show that the proposed scheme outperforms the conventional schemes with imperfect channel estimation. © 2011 IEEE.

This correspondence points out an error in a critical lemma in Hu et al. (2008). © 2015 Elsevier Ltd.

Zhang W.,Xidian University
Electronics Letters | Year: 2015

Support vector data description (SVDD) is a data description method which gives the target data set a hypersphere-shaped description and can be used for one-class classification or outlier detection. To further improve its performance, a novel SVDD called SVDD+ which introduces the privileged information to the traditional SVDD is proposed. This privileged information, which is ignored by the classical SVDD but often exists in human learning, will optimise the training phase by constructing a set of correcting functions. The performance of SVDD+ on data sets from the UCI machine learning repository and radar emitter recognition is demonstrated. The experimental results indicate the validity and advantage of this method. © The Institution of Engineering and Technology 2015.

Yan Z.,Xidian University | Yan Z.,Aalto University | Chen Y.,Ecole Polytechnique Federale de Lausanne | Shen Y.,Aalto University
Journal of Computer and System Sciences | Year: 2013

A Mobile Ad Hoc Network (MANET) is becoming a practical platform for pervasive social networking. For example, people chat with each other via MANET for instant social activities. How to help mobile users build up trust in pervasive social chatting is becoming an important and interesting issue. By applying a method for usable trust management, we designed PerChatRep, a reputation system for pervasive social chatting based on the result of a need assessment survey. We evaluated the effectiveness and robustness of PerChatRep through simulations. Furthermore, we implemented the system by applying Nokia N900 smart phones as MANET nodes based on a distributed energy-efficient social networking platform. We further conducted a two-session controlled user experiment to investigate the impacts of PerChatRep on mobile users. Results show the usefulness and user acceptance of PerChatRep. © 2012 Elsevier Inc.

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.

Pasalic E.,University of Primorska | Zhang W.G.,Xidian University
Information Processing Letters | Year: 2012

In this article we investigate the possibilities of obtaining multiple output bent functions from certain power polynomials over finite fields. So far multiple output bent functions F:GF(2)n→GF(2)m (where n is even and m≤n/2), for any particular class of Boolean bent functions, has been generated using a suitable collection of m Boolean bent functions so that any nonzero linear combination of these functions is again bent. Here, we take a different approach by deriving these functions directly from the known classes of so-called monomial trace bent functions. We derive a sufficient condition for a bent Boolean function of the form f(x)=Tr1n(λxd) so that the associated mapping F(x)=Trmn(λxd), where F:GF(2)n→GF(2)m, is a multiple output bent function. We consider all the main cases of monomial trace bent functions and specify the restrictions on λ and m that yield multiple output bent functions F(x)=Trmn(λxd). Interestingly enough, in one particular case when n=4r, d=(2r+1)2, a multiple bent function F(x)=Tr2rn(axd) could not be obtained by considering a collection of 2r Boolean bent functions of the form fi(x)=Tr1n(λixd) for some suitable coefficients λi ε GF(2n). © 2012 Elsevier B.V.

Jiang L.,China University of Petroleum - East China | Yin H.,Xidian University
Multidimensional Systems and Signal Processing | Year: 2012

Sparse nonnegative matrix factorizations can be considered as dimension reduction methods that can control the degree of sparseness of basis matrix or coefficient matrix under non-negativity constraints. In this paper, by exploring the sparsity of the basis matrix and the coefficient matrix under certain domains,we propose an alternative iteration approach with l1-norm minimization for face recognition. Moreover, a modified version of linearized Bregman iteration is developed to efficiently solve the proposed minimization problem. Experimental results show that new algorithm is promising in terms of detection accuracy, computational efficiency. © Springer Science+Business Media, LLC 2011.

Wei H.-Y.,Taiyuan University of Technology | Wu Z.-S.,Xidian University | Ma Q.-L.,Taiyuan University of Technology
Progress in Electromagnetics Research | Year: 2010

Based on the altitude-dependent model of ITU-R slant atmospheric turbulence structure constant, the log-amplitude variance of laser beam propagation on the slant path through turbulent atmosphere is obtained with transmitter and receiver parameters and can be degenerated to the result of the horizontal path with atmospheric structure constant as a fixed value. These expressions are convenient tools for beam-wave analysis. Finally, we apply the ITU-R turbulence structure constant model to calculate collimated, divergent and convergent beam log-amplitude variance. The numerical conclusions indicate the log-amplitude variance of laser beam propagation on slant path is generally smaller than those on horizontal path.

