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    20 December 2011 Volume 38 Issue 6
      
    Original Articles
    Secure routing protocol based on probability in sensor networks
    TANG Di;YANG Xiaoniu;LI Jiandong
    J4. 2011, 38(6):  1-7.  doi:10.3969/j.issn.1001-2400.2011.06.001
    Abstract ( 1874 )   PDF (629KB) ( 1168 )   Save
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    In wireless sensor networks, the traditional intrusion detection can not detect the compromised nodes immediately. In this paper, we propose a secure routing protocol (Secure Relay Grid Routing Protocol) based on probability prediction to solve this problem. In the protocol, the network is divided into different small grids. Utilizing the geographic information and intrusion detection information, the proposed protocol is designed with a routing metric which is based on a mathematical prediction model. The routing metric could guarantee that the message detours those compromised grids that have not been detected by the intrusion detection. Theoretical analysis and OPNET simulation results show that the proposed protocol can provide a high delivery ratio and decrease the number of the compromised packets.

    Fat tree of Mesh(FoM): a new optical network on chip architecture
    WANG Shiqing;GU Huaxi;ZHU Zhangming
    J4. 2011, 38(6):  8-14+29.  doi:10.3969/j.issn.1001-2400.2011.06.002
    Abstract ( 1153 )   PDF (904KB) ( 1152 )   Save
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    Based on silicon photonic technology, optical network-on-chip (ONoC) can offer significant bandwidth and power advantages, which provides a promising solution to overcoming the limitations of traditional electronic interconnect. In this paper, based on the advantages of Mesh and Fat Tree, we propose a new ONoC including its topology, scaling and routing algorithm and so on. We have simulated and compared several ONoCs based on the topologies including Mesh, Fat Tree (FT) and Butterfly Fat Tree (BFT) in terms of the end-to-end delay, network throughput and power consumption. The results show that the new ONoC has advantages in terms of network performance and cost.

    Multistage minimal module method for space-time interference suppression GPS receivers
    HUANG Qingdong;ZHANG Linrang;WANG Chun;ZHANG Bo
    J4. 2011, 38(6):  15-21+88.  doi:10.3969/j.issn.1001-2400.2011.06.003
    Abstract ( 1507 )   PDF (1129KB) ( 1002 )   Save
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    For suppression of the influence of impulsive noise spikes (outliers) from desired signal direction of arrival in GPS signals, the multistage minimal module cascaded canceller is proposed. The method substitutes the weights of the multistage Winner filter for the minimal module weights, which have the minimal module of the samples quotient, and is adopted in space-time anti-jamming processing in the GPS receiver. The method has the prominent ability to restrict the influence of impulsive noise spikes (outliers) from desired signal direction of arrival to adaptive weights, and the ability of low complexity, as well as fast convergence. Simulation results indicate the method achieves a better fast convergence ability and good performance in reducing the influence of impulsive noise spikes (outliers) on adaptive weights.

    New frame segmentation method for radar HRRPs
    WANG Penghui;DU Lan;LIU Hongwei;LI Yanbing;WU Zhaoping
    J4. 2011, 38(6):  22-29.  doi:10.3969/j.issn.1001-2400.2011.06.004
    Abstract ( 1928 )   PDF (1589KB) ( 956 )   Save
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    To deal with the target-aspect sensitivity of radar High Resolution Range Profiles (HRRP), a novel frame segmentation method is proposed. Firstly, the statistical characteristic of HRRPs' frequency spectrum amplitudes is analyzed and assumed to be joint Gaussian distribution. Then Probabilistic Principle Component Analysis (PPCA) is employed to model each sub-frame and the Expectation Maximization (EM) algorithm is adopted to estimate the model parameters. Finally, the adjacent sub-frames which have the minimum Kullback-Leibler (KL) distance are merged iteratively to finish the frame segmentation. Both segmentation results and recognition performance of measured data verify the effectiveness of this method.

    Robust registration of multimodality medical images based on the principal ordinal feature and hybrid entropy
    LI Qi;JI Hongbing;TONG Ming
    J4. 2011, 38(6):  30-36+145.  doi:10.3969/j.issn.1001-2400.2011.06.005
    Abstract ( 1304 )   PDF (4434KB) ( 1115 )   Save
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    To improve the robustness and precision of multimodality medical image registration, a principal ordinal feature and hybrid entropy based registration method is presented. A principal ordinal feature is defined and used to represent the spatial information between the neighboring pixels and the properties of the specified micro-structure in medical images. Integrating with pixel intensities, a similarity measure based on hybrid entropy is defined to register multimodality images. The proposed method is demonstrated using several pairs of multimodality medical images and experimental results show that the noise of images can be effectively suppressed and that compared with some existing methods, the proposed registration algorithm is of higher precision and better robustness.

