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Table of Content

    20 August 2007 Volume 34 Issue 4
      
    Original Articles
    Fusion kernel optimization algorithm
    CHEN Bo;LIU Hong-wei;BAO Zheng
    J4. 2007, 34(4):  509-513. 
    Abstract ( 2194 )   PDF (733KB) ( 1873 )   Save
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    A fusion kernel optimization algorithm based on the fusion kernel is presented, which improves the method by Xiong et. al. The proposed method uses a data-dependent kernel to maximize the kernel Fisher criterion, so that the different kernels can be fused. Then the method is employed to optimize the kernel of KPCA and the evaluation of the classification performance based on the toy data and measured radar high range resolution profile (HRRP) data show the greater efficiency of our method.
    Cochannel interference suppression for the ship-based passive synthetic impulse and aperture radar
    ZHANG Ya-bin1;2;CHEN Bo-xiao1;ZHANG Shou-hong1;SHANG Hai-yan1
    J4. 2007, 34(4):  514-517. 
    Abstract ( 3486 )   PDF (904KB) ( 1402 )   Save
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    The power distribution and correlation characteristic of cochannel interference are quantitatively analyzed in the ship-based passive Synthetic Impulse and Aperture Radar(SIAR) scenario. The statistical characteristic of interference at the interested range bin is estimated accurately using echoes from some positive and all negative frequency range bins after stretching with consine weight. Thereafter, the Karhunen-Loeve transformation in the temporal domain is used to the echo at the interested range bin and interference is suppressed before adaptive beamforming provided that its power is stronger than radar echoes. Effectiveness of interference suppression is confirmed by real data.
    Upper bound of sample error probability in quasi-orthogonal time division multiplexing
    SUN En-chang;LI Yu-heng;TIAN Bin;YI Ke-chu
    J4. 2007, 34(4):  518-520. 
    Abstract ( 1939 )   PDF (476KB) ( 1138 )   Save
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    Aiming at the deficiencies of sensitivity to time offset in a quasi-orthogonal time division multiplexing (QOTDM) system, this paper derives a formula for the sample error probability based on the separable features of the joint probability density function of independent variables, due to the statistical independence of samples and noise in the QOTDM system. Since the Modified Chernoff bound is significantly tigher than the Chernoff bound, the upper bound of sample error probability is also obtained, thus providing an efficient way to evaluate the sample error performance of the QOTDM systems.
    Full-wave analysis and rigorous design of the waveguide transuerse iris band-pass filter
    ZHAI Yang-wen;SHI Xiao-wei;ZHAO Yong-jiu
    J4. 2007, 34(4):  521-525. 
    Abstract ( 1785 )   PDF (721KB) ( 1268 )   Save
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    The transverse iris of a rectangular waveguide is analyzed by the full wave technique, and combined with the design theory of the filter, the iris is equivalent to an impedance inverter, whose parameter is obtained by full wave analysis, and then a transcendental equation is established by equaling the inverter parameter obtained by the filer synthesis theory with the former. The dimension of the iris can be obtained by solving the equation. The relation between iriss dimension and bandwidth of the band-pass filter is analyzed, which can be of constructive significance in the choice of iris structure for the filter design. Adjustments of the dimension of the designed filter are a voided, and the design is more efficient and more rigorous. Finally, several waveguide band-pass filters are designed based on a half-wave resonance cavity model, and the design values agree well with those of the emulator and experiment.
    MCMC methods based modulation classification over the frequency-selective fading channel
    BAO Dan;WANG Yu-jun;YANG Shao-quan
    J4. 2007, 34(4):  526-531. 