Shi Y.,Xidian University | Chan C.H.,City University of Hong Kong
IEEE Transactions on Antennas and Propagation | Year: 2010

The difficulty for the solution of full-wave electromagnetic problems using multilevel Green's function interpolation method (MLGFIM) lies in applying interpolating approaches to efficiently and accurately approximate Green's function with rapidly changing phase term. We compare various interpolating schemes when radial basis function (RBF) is employed for the interpolation of scattered data of Green's function. We show that the infinitely smooth Gaussian (GA) RBF has the best interpolation accuracy. In order to improve the interpolation efficiency, a new kind of staggered Tartan grid is proposed. A good calculation method for the shape parameter in GA RBF is given to solve its sensitivity to the group size and the number of interpolation points. Based on the analysis of variation of the number of interpolation points with electric length of the group, adaptive choice of the types of interpolation functions and interpolation points are employed. Numerical examples show that the computational efficiency of this new interpolation scheme is much improved over the previously reported ones. © 2006 IEEE.

Bai X.,Xidian University
IEEE Transactions on Aerospace and Electronic Systems | Year: 2014

This paper derives the signal model for high-resolution radar imaging of two canonical rotation-symmetric targets in space, i.e., the smooth cone and the smooth cylinder, according to their electromagnetic (EM) modeling in the high-frequency regime and their specific rotation motion. Then, a method based on the complex generalized Radon transform is proposed for image formation and motion parameter estimation. Imaging results of dynamic EM echoes have proved the validity of the proposed method. © 2014 IEEE.

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.

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.

Qin G.,Tongji University | Qin G.,Xidian University | Zhao X.-M.,Tongji University
Journal of Theoretical Biology | Year: 2014

The disease biomarkers can help make accurate diagnosis and therefore give appropriate interventions. In the past years, the accumulation of various kinds of 'omics' data, e.g. genomics and transcriptomics, makes it possible to identify disease biomarkers in a more efficient way. In particular, the molecular networks that describe the functional relationships among molecules enable the identification of disease biomarkers from a systematic perspective. In this paper, we surveyed the recent progress on the computational approaches that have been developed to identify disease biomarkers based on molecular networks. In addition, we introduced the popular resources about human interactomes and regulatomes as well as human diseasomes, whose availability makes it possible to predict the disease biomarkers with the utility of networks. © 2014 Elsevier Ltd.

One-dimensional (1D) TiO 2 nanowire arrays are fabricated on transparent conducting substrates via a low temperature hydrothermal route for application in dye-sensitized solar cells (DSSCs). The as-prepared sample on fluorine-doped tin oxide (FTO) substrate is found to be single-crystalline rutile TiO 2 structures from X-ray and electron diffractions. The length and diameter of the nanowires depend mainly on the growth time and temperature. With increasing the reaction time, the growth rate becomes slower and the interface adhesion between the growth nanowires and the substrate becomes weaker. In the same time the adjacent nanowires aggregate to larger the apparent diameter of the nanowire making the gaps among the nanowires to disappear at last. The nanowires exhibit flower-like morphology on the non-conducting surface of FTO substrate. By using TiO 2 nanowire arrays with 2 μm long on FTO substrate as the photoanode in DSSCs, an overall light conversion efficiency of 1.58% is achieved with an open circuit voltage of 0.714 V, a short circuit current density of 4.68 mA cm ?2, and a fill factor of 0.472. © 2011 American Scientific Publishers. All rights reserved.