    New quality evaluation technique for the SiC epilayer
    MA Gelin;ZHANG Yuming;ZHANG Yimen;MA Zhongfa
    J4. 2011, 38(6):  37-43+96.  doi:10.3969/j.issn.1001-2400.2011.06.006
    Abstract ( 1193 )   PDF (1190KB) ( 940 )   Save
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    Considering that many characterization techniques used to evaluate the quality properties of the Silicon Carbide (SiC) epilayer result in high cost, long time, easy damage and being unable to carry out on-line test, the Infrared Specular Reflection (IRSR) Spectroscopy, Raman Scattering (RS) Spectroscopy, X-Ray Diffraction (XRD), Atom Force Microscopy(AFM) and X-ray Photoelectron energy Spectroscopy (XPS) are used to study the quality test of the 4H-SiC wafer. Results show that the IRSR spectrum can provide not only the quality parameters offered by RS, XRD, AFM and XPS but also agree with the comprehensive results from them. It is demonstrated that ISRS can be used as a low cost, rapid, non-destructive and on-line monitoring technique for the quality control of the SiC epilayer.

    Efficient infrared image background prediction in CUDA
    WU Xin;ZHANG Jianqi;LIU Delian;HUANG Xi;HE Guojing
    J4. 2011, 38(6):  44-51.  doi:10.3969/j.issn.1001-2400.2011.06.007
    Abstract ( 1640 )   PDF (1021KB) ( 991 )   Save
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    Background prediction in infrared is a classical method for small and dim target detection. Taking account of the convolution's time-consuming property, an efficient method for infrared image background prediction based on CUDA (Compute Unified Device Architecture) is proposed. By considering the feature of CUDA and analyzing the process of background prediction, it is re-realized. Using the framework of CUDA and taking advantage of the powerful parallel computing ability of GPU (Graphic Processing Unit), background prediction from infrared images is rapidly and efficiently completed. For further raising the efficiency of the method, the inseparable convolution matrix used by background prediction is broken up into several separable matrices, where a general method for separating the convolution matrix is presented. Applying this method to actual infrared image's background prediction, the computation efficiency is raised more than 130 times compared with the traditional method based on CPU.

    Design of wide band-ratio coupled line wilkinson power divider for dual-band operation
    YANG Yanjiong;LI Aiqin;LI Xi;YANG Lin;GONG Shuxi
    J4. 2011, 38(6):  52-54.  doi:10.3969/j.issn.1001-2400.2011.06.008
    Abstract ( 1272 )   PDF (1136KB) ( 1158 )   Save
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    Design of a coupled line with a pair of isolation stubs is presented. Dual-band operation in the Wilkinson power divider can be achieved and also, the overall structure of the power divider can be simplified. Compared with the power divider directly connected by an isolation resistor, the one consisting of isolation stubs reduces the parasitic effects between transmission lines. A 1.0GHz, 2.5GHz dual-band Wilkinson power divider is designed and processed. It is proved that simulation results agree with the experimental ones and the power divider works well.

    Instantaneous frequency measurement method for the broadband non-stationary signal
    WANG Hai;FAN Wenjing;ZHANG Shengfeng
    J4. 2011, 38(6):  55-61.  doi:10.3969/j.issn.1001-2400.2011.06.009
    Abstract ( 1378 )   PDF (1057KB) ( 1013 )   Save
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    An instantaneous frequency measurement method for broadband non-stationary signal is presented. The signal can be decomposed into progressive single-frequency signals by added qualification adaptive filters. According to their phase functions of analytical signals, the instantaneous frequencies are obtained. By integration of time-frequency relationship of all components, the instantaneous frequencies of broadband non-stationary signal are accurately measured. Simulation and error analysis prove that this method overcomes the difficulties in instantaneous frequency measuring of Fourier analysis, Wavelet transformation and Hilbert-Huang algorithm for the broadband non-stationary signal. In the whole analyzed frequency band it can achieve a higher frequency measurement resolution and has a measurement error of less than 0.2MHz for the signals with an SNR of above 0dB . For 8μs long signal, this method has a better real-time processing capability, but an initial  operational delay of 25.816μs. Therefore, this method can meet the requirements of instantaneous frequency measurement for the broadband non-stationary signal.