    Abstract ( 2234 )   PDF (772KB) ( 1187 )   Save
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    We propose a novel modulation classifier based on the Markov chain Monte Carlo (MCMC) methods for amplitude-phase modulated signals over the frequency-selective fading channel with multiple unknown parameters such as noise power,carrier frequency and phase offset. The framework for an optimal maximum posterier (MAP) classifier is developed. MCMC methods are employed to generate ergodic random samples from the posterior conditional distributions of the unknown parameters and transmitted symbols, which are derived from the prior distributions of the received signals. Since a close-form expression of the integration of high-dimensional function in the posterior distribution of the modulation can rarely be obtained in the proposed classifier, the Monte Carlo integration is then used to approximate it with these samples. The convergence property and the robust performance of the proposed classifier are then verified via extensive simulations and comparisons with existing approaches.
    Intelligent routing algorithm in direct interconnection networks
    WANG Chang-shan1;NIU Ji-yun1;GU Hua-xi2;KE Chu3
    J4. 2007, 34(4):  532-537. 
    Abstract ( 1932 )   PDF (724KB) ( 1299 )   Save
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    An intelligent routing algorithm FOA (Forward-only Agent) is proposed for the direct interconnection networks. In FOA, only forward agents are used to update the routing information related to their source node while traveling to their destination. A precise model considering various types of delay is used to calculate the trip time taken by the forward agent. Besides, packets are routed randomly based on the goodness of a neighbor which is measured by not only the routing information recorded in the routing table but also the current link condition so as to reach load balance. Simulations were carried out with OPNET software in the k-ary n-cube networks in which virtual cut through switching mechanism is used. The results show that FOA achieves a better performance than other popular algorithms such as DOR, Duato’s algorithm and GAL with a lower delay and a higher throughput.
    Algorithm for quasi-orthogonal hybrid spread-spectrum communication
    ZENG Zhi-bin1;ZHUANG Yi-qi1;XIANG Xin2
    J4. 2007, 34(4):  538-542. 
    Abstract ( 1766 )   PDF (635KB) ( 1186 )   Save
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    A new quasi-orthogonal hybrid spread spectrum communication algorithm and its realized scheme are proposed. The algorithm can achieve BPSK DSSS in the in-phase branch based on the code phase, and the M-ary modulation in the orthogonal branch based on code polority. The system can achieve the starting position of the spread spectrum utilizing the spread spectrum(SS) code in the in-phase branch,and get carrier message with the complementary character of spread spectrum codes in two channels, and it needs no external source of synchronization. The code set of SS codes comes from one SS code by cyclic shifting with the limit of phase area, which is easy to realize. The simulation results demonstrate that the algorithm is effective in improving the utilization ratio of system resources.
    Intra-frame image coding scheme of color video based on the Delaunay triangulation mesh
    JIAO Wei-dong;LU Zhao-yang;HE Hua-jun;GUO Da-bo
    J4. 2007, 34(4):  543-548. 
    Abstract ( 1799 )   PDF (1313KB) ( 1025 )   Save
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    The correlation between the luminance and chrominance components of color video is studied and a new intra-frame coding scheme of color video is proposed based on the DT(Delaunay Triangulation) mesh. In this scheme, the DT image representation is only made for the luminance component and parts mesh nodes of the luminance component Y are used to generate the mesh of chrominance components Cb and Cr via similar transformation. Simulation results show that the proposed method saves almost 30 percent in time while keeping the fine subjective quality for reconstructed image compared with the method by which the DT image representation is made for every component. Moreover, the new method can still provide the better objective quality compared with the intra frame coding method of H.263 and the still texture coding method of MPEG-4.
    Image base features extraction with multi-scale analysis for iris recognition
    LU Chen-hong;LU Zhao-yang
    J4. 2007, 34(4):  549-553. 
    Abstract ( 1943 )   PDF (897KB) ( 1249 )   Save
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    A new iris features extraction method is proposed. The micro-elements of an iris image are analyzed by various image base functions and it is determined that the LoG function is the base function dominating iris image generation. Then the LoG base is used to detect iris minutiae features with multi-scales. Differing from the independent coding method used in traditional multi-scales analysis, the proposed method only codes the responses on the optical scale of each minutiae feature, which is determined by deriving the normalization parameter γ used to normalize the filter responses and computing the local maxima in the scale-space of the normalized detector responses, so that the size of iris feature template is the same as that obtained by single scale analysis. Experimental comparisons show that the proposed method achieves a performance close to that of Daugman’s scheme only using the eighth template size and the Equal Errors of this system is 5% at least lower than that of other recognition methods based on iris minutiae features with multi-scale analysis.
