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    20 October 2014 Volume 41 Issue 5
      
    Original Articles
    Reduced state demodulator for the SOQPSK-TG signal
    SUN Jinhua;HAN Huimei;ZHU Jili
    J4. 2014, 41(5):  1-6+12.  doi:10.3969/j.issn.1001-2400.2014.05.001
    Abstract ( 755 )   PDF (539KB) ( 1014 )   Save
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    To solve the problem of high complexity in the demodulator for a partial-response version of shaped-offset quadrature phase-shift keying(SOQPSK-TG), a simplified two-state demodulator for non-recursive SOQPSK-TG using the survivor path is proposed based on the decision feedback simplified demodulator of recursive SOQPSK-TG. First, a two-state trellis is deduced by proper state merging based on the four-state trellis of non-recursive SOQPSK-TG. Then, the simplified two-state trellis is used as the state transition trellis in the receiver to demodulate the received signal, and during the demodulation the hypothesized signal of each branch is obtained via the survivor path. Simulation results show that non-recursive SOQPSK-TG has a better performance than recursive SOQPSK-TG in the low SNR region, and the simplified two-state demodulator of non-recursive SOQPSK-TG has 0.5~1.0dB SNR degradation compared with the four-state demodulation algorithm; however the low computation complexity is beneficial to engineering application.

    Identity-based privacy-preserving multi-receiver key encapsulation
    FU Xiaotong;XUE Peng
    J4. 2014, 41(5):  7-12.  doi:10.3969/j.issn.1001-2400.2014.05.002
    Abstract ( 756 )   PDF (453KB) ( 887 )   Save
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    Anonymity can protect the privacy of the user. Based on the bilinear pairing, an efficient identity-based privacy-preserving multi-receiver key encapsulation mechanism is presented to protect the identities of the users who are able to access protected contents. This proposed scheme uses the one-way anonymous key agreement protocol and Hash function to generate the temporary key. In the random oracle model, we formally prove that the proposed scheme is confidential and anonymous under selective ID and chosen ciphertext attack. Besides, it has a higher efficiency and a shorter ciphertext.

    Design of bilayer lengthened LDPC codes for decode-and-forward in relay channels
    LIU Yang;LI Jing'e;LI Ying
    J4. 2014, 41(5):  13-17.  doi:10.3969/j.issn.1001-2400.2014.05.003
    Abstract ( 654 )   PDF (520KB) ( 686 )   Save
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    The bilayer density evolution algorithm is always used to design bilayer lengthened LDPC codes for the decode-and-forward relay system. The general approach is to fix the lower variable degree distribution and then find an upper variable degree distribution, which has higher complexity. To solve this problem, the Gaussian approximation algorithm is proposed to implement the overall optimization for the lower and upper variable degree distributions. The proposed algorithm aims at maximizing the rates of the source-to-relay and the source-to-destination link simultaneously, which has lower complexity. Simulation results show that the gap between the convergence threshold and the theoretical limit of the proposed LDPC codes is smaller and that BER performance is almost the same as that of the ensembles obtained by bilayer density evolution.

    Novel PHD filter in unknown clutter environment
    LI Cuiyun;JIANG Zhou;JI Hongbing
    J4. 2014, 41(5):  18-23.  doi:10.3969/j.issn.1001-2400.2014.05.004
    Abstract ( 1105 )   PDF (570KB) ( 849 )   Save
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    Aiming at improving the poor performance of the Probability Hypothesis Density(PHD) filter when the clutter model and the prior knowledge are mismatched, a novel PHD filter into which we introduce the augmented state space and which is used under the unknown clutter circumstance is proposed in this paper. The proposed filter can distinguish the target state space and the clutter state space by the augmented state space. Using the estimate of the unknown clutter model from the measurement, the filter can avoid the tracking performance reduction caused by the improper model selection of the unknown clutter. Simulation results show that the proposed algorithm can achieve a stable tracking performance under the unknown clutter circumstance and a tracking accuracy equal to that of the conventional PHD filter used in the unknown clutter circumstance in the real-time context.