    Effective connectivity of the Chinese character visual-processing network: a resting state research
    ZHAO Jizheng;ZHAO Heng;LI Jun
    J4. 2011, 38(6):  62-67.  doi:10.3969/j.issn.1001-2400.2011.06.010
    Abstract ( 1515 )   PDF (1686KB) ( 1115 )   Save
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    Neuroimaging studies have revealed that several brain regions play an important role in the visual processing of Chinese characters, including the left parts of inferior occipital gyrus, middle fusiform gyrus, superior parietal lobule, and middle frontal gyrus. In order to investigate the intercommunicating pattern among these brain regions in the resting state, the method of the multivariate Granger Causality Model (GCM) is employed to analyze the time series of these brain regions, which could provide robustness to false causality in case of variables with a common source. The results demonstrate that there are significantly bidirectional Granger causality connections between the left inferior occipital gyrus and superior parietal lobule, as well as between the left middle fusiform gyrus and superior parietal lobule; the left inferior occipital gyrus Granger-causes the left middle frontal gyrus; the left middle fusiform gyrus is Granger-caused by the left middle frontal gyrus. All the results above reveal the intercommunications among the brain regions which respond to the visual processing of Chinese characters without any explicit tasks, and indicate a preparatory brain networks for the highly probable character input in the resting state.

    Novel image restoration method with structure tensor fitting
    WANG Xudong;FENG Xiangchu;BAI Jian
    J4. 2011, 38(6):  68-74.  doi:10.3969/j.issn.1001-2400.2011.06.011
    Abstract ( 1648 )   PDF (10750KB) ( 1164 )   Save
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    A novel model of image restoration is proposed. The structure tensor field is calculated after smoothing the noised image by anisotropic diffusion. Then the image is reconstructed by fitting the structure tensor field and the noise image. The proposed method overcomes shortcomings of the classical anisotropic diffusion method. Numerical experiments verify that the proposed method remove noise effectively while preserving structures well.

    Study of monostatic and bistatic polarimetric scattering from the  two-dimensional Gauss rough surface characterized by textures
    LIU Wei;GUO Lixin;WANG Anqi
    J4. 2011, 38(6):  75-81+102.  doi:10.3969/j.issn.1001-2400.2011.06.012
    Abstract ( 1227 )   PDF (1856KB) ( 960 )   Save
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    A two-dimensional Gauss rough surface characterized by textures is presented and the properties of polarimetric scattering from the surface are studied. The rough surface characterized by textures can be obtained through the angle rotating in Fourier transform with the ratio of the two correlation lengths large enough. The scattered field is derived in the Cartesian coordinate system through the integration of scattering facets with the elliptic polarized incidence wave. The polarized radar cross section (RCS) from the Gaussian rough surface characterized by textures is computed. Several numerical results exhibit the influence of incident angle, texture angle, correlation length and root mean square height on the polarimetric scattering from the texture rough surface.

    Target localization method for the bistatic MIMO radar in the presence of mutual coupling of receiver and transmitter arrays
    GUO Yiduo;ZHANG Yongshun;ZHANG Linrang;TONG Ningning
    J4. 2011, 38(6):  82-88.  doi:10.3969/j.issn.1001-2400.2011.06.013
    Abstract ( 1361 )   PDF (578KB) ( 928 )   Save
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    By using the banded symmetric and Toeplitz matrix model for the mutual coupling of uniformly linear array(ULA), a subspace-based target localization and mutual coupling self-calibration method is proposed for the bistatic MIMO radar. The new algorithm can “decouple” the 2-dimensional (2-D) angles and mutual coupling parameters, and provide a similar estimated performance to 2-D MUSIC without the knowledge of the sensor mutual coupling matrix. At the same time, an accurate estimate of mutual coupling matrix based on the estimated 2-D angles can also be achieved simultaneously for self-calibration of the bistatic MIMO radar. The 2-D angles estimation and mutual coupling estimation can be completed just using one-dimensional search or polynomial rooting, with no high-dimensional nonlinear search and convergence burden involved, so the computatinal cost is low. The correction and efficiency of the proposed method are verified by computer simulation results.