    Suppression of multiple narrowband interferences using kernel methods in DSSS
    SUN Yong-jun;YI Ke-chu
    J4. 2007, 34(4):  554-557. 
    Abstract ( 2060 )   PDF (533KB) ( 1090 )   Save
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    This paper proposes an algorithm for suppressing the multiple narrowband interferences using kernel independent component analysis (KICA) in direct sequence spread spectrum systems. Combining with the kernel methods the algorithm uses canonical correlations in a reproducing kernel Hilbert space (RKHS) as the contrast function. By initializing the demixing matrix using the pseudocode of the expected user, the algorithm realizes the separation of source signals and at the same time the expected user is obtained. As the restrictions are mutually independent of the spread spectrum signal and interferences, which can be easily satisfied in practice, the algorithm is useful for suppressing various NBIs. The simulation results verify the effectiveness of the algorithm.
    Effect of antenna mutual coupling on channel parameters of the X-type polarization diversity system
    XU Zhi;LIU Qi-zhong;ZHANG Chuan-fang;GUO Jing-li
    J4. 2007, 34(4):  558-561. 
    Abstract ( 2137 )   PDF (861KB) ( 1206 )   Save
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    A useful model for analyzing the effect of mutual coupling (MC) of the X-type polarization diversity system is propounded by the cascading of coupling coefficients matrix from the equivalent network model. The analytical expressions for both the average received power for each antenna element and spatial correlation between elements are also derived, and the effects of both MC and the mean Direction of Arrival (DOA) on the average power and capacity of MIMO wireless channels could be investigated, with the characters of the effect of mutual coupling in a dipole system shown.
    Design of a miniaturized frequency reconfigurable microstrip slot antenna
    WEI Wen-bo;YIN Ying-zeng;GUO Jing-li;LIU Qi-zhong
    J4. 2007, 34(4):  562-565. 
    Abstract ( 2064 )   PDF (979KB) ( 1499 )   Save
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    A novel miniaturized microstrip slot antenna with tunable frequency is proposed. Due to adopting a plane spiral structure, the antenna configuration is more compact, and the size is reduced by approximately 40% compared with a conventional straight slot antenna. By Loading PIN diode switches on the spiral slot, the antenna achieves a good frequency tuning property. Because these switches are directly located on the non-radiation slot, the influence of switches on the frequency tuning property of the antenna is reduced obviously, and the frequency tuning property can be realized more easily.
    Analysis of antennas with the body of revolution radome using the hybrid MoM-PO method
    ZOU Yan-lin;LIU Qi-zhong;GUO Jing-li
    J4. 2007, 34(4):  566-569. 
    Abstract ( 2002 )   PDF (563KB) ( 1136 )   Save
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    This paper presents a hybrid method of moments-physical optics (MoM-PO) method based on the mode decomposition technique for the analysis of the electrically large antenna-body of revolution (BOR) radome system. For the BOR radome, due to its rotation-symmetric property, the mode decomposition technique can be used to reduce the dimension of the problem. For each mode, the equivalent electric and magnetic currents in the flat region of the radome are determined by physical optics (PO), which are then integrated into the method of moments (MoM) equation to eliminate the number of unknowns. This method dramatically reduces the computation complexity and memory demand, and then it can analyze the large scale antenna-BOR radome system efficiently.
    Phase unwrapping approach for extremely large interferograms
    WU Nan;FENG Da-zheng;LIU Bao-quan
    J4. 2007, 34(4):  570-576. 
