Jun 2008, Volume 3 Issue 2
    

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  • XIA Chengyi, LIU Zhongxin, CHEN Zengqiang, YUAN Zhuzhi, XIA Chengyi, SUN Shiwen
    An improved susceptible-infected-susceptible (SIS) model in the local-world evolving network model is presented to study the epidemic spreading behavior with time delay, which is added into the infected phase. The local-world evolving model displays a transition from the exponential network to the scale-free network with respect to the degree distribution. Two typical delay regimes, i.e., uniform and degree-dependent delays are incorporated into the SIS epidemic model to investigate the epidemic infection processes in the local-world network model. The results indicate that the infection delay will promote the epidemic outbreaks, increase the prevalence and reduce the critical threshold of epidemic spreading. It is also found that local-world size M will considerably influence the epidemic spreading behavior with time delay in the local-world network through large-scale numerical simulations. Simulation results are also of relevance to fight epidemic outbreaks.
  • ZHONG Shunshi, LIANG Xianling, YAN Xiaorong
    Recent developments of the ultra-wideband (UWB) planar antennas are reviewed, where the progress in UWB plate monopole antennas, UWB printed monopole antennas and the UWB printed slot antennas is introduced and compared. In addition, the UWB printed antennas with the band-notched functions are also presented.
  • ZHANG Yanyan, TAO Xiaofeng, ZHU Xiaoxuan, ZHANG Ping, TANG Lisha
    Through analyzing the theoretical spreading principle, it has been proved in this paper that the benefit of pseudo-orthogonal carrier interferometry (PO-CI) spreading code is not supported when complex signal modulation (e.g., quadrature phase-shift keying (QPSK) and quadrature amplitude modulation (QAM)) types are employed. On this basis, a novel and feasible structure for this problem is brought forward. Within the structure mentioned, instead of complex modulation patterns, pulse amplitude modulation (PAM) combined with PO-CI spreading code is utilized. This allows us to maintain the throughput increase of a multi-carrier code division multiple access (MC-CDMA) system with minimal loss in performance and no bandwidth expansion.
  • SHAN Linwei, YUAN Jian, REN Yong, SHAN Xiuming
    To deal with long probing delay and inaccurate probing results in the endpoint admission control method, a joint local and end-to-end admission control algorithm is proposed, which introduces local probing of access network besides end-to-end probing. Through local probing, the algorithm accurately estimated the resource status of the access network. Simulation shows that this algorithm can improve admission control performance and reduce users’ average waiting time when the access network is heavily loaded.
  • DING Zhijun, PAN Meiqin, JIANG Changjun, HAN Yaojun
    A series of Petri net-based definitions were formulated for describing four types of structural errors in a rule-based system (RBS), including inconsistency, incompleteness, redundancy and circularity. A marked ?-Petri net model of acyclic RBS was constructed. Then, its reachability tree was generated to record all reachable relations between propositions in RBS. Moreover, a backward reasoning forest of a reachable marking was generated for explicitly representing reachable paths in RBS. Finally, a set of theorems and algorithms were provided to analyze and check structural errors. The usability of the research results presented in this paper was illustrated by an example.
  • ZHANG Zhefei, ZHENG Qinghua, GUAN Xiaohong, WANG Qing, WANG Tuo, GUAN Xiaohong
    SQL injection poses a major threat to the application level security of the database and there is no systematic solution to these attacks. Different from traditional run time security strategies such as IDS and firewall, this paper focuses on the solution at the outset; it presents a method to find vulnerabilities by analyzing the source codes. The concept of validated tree is developed to track variables referenced by database operations in scripts. By checking whether these variables are influenced by outside inputs, the database operations are proved to be secure or not. This method has advantages of high accuracy and efficiency as well as low costs, and it is universal to any type of web application platforms. It is implemented by the software code vulnerabilities of SQL injection detector (CVSID). The validity and efficiency are demonstrated with an example.