    New method for TDOA sorting and pairing using TDOAs' correlation
    REN Wenjuan;HU Donghui;DING Chibiao
    J4. 2011, 38(6):  89-96.  doi:10.3969/j.issn.1001-2400.2011.06.014
    Abstract ( 1291 )   PDF (573KB) ( 1019 )   Save
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    For eliminating location ambiguity of three familiar types of high PRF (pulse repetition frequency) signal in the TDOA (time difference of arrival) passive location system, a new method for TDOA sorting and pairing is put forward. The new method defines the correlation coefficient which describes the correlation between a pair of TDOAs. Firstly, two TDOA sequences of a certain target are sorted by calculating the correlation coefficient, so TDOA sequences' sorting and pairing is accomplished simultaneously, and then the correlation coefficient matrix of single target's pairing TDOA sequences is analyzed, and false pairs of TDOAs are eliminated according to the pairing representation of the high PRF signal. Simulation results show that the new method is able to reduce the number of false pairs of TDOAs, so it can reduce false locations and improve location ambiguity effectively.

    Phase unwrapping algorithm with CRT for multi-band InSAR
    JIN Guowang;ZHANG Hongmin;XU Qing;GONG Zhihui
    J4. 2011, 38(6):  97-102.  doi:10.3969/j.issn.1001-2400.2011.06.015
    Abstract ( 1447 )   PDF (6640KB) ( 934 )   Save
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    For the InSAR System, when the wavelength is longer, the frequency of fringes will be lower, the phase unwrapping will be easier, and the accuracy of derived heights will be lower. However, when the wavelength is shorter, the frequency of fringes will be higher, the phase unwrapping will be more difficult, and the accuracy of derived heights will be higher. In order to make the best use of compensatory information in multi-band InSAR phases, the phase unwrapping algorithm with the Chinese Remainder Theorem for multi-band InSAR is designed. The multi-band interferograms simulated from DEM are applied to do phase unwrapping experiments. The satisfying phase unwrapping results are obtained. The difficulty in phase unwrapping of sub-sampling interferometric phases due to great hypsography or longer baseline is removed.

    Algorithm for the adaptive Kalman filter in AHRS
    TIAN Yi;SUN Jinhai;LI Jinhai;YAN Yuepeng
    J4. 2011, 38(6):  103-107+122.  doi:10.3969/j.issn.1001-2400.2011.06.016
    Abstract ( 1411 )   PDF (601KB) ( 1321 )   Save
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    Due to the uncertainty of measurement noise, the accuracy of the Kalman filter is affected seriously while measuring the vehicle attitude in the Attitude and Heading Reference System(AHRS). The sudden change of measurement noise brought by interference of the system even leads to filter divergence. An algorithm for the adaptive Kalman Filter used in AHRS is presented in this paper, which is able to estimate the measurement noise in real time according to observation data and improve the accuracy of the Kalman Filter. Simulation result shows that the results of the Kalman filter diverge clearly even though the measurement noise varies, and that the adaptive Kalman filter results converge very well. The system stability is markedly improved without significant increase in computing complexity.

    Robust adaptive beamforming algorithm based on the eigenvector constraint for short-range clutter suppression
    LIU Tao;LU Changjie;LIAO Hui;MA Hongguang
    J4. 2011, 38(6):  108-112+129.  doi:10.3969/j.issn.1001-2400.2011.06.017
    Abstract ( 1167 )   PDF (1432KB) ( 891 )   Save
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    For the cancellation of the severe range dependent short-range clutter in the case of range ambiguity of non-side-looking arrays (NSL), an elevation filtering algorithm is proposed. Based on the eigendecomposition of the covariance matrix, an eigenvector selecting method is developed. Using this method, eigenvectors corresponding to short-range and long-range are selected as constraints for the adaptive beamformer. It is shown that the eigenvector constrained (EVC) beamforming algorithm demonstrates the advantages of low sensitivity to steering angle error or steering vector mismatch and great robust main-lobe protecting ability over conventional algorithms. Computer simulation results are presented that illustrate the effectiveness of the proposed algorithm.