    Abstract ( 2059 )   PDF (1668KB) ( 1169 )   Save
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    Phase unwrapping is not feasible for extremely large interferograms due to computation time and computer resources. Therefore, we propose a “divide-and-conquer” strategy: divide the whole interferogrm into some patches which are easy to deal with, unwrap each patch independently by using some classical phase unwrapping methods with the good congruence and smaller error propagation, piece all the patches unwrapped together by finding the solution to a minimum weighted continuity cost function and finally interpolate low-coherence areas. Experimental results, carried out on simulated and real data, show that the proposed approach is efficient for unwrapping extremely large interferograms and has not reduced much accuracy with respect to the processing as a whole.
    Performance analysis of the modified 2-D MUSIC algorithm under the effect of the source number estimation Error
    ZHANG Hao;ZHANG Zhi-jun;ZHU Guo-jun
    J4. 2007, 34(4):  577-582. 
    Abstract ( 2284 )   PDF (870KB) ( 1163 )   Save
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    Based on the problem that some unexpected peaks appear in the 2-D MUSIC spectrum when the source number is over estimated and some peaks of the 2-D MUSIC spectrum disappear when the source number is under-estimated. By combining the reducing-dimension technique with the ONE-DIMENSION NOISE SUB-SPACE algorithm, an modified 2-D MUSIC algorithm based on three orthogonal linear arrays is discussed in this paper. It could convert the complicated 2-D processing into three simple 1-D processings. This algorithm utilizes the 1-D DOA which is estimated by the three collateral linear arrays respectively. Computer simulation results indicate that the modified algorithm can give the DOA successfully under the situation of un-known source numbers.
    Characteristics of pulse wave propagation in the random rain medium
    HUANG Ji-ying;LI Ying-le;GONG Shu-hong
    J4. 2007, 34(4):  583-586. 
    Abstract ( 1831 )   PDF (565KB) ( 1148 )   Save
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    Based on the transmission function of an electromagnetic wave in the random rain medium by the random system method, the expressions for the double-frequency correlation function and the intensity of a pulse wave are derived. The pulse fluctuation characteristic and the pulse broadening effect are investigated. The function relation of pulse group velocity with frequency and rain rate is obtained. The effects induced by the EM wave frequency and bandwidth on the pulse broadening velocity is studied and the simulated results are given in the mm band. The results show, based on the calculation in this paper, that the pulse broadening velocity of horizontal polarization wave is greater than that of the vertical polarization wave and that the pulse broadening velocity increases with an increase in bandwidth and rain rate.

    Conformal boundary scheme in FDTD computation of satellite model scattering

    JIANG Yan-nan;GE De-biao;YANG Li-xia
    J4. 2007, 34(4):  587-589. 
    Abstract ( 1789 )   PDF (549KB) ( 1097 )   Save
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    Based on the large dimension of the solar panel compared with the main body in the satellite model, the conformal boundaries are implemented, i.e., the outlines of the total field boundary, near-to-far field extrapolation boundary and absorbing boundary are the same as that of the target. This scheme is applied to the FDTD analysis for satellite model scattering to reduce memory space and computation time. Firstly, the three conformal boundaries in FDTD are considered. The boundary condition at the 270°corner is particularly analyzed in detail. Then the electric dipole radiation is computed to test the applicability of conformal absorbing boundaries, which demonstrates the efficiency in absorbing the outward wave. Finally, the back scattering by the satellite model is computed by using conformal boundaries. The far-zone time domain waveform obtained is in good agreement with that calculated by FDTD of conventional rectangular boundaries, which validates the presented scheme. The FDTD calculation performance is improved using the conformal boundaries in the satellite model. It saves the memory about 40. 7% and shortens the computation time.
    Investigation of characteristics of transmission coefficient from the 1-D band-limited Weierstrass fractal rough surface
    REN Xin-cheng1;2;GUO Li-xin1
    J4. 2007, 34(4):  590-595. 