  • YANG Bo, YANG Yixian, HU Zhengming, NIU Xinxin, XIAO Zibi
    Based on Chameleon Hash and D. Boneh’s one round multi-party key agreement protocol, this paper proposes a multi-designated verifiers signature scheme. In this scheme only the verifiers designated by the signer can independently verify the signature. And no one else other than the designated person can be convinced by this signature even if one of the designated verifiers reveals the secret value. The analysis of the proposed scheme shows that it satisfies non-transferability, unforgeability and privacy of the signer’s identity and has to low computational cost.
  • SONG Jiaxing, LIN Chuang, LIU Weidong, CHEN Shaoyu
    A peer-to-peer hierarchical replica location mechanism (PRLM) was designed for data grids to provide better load balancing capability and scalability. Global replica indexes of the PRLM are organized based on even distributed Chord (ED-Chord) structure. The locality can optimize queries on local replica indexes of virtual organizations. ED-Chord protocol collects the node identifiers information using a distributed method and assigns optimal identifiers for new nodes to make them more uniformly distributed in the entire identifier space. Theoretical analysis and simulations show that PRLM provides good performance, scalability and load balancing capability for replica location in data grids.
  • ZHOU Jianxiong, SHI Zhiguang, FU Qiang
    A novel scheme for extracting the global scattering center model of radar targets is proposed in this paper. The 2D/3D scattering center models can be reconstructed based on the wideband measurements at different viewing angles. The sphere spreading of the 1D scattering center projections is exploited. The 1D–2D/3D scatterer map (OTSM) is designed to manifest the high dimensional scattering characteristic of radar targets. The Hough transform and the least squares method are used to extract the stable scattering centers and their scattering coefficients. This modeling method does not need a high density of the spatial grid, which greatly cuts down the necessary original data. The model built in this way describes the stable point scattering mechanisms in a large spatial extent and can be extrapolated to other frequencies in the optical region. Examples verify the validity of both the model and the method.
  • LU Qinghua, ZHANG Xianmin, LU Qinghua
    A multi-image wavelet transform motion estimation algorithm based on gradient methods is presented by using the characteristic of wavelet transform. In this algorithm, the accuracy can be improved greatly using data in many images to measure motions between two images. In combination with the reliability measure for constraints function, the reliable data constraints of the images were decomposed with multi-level simultaneous wavelet transform rather than the traditional coarse-to-fine approach. Compared with conventional methods, this motion measurement algorithm based on multi-level simultaneous wavelet transform avoids propagating errors between the decomposed levels. Experimental simulations show that the implementation of this algorithm is simple, and the measurement accuracy is improved.
  • WO Yan, HAN Guoqiang
    This paper proposes a technique of image content authentication based on the Laplacian Pyramid to verify the authenticity of image content. First, the image is decomposed into Laplacian Pyramid before the transformation. Next, the smooth and detail properties of the original image are analyzed according to the Laplacian Pyramid, and the properties are classified and encoded to get the corresponding characteristic values. Then, the signature derived from the encrypted characteristic values is embedded in the original image as a watermark. After the reception, the characteristic values of the received image are compared with the watermark drawn out from the image. The algorithm automatically identifies whether the content is tampered by means of morphologic filtration. The information of tampered location is p resented at the same time. Experimental results show that the proposed authentication algorithm can effectively detect the event and location when the original image content is tampered. Moreover, it can tolerate some distortions produced by compression, filtration and noise degradation.
  • GUAN Jin‘an, CHEN Yaguang
    Communication signals should be estimated by a single trial in a brain-computer interface. Since the relativity of visual evoked potentials from different sites should be stronger than those of the spontaneous electroencephalogram (EEG), this paper adopted the time-lock averaged signals from multi-channels as features. 200 trials of EEG recordings evoked by target or non-target stimuli were classified by the support vector machine (SVM). Results show that a classification accuracy of higher than 97% can be obtained by merely using the 250–550 ms time section of the averaged signals with channel Cz and Pz as features. It suggests that a possible approach to boost communication speed and simplify the designation of the brain-computer interface (BCI) system is worthy of an attempt in this way.