    Small sample signals' decorrelation using the coherent accumulation vector' spatial smoothing
    LI Tao;LI Guolin;XU Heng;LIAO Huirong
    J4. 2011, 38(6):  113-116+139.  doi:10.3969/j.issn.1001-2400.2011.06.018
    Abstract ( 1092 )   PDF (1271KB) ( 886 )   Save
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    When estimating the DOA of narrowband signals, if the snapshot number is small, decorrelation operation is necessary because for all the snapshots, their amplitude and phase are unchanged, which makes signals from different directions coherent. For this kind of signals, existing decorrelation algorithms always need too much computation or are sensitive to SNR. This paper proposes taking coherent accumulation operation for array outputs, and the resulting vector is used to construct a matrix by forward and backward smoothing. By taking SVD of this matrix, the signal and noise subspace is obtained then. Simulation results indicate that this method is of excellent noise-resistance performance with great computational complexity reduction in contract to existing decorrelation algorithms. It has the same performance as ESVD algorithms based on eigen-decomposition, when the SNR is higher than -14dB.

    Study of processing and display technologies for 3D digital earth
    YANG Hailin;WANG Jiaxin
    J4. 2011, 38(6):  117-122.  doi:10.3969/j.issn.1001-2400.2011.06.019
    Abstract ( 1015 )   PDF (5170KB) ( 999 )   Save
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    The layered approach of linear object, such as the boundary lines for digital earth is proposed. Before linear object is divided into LOD, the intersection points of linear object and block adjacent grid at all levels need to be calculated, ether the intersection points of linear object line segment and triangle. Then how to measure terrain of Earth's surface and show is described. By calculating the rotation axis, rotation matrix and the terrain height, the calculated measure line is closed to all levels terrain triangles. Finally, the display method of red and blue stereographic images is detailed. View point focus on the left and right eye location, and GPU outputs to two texture map. GPU shader processes and outputs red and blue stereo image. The flight simulation system on digital earth, which is developed based on these technologies, provides strong support for flight training.

    Mismatch analysis and high-level modeling of passive components  in successive approximation A/D converters
    TONG Xingyuan;YANG Yintang;ZHU Zhangming;LIU Lianxi
    J4. 2011, 38(6):  123-129.  doi:10.3969/j.issn.1001-2400.2011.06.020
    Abstract ( 1145 )   PDF (1331KB) ( 1082 )   Save
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    The paper focuses on the research on the mismatch of the passive components in the SAR (Successive Approximation Register) ADC (Analog-to-Digital Converter). Based on the charge redistribution, voltage division and hybrid SAR ADC architectures, the matching requirements of their internal passive component networks are explored with theoretical derivation and verified by high-level modeling using Matlab. Furthermore, without adding any matching requirement of the internal passive components, a novel charge redistribution approach based on the unit scalable capacitor is proposed. With the unit capacitor replacing the non-integral scalable capacitor and by adding several additional logic control signals, this new approach is easier to realize in process than the traditional approach and is very suitable for embedded SoC applications.

    Provably secure threshold FFS signature scheme in  the random oracle model
    XIAO Hong;WANG Hong;MA Runnian;CUI Jie
    J4. 2011, 38(6):  130-133+151.  doi:10.3969/j.issn.1001-2400.2011.06.021
    Abstract ( 1395 )   PDF (407KB) ( 860 )   Save
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    A rigorous security proof of a provably adaptively-secure optimal-resilience threshold Feige-Fiat-Shamir signature scheme based on strong RSA assumption is given. In the case of the random oracle model, if the basic Feige-Fiat-Shamir signature scheme is unforgeable against the adaptive chosen message attack, and computing the discrete logarithm modulo a safe prime is hard, the new scheme can be proved to be unforgeable, robust and secure against adaptive adversary.

    Quasi orthogonal group SFTBC transmit scheme with linear constellation precoding
    ZHAN Jinlong;LU Jianjun;LU Guangyue
    J4. 2011, 38(6):  134-139.  doi:10.3969/j.issn.1001-2400.2011.06.022
    Abstract ( 1844 )   PDF (601KB) ( 5912 )   Save
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    Based on LCP(Linear Constellation Precoding), a novel multi-antenna transmit scheme is proposed to make the quasi orthogonal group SFTBC obtain full frequency diversity. In the scheme, LCP and quasi orthogonal group SFTBC are cascaded, thus making SFTBC based on quasi-orthogonal design obtain full frequency diversity and space diversity. Both theoretical analysis of pair-wise error probability and BER simulation results are given. Simulation results show that the proposed scheme has a performance gain of at least 1dB compared to traditional ones.