    Abstract ( 1974 )   PDF (630KB) ( 1073 )   Save
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    The 1-D fractal rough surface is simulated by employing the 1-D normalized band-limited Weierstrass function, the electromagnetic scattering in medium 2 under a rough surface is investigated and the formulae for the transmission coefficients for different polarizations are presented according to the Small Perturbation Method by considering the autocorrelation function and spectrum of the fractal surface. The fractal characteristics, the basic characteristics, the zonal characteristics and the characteristics with the variation with the frequency of the transmission coefficient from the 1-D band-limited Weierstrass fractal rough surface for different polarizations are obtained by numerical calculation. The numerical results show that the influence of the fractal dimension, the rms of rough surface and the incident frequency on the transmission coefficients of the fractal surface is great and obvious, and in case that other conditions are stationary, the fractal dimension, the rms of rough surface and the incident frequency would be greater, and the transmission coefficient would also be greater.
    Fast computation and analysis of multiple antennas mounted on electrically large platforms
    ZHAO Xun-wang;ZHANG Yu;LIANG Chang-hong
    J4. 2007, 34(4):  596-599. 
    Abstract ( 1984 )   PDF (840KB) ( 1319 )   Save
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    In order to analyze the radiation behavior of multiple wire antennas mounted on electrically large platforms under limited computer resources, the multilevel fast multipole algorithm (MLFMA) with an adaptive number of levels is implemented. BiCGStab(l) is used as the solver, which combines GMRES(l) and Bi-CG and profits from both. Based on the “physical neighbor”, a novel near-field preconditioner is proposed which improves greatly the convergence of BiCGStab(l). The radiation patterns in the far field of multiple ultra-shortwave antennas mounted on a ship model with the comparative size to real ones are calculated. Numerical results show that the technique is exact and efficient.
    Study on the creeping ray-tracing algorithm of NURBS-UTD
    WANG Nan;LIANG Chang-hong;ZHANG Yu;CHEN Ming
    J4. 2007, 34(4):  600-604. 
    Abstract ( 1705 )   PDF (1028KB) ( 891 )   Save
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    To overcome the drawback that the method of the uniform geometrical theory of diffraction can not be applied to arbitrary curved targets, the method of the uniform geometrical theory of diffraction based on models constructed by arbitrary curved surfaces is studied and the algorithm that traces the creeping rays which are in the highest flight in the shadow region is presented where the numerical differential geometry method is introduced in the process of ray-tracing. What is studied here makes the method of the uniform geometrical theory of diffraction able to be applied to analyze complex electromagnetic targets which can not be dealt with before. The algorithm can be applied to models constructed by arbitrary curved surfaces including the board, cylinder and cone that are already used and the validity and usefulness can be seen from numerical results.
    Automatic human gait recognition using temporal templates
    CHEN Shi1;TIAN Yu-min1;HUANG Wan-hong2;GAO You-xing1
    J4. 2007, 34(4):  605-610. 
    Abstract ( 2032 )   PDF (835KB) ( 1328 )   Save
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    A novel temporal templates representation method for gait analysis and recognition applications is introduced. The method includes following steps: first, silhouette extraction is performed to the images of the video sequence; secondly, the gait cycle including two steps is detected by analysizing the contour points distribution of silhouette sequence; thirdly, by cumulating interframes forwards sihouette differences, two single step history images (SSHI) are obtained to represent how and where human walking is evolved. The SSHI image is then segmented by a family of rectangles, from which a set of local moment invariant vectors are abstracted to be the feature vectors of the SSHIs. These feature vectors are finally used to achieve gait recognition. Recognition capability is illustrated by an 85. 57% CCR on Soton database and the results show that the method outperforms the existing methods.

    Application of joint Contourlet and Bandelet transforms in image compression

    SUN Wen-fang;SONG Bei-bei;ZHAO Yi-gong
    J4. 2007, 34(4):  611-615. 