Zhao X.,Xidian University
IEEE Communications Letters | Year: 2012

In a recent letter, Trullols-Cruces et al. derived the exact decoding probability P ns(K,N) that a receiver node obtained N linearly independent coded packets among K (K N) received coded packets, when the source node uses a random linear coding scheme over a Galois Field GF(q). They discussed P ns(K,N) both in the case of the source node sending the random linear combination of the original packets, including all-zero combinations, as well as the case of excluding all-zero combinations. However, their derivations are a bit complicated. In this note, we demonstrate simple derivations of the exact decoding probability P ns(K,N) in both cases. Furthermore, we point out that there is a more succinct expression of P ns(K,N) for the latter case. © 2012 IEEE.

Luo F.,Xidian University | Yuan X.,Duke University
Eurasip Journal on Advances in Signal Processing | Year: 2012

A new configuration of sparse array is proposed in this article to estimate the direction-of-arrivals (DOAs) and polarizations of multiple sources. This constrained sparse array is composed of a dipole-triad, a loop-triad, and a single antenna, which can be a dipole, a loop, or a scalar-sensor. These three units comprise a triangular geometry in the space. This geometry creatively synergizes the conventional interferometry method based on the spatial phase-delay across displaced antennas, and the "vector-cross-product" based on Poynting-vector estimator to enhance the DOA estimation accuracy. The investigated algorithm based on this configuration adopts the "vectorcross-product" DOA estimator to provide the coarse estimate and then derives the fine estimate by extracting the inter-sensor phase factors in the sparse array. Following this, the disambiguation approach is adapted to derive the unambiguous estimate, and this estimate is also fine in estimation resolution. The proposed configuration can extend the array aperture and also reduce the mutual coupling. The significant performance of the proposed sparse array composition is demonstrated by Monte Carlo simulations when the inter-sensor spacing far exceeds a half-wavelength. © 2012 Luo and Yuan.

Yang F.,Xidian University | Wan S.,Northwestern Polytechnical University
IEEE Communications Magazine | Year: 2012

Bitstream-based methods are intuitively suited for quality assessment of networked video services, and are currently under intense investigations in terms of research and standardization activities. This article examines the factors that may affect the quality of the networked video, and reviews the state-of-the-art techniques as well as standardization progress in bitstreambased video quality assessment. According to different levels of access to the bitstream, three types of models are described and compared: the parametric, packet layer, and bitstream-layer models. © 1979-2012 IEEE.

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.

Lin Z.-Z.,Xidian University | Chen X.,Xian 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.

Ji J.,Xidian University
IET Image Processing | Year: 2012

This study proposes a method that improves the robustness of independent component analysis (ICA) by adding outlier rejection rule for solving synthetic aperture radar (SAR) image analysis problems. Since the noise in SAR images is multiplicative, the applicability of ICA is seriously reduced. The proposed robust approach includes three procedures. After a pre-processing stage of principal component analysis, the authors remove outliers by applying outlier rejection rule for multivariate data. Then the ICA method is applied on the clean data set. Its applications in SAR are discussed. The results show the potential usage of this robust approach in SAR image processing problems. © 2012 The Institution of Engineering and Technology.

Fan K.,Xidian University | Fan K.,University of Alberta | Pedrycz W.,University of Alberta
Physica A: Statistical Mechanics and its Applications | Year: 2015

Understanding the emergence and diffusion of extreme opinions becomes important to our globalized society. In this study, we propose a social judgment based opinion (SJBO) dynamics model, which incorporates both the compromise between similar opinions and the repulsion between discrepant opinions, to study the occurrence and spread of extremism in two different scenarios. The first concerns a situation in which individuals interact with each other through their inner opinions, while the second involves a case that each individual updates his inner opinion and choice via observing his neighbor's choice. The simulation results show that, in the first scenario, a critical uncertainty level is present, at which the size of extremists can be maximized. Increasing or decreasing the uncertainty level from the critical value can diminish or even eliminate the extremists. In the second scenario, high uncertainty level tends to promote the development of extremists. However, the extremism can be contained or even avoided if the influence scope of silencers is large enough. In both scenarios, a large level of tolerance can help to reduce extremists as well. © 2015 Elsevier B.V. All rights reserved.