  • YANG Shuyuan, JIAO Licheng, WANG Min
    In this paper, we propose a new directional multi-resolution ridgelet network (DMRN) based on the ridgelet frame theory, which uses the ridgelet as the activation function in a hidden layer. For the multi-resolution properties of the ridgelet function in the direction besides scale and position, DMRN has great capabilities in catching essential features of direction-rich data. It proves to be able to approximate any multivariate function in a more stable and efficient way, and optimal in approximating functions with spatial inhomogeneities. Besides, using binary ridgelet frame as the mathematical foundation in its construction, DMRN is more flexible with a simple structure. The construction and the learning algorithm of DMRN are given. Its approximation capacity and approximation rate are also analyzed in detail. Possibilities of applications to regression and recognition are included to demonstrate its superiority to other methods and feasibility in practice. Both theory analysis and simulation results prove its high efficiency.
  • DANG Xiaoyan, TANG Kun
    The description precision of an excitation signal greatly influences the quality of reconstructed speech in low bit rate vocoders. To improve the reconstruction quality, the DCT_M model is proposed to express the excitation spectral parameter, which transforms the variable length vector to fixed dimension vector through DCT transformation. It then quantizes the fixed length vector using multi-stage vector quantization. Tests show that the proposed method can keep the shape of the entire spectral envelope and reduce model error thus greatly improve the description precision. Test results in the sine excitation linear prediction (SELP) vocoder show that the DCT_M model can improve the naturalness of reconstructed speech, with subjective test score of 65%.
  • MA Qingliang, HU Changhua
    The design of the gain-scheduled H2/H filter for polytopic discrete-time systems is investigated. By introducing additional slack variables, a new mixed H2/H performance criterion is proposed, which provides a decoupling between the Lyapunov matrix and system matrices. Based on the new performance criterion, a sufficient condition for the existence of the gain-scheduled H2/H filter is derived. Furthermore, the filter design problem is converted into a convex optimization problem with linear matrix inequality (LMI) constraints. Simulation results show the effectiveness of the proposed approach.
  • ZHAO Chunna, XUE Dingyü
    The definitions and properties of widely used fractional-order derivatives are summarized in this paper. The characteristic polynomials of the fractional-order systems are pseudo-polynomials whose powers of the complex variable are non-integers. This kind of systems can be approximated by high-order integer-order systems, and can be analyzed and designed by the sophisticated integer-order systems methodology. A new closed-form algorithm for fractional-order linear differential equations is proposed based on the definitions of fractional-order derivatives, and the effectiveness of the algorithm is illustrated through examples.
  • TILMATINE A., BRAHAMI M., MILOUA F., GOURI R., DASCALESCU L.
    Identification of the optimal operating conditions and evaluation of their robustness are critical issues for industrial processes. A standard procedure, for modelling a laboratory-scale wire-to-cylinder electrostatic precipitator and for guiding the research of the set point, is presented. The procedure consists of formulating a set of recommendations regarding the choice of parameter values for electrostatic precipitation. The experiments were carried out on a laboratory cylindrical precipitator, built by one of the authors, with samples of wood particles. The parameters considered are the applied high voltage U, the air flow F, and the quantity of dust in air m. Several “one-factor-at-a-time” followed by factorial composite design experiments were performed, based on the following three-step strategy: 1) Identify the domain of variation of the variables; 2) Determine the mathematical model of the process outcome; 3) Validation of the mathematical model and optimisation of the process.
  • WU Jun, WU Jun, WU Jian, LI Qiang
    This paper investigates the enhancement of Langmuir and ion-acoustic wave and the acceleration of the electron in collisionless plasma, in the presence of an external transverse field. Based on hydrodynamic equations, an equation formulizing the parametric instability was derived. Furthermore, the formula for ponderomotive force and the expression that describes the electron acceleration were obtained. The results show that Langmuir and ion-acoustic wave are enhanced and the charged particles can be accelerated by the coupling of wave-wave. In addition, it can be concluded that ponderomotive force, due to the coupling of the external field (pump) to the Langmuir wave (ion-acoustic wave), is the driving force to excite the parametric instability and comprises the high- and low-frequency components.