    Abstract ( 2127 )   PDF (554KB) ( 1226 )   Save
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    The wavelet transform suffers from the limitation of poor directional selectivity. To overcome this disadvantage, a novel scheme with joint Contourlet and Bandelet transform is proposed. First the image is decomposed into different frequency subbands by the wavelet transform, and then the high frequency subband is further decomposed into directional subbands by directional filterbank. Next, the Bandelet transform is taken on each directional subband. The proposed multidirectional and multiscale transform with critical sampling can represent the geometrical features such as edges and texture more sparsely, which is of great benefit to image compression. Finally, the bit plane and contextual coding procedure of the JPEG2000 scheme are applied to quantized transform coefficients to realize image compression. Experiments show that the proposed algorithms evidently outperform JPEG2000 for the images with abundant edges and texture.

    Orthogonal immune clone particle swarm optimization for the SAT problem
    CONG Lin;SHA Yu-heng;JIAO Li-cheng
    J4. 2007, 34(4):  616-621. 
    Abstract ( 2253 )   Save
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    Based on the Binary Particle Swarm Optimization given by Kennedy and Eberhart and the clonal selection theory, a novel Orthogonal Immune Clone Particle Swarm Optimization (OICPSO) was presented to solve SAT problems. In this paper, the SAT problems are converted into global minimum optimization problems. In order to increase the convergence speed, according to the known knowledge of clauses, the individual’s assign probability is calculated for being used to initialize the population. To avoid the algorithm prematurity and enhance the uniformity of individual’s distribution, the discrete orthogonal crossover operator is used in immune gene operations, and the immune PSO evolutionary operators to the SAT problems are presented. In experiments, 3700 benchmark SAT problems in SATLIB are used to test the performance of OICPSO. The number of variables of these problems ranges from 20 to 250. Moreover, the performance of OICPSO is compared with the standard Particle Swarm Optimization (SPSO) and Immune Clonal Selection Algorithm (ICSA). All experimental results show that the success ratio of OICPSO is the highest and that the run time and number of function evaluations are the least among the three algorithms.
    Buffer and wiresizing optimization based on MOGA/SOS
    QI Chang;WANG Gao-feng
    J4. 2007, 34(4):  622-628. 
    Abstract ( 2047 )   PDF (883KB) ( 966 )   Save
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    We present a new multi-objective genetic algorithm(MOGA) which uses a single objective sorting(SOS) method for constructing the non-dominated set to solve the multi-objective interconnect buffer and wiresizing optimization problem under a distributed RLC model. The optimal objective includes the interconnect delay, signal waveform and routing area. We use a new method to calculate the lower bound of crosstalk, and use it as a constraint. The MOGA/SOS optimal algorithm provides a smooth trade-off among signal delay, wave form, and routing area. Extensive experimental results show that our algorithm is scalable with the problem size. Furthermore, compared to the solution based on an Elmore delay model, our solution reduces the total routing area by up to 30%, and the delay to the critical sinks by up to 25%. At the same time it improves crosstalk up to 25. 73% on average.
    Public-key watermarking algorithm resistant to geometric attacks
    LIU Xiang-li1;KOU Wei-dong1;WANG Zhi-guo2
    J4. 2007, 34(4):  629-633. 
    Abstract ( 1655 )   PDF (713KB) ( 909 )   Save
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    Aiming at two important issues in the watermark system,public watermark detection and geometric attack, a public-key watermark algorithm is proposed, which is resistant to geometric attacks. The embedment and extraction of watermark are based on the normalized image. The normalized image is unique under a certain size when the image is under affine geometric attacks. The private key is used to generate embedding watermarks. The public key is generated by the private key through phase-shift, and used in watermark detection. Through the correlation estimation, the watermark is extracted bit by bit. The results from Stirmark software show that this algorithm is robust to a wide range of geometric attacks. With the use of the public key to the watermark extraction, the public verification of a watermark can be achieved.
    New signature scheme based on the strong RSA assumption
    LI Yong-jiang1;2;LI Wei3;ZHU Xiao-yan1;GE Jian-hua1
    J4. 2007, 34(4):  634-637. 