    Research on the test and verification system of the ARINC 659 fault-tolerant backplane data bus
    ZHANG Ximin;WEI Ting
    J4. 2011, 38(6):  140-145.  doi:10.3969/j.issn.1001-2400.2011.06.023
    Abstract ( 1283 )   PDF (2915KB) ( 1096 )   Save
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    The ARINC 659 data bus is a high reliability and high-integrity avionic standard backplane bus designed to provide fault tolerance and robustness partition in time and memory space. It is a key component of the integrated modular avionics system. The ARINC 659 data bus is the property key technique of the Honeywell Company, and it places a stick embargo on the correlative productions for other companies especially for our country. In this paper, the independent innovative ARINC 659 data bus interface ASIC, which has a special microprocessor, and its Frame Description Language compiler are developed. The design and realization of the communication test platform are presented, which consists of the three complements: the ARINC 659 data bus interface card, the communication node controller and the communication test-bed of the data bus. The debug and test configurations of the hardware and software are explored. The methods are given to test and verify the function under the test environment according to the ARINC 659 Specification, and the result shows the correctness and integrity of the design. The research has been applied in the avionic safe critical systems, and the systems benefit from it with higher reliability and lower LLC.

    Non-rigid object tracking based on the boundary fragment  feature and level set segmentation
    GAO Jing;BI Duyan;ZHAO Xiaolin
    J4. 2011, 38(6):  146-151.  doi:10.3969/j.issn.1001-2400.2011.06.024
    Abstract ( 1319 )   PDF (5583KB) ( 930 )   Save
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    To track non-rigid objects exactly, conventional methods typically suffer from two problems: 1) fast local shape deformation and 2) occlusion. This paper proposes a novel non-rigid object tracking algorithm based on boundary fragments matching and level set segmentation. Our approach embeds the discriminative object boundary feature learned by Adaboost into the levelset energy function. Both efficiency and adaptability of our algorithm are demonstrated by experimental results.

    SAR image thresholding segmentation based on the bacteria foraging algorithm
    MA Miao;LIANG Jianhui;GUO Min
    J4. 2011, 38(6):  152-158+178.  doi:10.3969/j.issn.1001-2400.2011.06.025
    Abstract ( 1432 )   PDF (2110KB) ( 1024 )   Save
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    In order to increase the speed and the accuracy of Synthetic Aperture Radar(SAR) image segmentation, a new thresholding segmentation method is proposed, which integrates the Bacterial Foraging Algorithm (BFA) and two-dimensional grey entropy. After the basic BFA is analyzed deeply, the method improves the search speed of the best threshold via shrinking the foraging space of the bacterial swarm. And then, an improved two-dimensional grey entropy model is regarded as the fitness function of our optimized BFA. Finally, the best threshold is located gradually and quickly by three behaviors of the bacterial swarm, i.e., chemotaxis, and reproduction, elimination and dispersal. Experimental results show that the proposed method is superior to some segmentation methods based on the Genetic Algorithm (GA) and Artificial Fish Swarm Algorithm (AFSA) in convergence, stability and segmentation effects.

    Fast recognition method for generator polynomial of BCH codes
    Lü Xizai;HUANG Zhiping;SU Shaojing
    J4. 2011, 38(6):  159-162+172.  doi:10.3969/j.issn.1001-2400.2011.06.026
    Abstract ( 1475 )   PDF (655KB) ( 1305 )   Save
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    In order to get the error-correcting codes information of the unknown lines in digital communication, a novel method of fast detection BCH generator polynomial is presented. The length of binary primitive BCH codes is recognized by the roots information dispersion entropy idea. Then, on the basis of the isomorphic principle of finite fields, the BCH generator polynomial is gained directly through multiplication and simplification in finite fields with the roots obtained before. The novel method can avoid the calculational and temporal complexity brought by searching the primitive polynomial in the existing algorithms observably. The experimental result shows that the fast recognition method is valid.

    Research on some important constants of the arithmetic-geometric sequence
    LIANG Changhong;SHI Yan
    J4. 2011, 38(6):  163-166+192.  doi:10.3969/j.issn.1001-2400.2011.06.027
    Abstract ( 954 )   PDF (403KB) ( 953 )   Save
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    Some arithmetic-geometric sequences consisting of the important constants including not only the ratio of circumference π and exponential e but also Euler constant γ and nonlinear chaos point k are discussed. The phenomenon that without exception these arithmetic-geometric sequences approach the constant values as n increases has been deeply studied. The best approximations of the rational fraction to these important constants are given.