Wang H.,Changan University | Wang B.,Xidian University
Guangxue Xuebao/Acta Optica Sinica | Year: 2012

In order to reduce the measurement error caused by camera radial distortion in measurement system based on image, a new distortion calibration method is designed, resorting to characteristic concentric circles target. A character target rode on a two-dimensional fine platform is situated in a known position of the object side which is vertical to the optical axis, then the target images are collected and processed. A least square arithmetic is introduced to compute the fitting radius according to which the characteristic target is moved in a scheduled mode until the radius is maxim or in the demanded range. At the very time the center of the concentric circles is the camera distortion center, the coefficients of the distortion polynomial are gotten recurring to relation of arithmetical radius and imaging model radius of the camera. To find the distortion center coordinate rapidly, a coordinate alternating optimization arithmetic is applied. Experimental results show that the precision of the camera radial distortion center location demarcating can reach 0.6 pixel, and the repeated error of significant figures for polynomial coefficients is less than 0.02, and all can be realized with one character target. The distorted image can be corrected perfectly.

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.

Zhang X.,Xian University of Architecture and Technology | Gao X.,Xidian University
Engineering Applications of Artificial Intelligence | Year: 2012

This paper presents a novel framework for microcalcification clusters (MCs) detection in mammograms. The proposed framework has three main parts: (1) first, MCs are enhanced by using a simple-but-effective artifact removal filter and a well-designed high-pass filter; (2) thereafter, subspace learning algorithms can be embedded into this framework for subspace (feature) selection of each image block to be handled; and (3) finally, in the resulted subspaces, the MCs detection procedure is formulated as a supervised learning and classification problem, and in this work, the twin support vector machine (TWSVM) is developed in decision-making of MCs detection. A large number of experiments are carried out to evaluate and compare the MCs detection approaches, and the effectiveness of the proposed framework is well demonstrated. © 2012 Elsevier Ltd. 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.

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.

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.

Yang D.,Xian University of Technology | Wang L.,Xian University of Technology | Hei X.,Xian University of Technology | Gong M.,Xidian University
Applied Soft Computing Journal | Year: 2014

Artificial immune system (AIS) has been proven effective for pattern classification by its characteristics of learning and adaptability from the vertebrate immune system. However, little focus has been placed on the synthetic aperture radar (SAR) image segmentation by AIS. In this paper, we present an efficient automatic framework in AIS for SAR image segmentation. It aims at simultaneously solving the following three different crucial issues: (1) the automatic ability of searching true number of land-cover in SAR images; (2) the objective functions in guiding the segmentation of the images with complicated multiplicative noises; and (3) reduction of the computational complexity of segmenting SAR images with large sizes. By the proposed framework here, it can mitigate the above difficulties to a certain degree. Furthermore, a reasonable spatial filtering and watershed transformation are employed in the initial stage of the framework, and then a novel clustering index in Gaussian kernel is designed to lead the searching process, which is beneficial to find the partitions for the clustering problem with highly overlapping and contaminating samples. Besides, we also propose an efficient computing paradigm in AIS with variable length of chromosomes to search the optimal partitions of SAR images, which can find the optimal numbers of clusters automatically. Finally, in order to speed up the segmentation process of SAR image, we employ the histogram statistics to implement the pixels partition; therefore, the segmenting time is dependent on the small number of gray-levels, not the great amounts of whole image pixels. To test the segmentation performances of the proposed algorithm, a detailed experimental analysis was conducted on two simulated SAR images and four complicated real ones. Other four state-of-the-art image segmentation methods are employed for comparison, which are genetic clustering by variable string length encoding (VGA), fast generalized fuzzy C-means clustering (FGFCM), fuzzy local information C-means clustering algorithm (FLICM) and graph partitioning method: spectral clustering ensemble (SCE). © 2013 Elsevier B.V.

Cai N.,Xidian University
IEEE Transactions on Information Theory | Year: 2013

In this paper, we extend the localized error correction code introduced by L. A. Bassalygo and coworkers from Hamming space to projective space. For constant dimensional localized error correction codes in projective space, we have a lower bound and an upper bound of the capacity, which are asymptotically tight when z< x≤ n-z2, where x , z, and n are dimensions of codewords, error configurations, and the ground space, respectively. We determine the capacity of nonconstant dimensional localized error correction codes when z < n 3. © 1963-2012 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