    Abstract ( 2002 )   PDF (499KB) ( 1250 )   Save
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    To promote the speed of the random signature generation and verification algorithms under the strong RSA hardness assumption, a new signature scheme is proposed. In this scheme, by randomly selecting the exponent e under modular n and using the RSA algorithm to sign the message bound with e, the redundant parameters in Cao et al.’s signature scheme are simplified or deleted. The new scheme is proved to be secure in the Random Oracle Model. Detailed comparisons show that the speed of the new scheme is at least two times faster than that of the other schemes of such a kind.
    Proxy signature scheme with fast revocation
    YU Yong1;YANG Bo1;2;SUN Ying2;ZHU Sheng-lin2
    J4. 2007, 34(4):  638-641. 
    Abstract ( 1645 )   PDF (488KB) ( 871 )   Save
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    Many proxy signature schemes have the defect that they cannot solve the proxy revocation problem. Based on the bilinear pairings, a new proxy signature scheme is proposed in this paper. Motivated by the idea of(2, 2) threshold, a security mediator (SEM) is introduced in our scheme to (1) help a proxy signer to generate valid proxy signatures, (2) examine whether a proxy signer signs according to the warrant, and (3) check the revocation of a proxy signer. It is shown that the proposed scheme satisfies all the security requirements for a secure proxy signature. Moreover, a proxy signer must cooperate with the SEM to generate a valid proxy signature, which makes the new scheme have an effective and fast proxy revocation.
    On the autocorrelation function of a new class of sextic residue sequences
    DU Xiao-ni1;2;CHEN Zhi-xiong1;3;CHEN Ru-wei1;XIAO Guo-zhen1
    J4. 2007, 34(4):  642-646. 
    Abstract ( 1900 )   PDF (474KB) ( 864 )   Save
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    On the autocorrelation function of a new class of sextic residue sequences
    DU Xiao-ni1;2;CHEN Zhi-xiong1;3;CHEN Ru-wei1;XIAO Guo-zhen1
    J4. 2007, 34(4):  642-646. 
    Abstract ( 1836 )   PDF (474KB) ( 941 )   Save
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    Based on the theory of cyclotomy, a new class of binary sextic residue sequences with the period p of the form 6f+1 with f odd and p prime is constructed by selecting the union of the first three classes within the six cyclotomic classes of order six as the characteristic set. The new sequences are proved in theory to be balanced with a five-valued autocorrelation, and their out of phase autocorrelation depends solely on the square sum decomposition of p. Given a period large enough, the out of phase autocorrelation approaches zero and the sequences approximately have the ideal autocorrealtion. Also it is pointed that the out of phase autocorrelation of the sequences with certain values of period p are four-valued, that all of them approximate 1/p, and that their pattern distributions are balanced.
    Adaptive threshold technique for motion detection based on the two-dimensional spatio-temporal entropic principle
    LIU Yang;LI Yu-shan
    J4. 2007, 34(4):  647-653. 
    Abstract ( 1611 )   PDF (1328KB) ( 975 )   Save
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    In order to determine the detection threshold in moving objects extraction, an adaptive detection threshold determination method based on the two-dimensional spatio-temporal entropic principle is proposed. The motion detection is reduced to two binary partition problems, and two-dimensional entropic principle is used to determine the threshold vector(S,T), where the explicit function form and parameters of background distribution are not needed to be known. A fast algorithm for calculating the two-dimensional entropic threshold is put forward, in which repeated calculation is avoided by using the integral and iterative operation, thus reducing the computational complexity from O(N4) to O(N2) for an N gray levels image. The experimental results show that the information of moving objects which have a low contrast to background can also be extracted completely by this method in real time.
    Noisy image zooming algorithm based on the wavelet and scalar-valued diffusion equation
    HAO Bin-bin;FENG Xiang-chu
    J4. 2007, 34(4):  654-658. 