  • GUO Weilian, LIANG Huilai, SONG Ruiliang, ZHANG Shilin, MAO Luhong, HU Liuchang, LI Jianheng, QI Haitao, GUO Weilian, FENG Zhen, TIAN Guoping, SHANG Yuehui, LIU Yongqiang, LI Yali, YUAN Mingwen, LI Xiaobai
    In light of fabricating resonant tunneling diode (RTD), in this paper a GaAs-based resonant tunneling transistor with gate structure (GRTT) has been designed and fabricated successfully. A systematic depiction centers on the designs of material structure, device structure, photolithography mask, fabrication of device and the measurement and analysis of parameters. The fabricated GRTT has a maximum PVCR of 46 and a maximum transconductance of 8 mS. The work lays the foundation for further improvement on the performance and parameters of RTT.
  • WANG Yanqing, PANG Xiumei, JIANG Changsheng
    Based on an appropriate Lyapunov function, this paper analyzes the design of a delay-dependent robust H state feedback control, with a focus on a class of nonlinear uncertainty linear time-delay systems with input delay using linear matrix inequalities. Under the condition that the nonlinear uncertain functions are gain bounded, a sufficient condition dependent on the delays of the state and input is presented for the existence of H controller. The proposed controller not only stabilized closed-loop uncertain systems but also guaranteed a prescribed H norm bound of closed-loop transfer matrix from the disturbance to controlled output. By solving a linear matrix inequation, we can obtain the robust H controller. An example is given to show the effectiveness of the proposed method.
  • GU Danying, YANG Jiwen, ZHANG Weidong
    Based on a linearized TCP/AQM model, a new proportional integral (PI) controller design approach is proposed. This analytical approach applies H optimization and internal model control (IMC) theory to design active queue management (AQM) routers that support transmission control protocol (TCP) flows. The most important feature of the proposed scheme lies in that it can be explicitly tuned with a single parameter for the trade-off between performance and stability of the AQM control system. It is thus flexible and easy to use in design. The proposed method and the designed PI controller are verified and compared with other existing AQM schemes using ns-2 simulator. The results show the advantages of the new PI controller design approach for AQM routers supporting TCP flows.
  • GAO Huisheng, JIN Weiwei, LIU Guang
    The end-to-end delay of protective relaying data flow in a substation was studied by dynamic simulation modeling technology. The distribution characteristics of protective relaying data flow and the constitution of the end-to-end delay of messages were analyzed. The simulation model for digital communication between protective relaying equipment and monitoring equipment of interval layer was suggested. The end-to-end delay of protective relaying data flow in different network configurations was analyzed. It is found that the size and interval of the data frame, utilization of the link background and protocols of higher layer are key factors of real-time performance. Detailed analysis results are presented. A proposal for network configuration is suggested to reduce end-to-end delay of protective relaying data flow.
  • Xiong Zhengye, Tang Qiang, Zhang Chunxiang
    Polycrystal Li2B4O7 (LBO) doped with Cu and In was prepared and then sintered at different temperatures. X-ray diffraction (XRD) was applied to get the parameters of the LBO structure, thermoluminescence (TL) and optically stimulated luminescence (OSL) were measured, and a second-order exponential decay model was fitted to the OSL decay curves. The results indicate that the original number of OSL traps that have captured electrons is linearly related with the sum of TL decay during the OSL process. Mean decay constant of OSL is related to the sintered temperature. The possible reason is that the sintered temperature affects the crystal sizes of the polycrystal, and consequently affects the stimulating light s intensity and the photoionization cross-section of the electrons, which have been captured by the traps.