    An Electromagnetism-like Mechanism Algorithm Based On Good Point Set
    JIANG Jianguo;LONG Xiuping;TIAN Min;LI Jin
    J4. 2011, 38(6):  167-172.  doi:10.3969/j.issn.1001-2400.2011.06.028
    Abstract ( 1331 )   PDF (466KB) ( 907 )   Save
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    The electromagnetism-like mechanism(EM) algorithm is a new heuristic algorithm for global optimization. By analyzing the optimization mechanism of EM, an improved Electromagnetism-like Mechanism algorithm, which is an Electromagnetism-like Mechanism algorithm based on the good point set, is proposed. The new algorithm constructs the initial population by using the principles of the good point set in the number theory, and improves the local search algorithm. This algorithm calculates the total force vector between particles by using the modified equation, and designs an adaptive move operator to update the location of those particles. Experimental results show that the improved algorithm can converge to the global optima more effectively and accurately.

    Novel CUSUM spectrum sensing algorithm in cognitive UWB
    SONG Xiao'ou;XIANG Xin;BI Duyan;CHEN Shunfang
    J4. 2011, 38(6):  173-178.  doi:10.3969/j.issn.1001-2400.2011.06.029
    Abstract ( 1501 )   PDF (564KB) ( 914 )   Save
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    A novel Cognitive UWB spectrum sensing algorithm is proposed and evaluated, which enables the detection of the low average SNR and low duty ratio signal with low complexity and small detection delay. An uniform probability density function of the low duty ratio received signal is constructed based on the characteristic of the UWB pulse signal. CUSUM test is introduced to implement the detection. Theoretical analysis indicates that the proposed algorithm is suitable for low duty ratio signal detection. Compared with the energy detection algorithm, the proposed algorithm conquers the SNR wall phenomenon, with superior detection delay performance. Furthermore, the theoretical analysis results are proved by simulations.

    Design and implementation of a 3-D smooth mobility model
    ZHENG Bo;ZHANG Hengyang;HUANG Guoce;CHU Zhenyong;WANG Yequn
    J4. 2011, 38(6):  179-184.  doi:10.3969/j.issn.1001-2400.2011.06.030
    Abstract ( 1745 )   PDF (699KB) ( 1038 )   Save
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    Based on an introduction to the advancement of research on the entity and group mobility models of mobile Ad hoc networks, a novel three dimensional (3-D) smooth Gauss-semi-Markov mobility model for the 3-D mobile Ad hoc networks is proposed. Characterizing the Speed Up, Smooth, Turning, Disbanding, Assembling, Slow Down and Pause phases in the motion of nodes accurately, the model can truly reflect the physical law of moving objects in 3-D space. Furthermore, as the parameters in the model are more controllable than others, the model can be used flexibly as not only an entity model but also a group one by adjusting the parameters. Thus,the model can be applied for simulating node mobility in 3-D mobile Ad hoc networks.

    Degradation process simulation model and its use in image enhancement
    LI Quanhe;BI Duyan;HE Linyuan
    J4. 2011, 38(6):  185-192.  doi:10.3969/j.issn.1001-2400.2011.06.031
    Abstract ( 1450 )   PDF (5154KB) ( 1102 )   Save
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    In order to direct image enhancement better, we propose a Degradation Process Simulation Model by simulating the process of image degradation, mutual effects from adjacent pixels, not well-proportioned illumination, as well as the decline of the medium transfer ratio, are taken into account in the new model. A vision adaptability solution for the model is proposed according to the human visual system, including contrast sensitivity, brightness adaptive faculty and lateral inhibition. There are three processes in the solution: Firstly, deconvolution is applied to eliminate the adjacent pixels' mutual effects and upgrade the details; secondly, intensity adjustment is applied to gloom the bright area, brighten the dark area and balance illumination; thirdly, extra lightness removal is applied to recover the image's color and details, and then get the visual pleasing image. Compared with some preexisting image enhancement algorithms, it can be found in experimental results that the applications of the proposed algorithm yield some promising results in getting more details, upgrading the contrast, and having better visual pleasing characters.

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