    Abstract ( 1943 )   PDF (1074KB) ( 1225 )   Save
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    Combining wavelet multi-resolution analysis and the discrete iteration of scalar valued diffusion, a new noisy image zooming model is proposed that presents the original image as the low pass filter of wavelet analysis, and we estimate its high pass filter and use the discrete one iteration of the forward and backward (FAB) diffusion equation to the zoomed image. Because of the threshold of the wavelet coefficients and the property that FAB diffusivity acts as local forward diffusion in the small gradient region, the image is denoised as well as enlarged, and as local backward diffusion in the large gradient region the zoomed image is edge preserved. Some numerical experiments illustrate that not only does the proposed method zooms images, but also the processed images look much clearer and smoother.
    Fast group key agreement protocols in Ad Hoc networks
    ZHONG Huan1;2;XU Chun-xiang3;MA Hua4
    J4. 2007, 34(4):  659-663. 
    Abstract ( 1812 )   PDF (560KB) ( 1184 )   Save
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    Based on the security of the discrete logarithm, an FGKA (fast group key agreement) protocol, that fits for small Ad Hoc networks, is presented. It combines contribution information of all members with the secret value selected by the sponsor. To fits for the large Ad Hoc network, the above protocol is extended to the AT-FGKA(Arbitrary Topology-FGKA) protocol which can be adapted to an arbitrary network by using the k-ary tree. Finally, dynamic member maintenance protocols as well as security analysis and efficiency comparison are described, which shows that the former has little communication and computation, and that the latter can reduce communication cost effectively.
    Performance comparison and analysis of the tree-based on-demand multicast routing protocol in Ad Hoc networks
    XU Rui;LI Wei-hua;CHEN Hua-sheng
    J4. 2007, 34(4):  664-668. 
    Abstract ( 2315 )   PDF (785KB) ( 1197 )   Save
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    This paper presents a research on two tree-based on-demand multicast routing protocols, namely ADMR and MAODV. It analyzes the influences of different tree structures and different tree maintenances on the performance of these two protocols and draws a conclusion. A comparative performance evaluation of these protocols under different MANET scenarios is given by the ns2 platform. Simulation results further verifies the analytic results. The following conclusions can be drawn from the simulation results that the shared tree structure and the routing overheads of tree maintenance form the bottleneck of MAODV and that ADMR has a higher PDR and a shorter delay.
    Total variation energy functional with restrictions on the finite ridgelet domain
    LU Cheng-wu1;2;SONG Yi-mei1;SONG Guo-xiang1
    J4. 2007, 34(4):  669-672. 
    Abstract ( 2192 )   PDF (691KB) ( 1339 )   Save
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    To reduce the “wrap around” aliased lines from finite ridgelets transform (FRIT), the aliased lines are regarded as a kind of oscillation. Firstly, the nonlinear thresholding strategy is applied to coefficients of FRIT. And then, the total variational regularization method is introduced to suppress the oscillation. So a minimization total variation energy functional model with restrictions on the FRIT domain is established. By assuming that the coefficients remaining are identical with those of the restoration image,the feasible domain of the model is determined. Finally, the projected gradient algorithm is used to solve the model. Experiments show that the approach is very robust to noise, and that the aliased line are suppressed efficiently, and at the same time, remove noise and maintain the edge.
    Modelling concurrent workflow with the extended interval temporal logic
    LEI Li-hui;DUAN Zhen-hua
    J4. 2007, 34(4):  673-680. 
    Abstract ( 1982 )   PDF (673KB) ( 1356 )   Save
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    According to the concurrent workflow patterns, split and anyorder, and their implementation in the systems adopting the central architecture, the interval temporal logic is extended by two new operators: shuffle and restricted shuffle. The formulas connected with the new operators are suitable for representing concurrent workflows, which is proved with the partial-order relationship among the states maintained by the workflow and the length relationship among the intervals that satisfy those formulas describing the workflow and the participating activities. An example is given to illustrate how to use the extended interval temporal logic to represent the activities and the concurrent workflow composed of these activities. The interval temporal logic model for concurrent workflows can be obtained by this method. This model can be employed to verify the liveness and safety of concurrent workflows by utilizing some tools and theories based on interval temporal logic, which guarantees the reliability of the design of concurrent workflows.