    Correlation-coefficient-summation detector for wideband radar moving targets
    WEN Xiang;LIU Hongwei;BAO Min
    J4. 2014, 41(5):  24-29+117.  doi:10.3969/j.issn.1001-2400.2014.05.005
    Abstract ( 636 )   PDF (585KB) ( 658 )   Save
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    A correlation coefficient summation detector under the Gaussian noise for wideband radar moving targets are presented. Fourier transformation is carried out to take the absolute value for the signals of wideband radar moving targets in the range-frequency domain in order to remove the phase item caused by target moving, and then the correlation coefficient of conjoint signals are computed. By the property that the conjoint range spread target signals possess a high relativity, the summation of correlation coefficients is used for detect. After analyzing the probability of the echo signal without targets under the Gaussian noise, the detect threshold setting of the correlation coefficient summation detector is given and theoretical analysis shows that the detector possesses constant false alarm rate (CFAR) performance. Computer simulation  shows that the correlation coefficient summation detector given in this paper can achieve 2dB performance improvement than the non-scatterer density dependent generalized likelihood ratio test (NSDD-GLRT) detector with the known Doppler steering vector at the 90% detection.

    Improved low-rank recovery method for sparsely sampling data in array signal processing
    YANG Dong;LIAO Guisheng;ZHU Shengqi;WANG Kai
    J4. 2014, 41(5):  30-35.  doi:10.3969/j.issn.1001-2400.2014.05.006
    Abstract ( 665 )   PDF (788KB) ( 827 )   Save
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    Matrix Completion (MC) theory can recover the under-sampled data in the array signal processing, further estimating the direction of arrival (DOA) as the fully sampled data does. However, it is required that the data should be under-sampled randomly in different snapshots which satisfy the randomness of MC theory. When some sensors are unsampled or broken in the whole observing time, the previous method would fail. To address this problem, a new processing method is proposed in this paper. The inner relationship among sensors is used, and then we reshape the signal vector in a single snapshort into an equivalent low-rank matrix, which can be recovered effectively by minimizing the nuclear norm. Simulation results validate the effectiveness of the proposed method. Meanwhile, the method can lower the noie power, and improve the performance of the DOA.

    TDOA location algorithm based on modified Newton iterations
    ZHU Guohui;FENG Dazheng;LI Jin;ZHOU Yan
    J4. 2014, 41(5):  36-41.  doi:10.3969/j.issn.1001-2400.2014.05.007
    Abstract ( 691 )   PDF (1169KB) ( 910 )   Save
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    For the divergence problem of traditional iterative process based location algorithms, a new modified Newton algorithm for the passive location from time differences of arrival (TDOA) is proposed. The proposed algorithm firstly reorganizes the nonlinear TDOA equations into pseudo-linear ones by using an auxiliary parameter, and a constrained weighted least-squares minimization is developed for the positioning problem instead of the Maximum Likelihood estimator. A modified Newton method based on eigenvalue modification is then applied to obtain the emitter position. In order to reduce the number of iterations, an appropriate iteration step size is computed via one-dimensional optimization by the quadratic interpolation method. Simulation results demonstrate the effectiveness of the proposed algorithm.

    Unambiguous estimation of the radial velocity of a moving target by the range frequency maximum likelihood method
    ZHANG Xuepan;LIAO Guisheng;ZHU Shengqi;GAO Yongchan;YANG Dong
    J4. 2014, 41(5):  42-47+104.  doi:10.3969/j.issn.1001-2400.2014.05.008
    Abstract ( 692 )   PDF (1549KB) ( 714 )   Save
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    The radial velocity of a moving target should be estimated unambiguously in the synthetic aperture radar-ground moving target detection system. Estimation performance of the conventional maximum likelihood method based on multi-channel would decline when the radial velocity approaches the maximum unambiguous velocity. To solve these problems, the ML estimation method based on the range frequency interferometric phase is proposed in this paper. Compared with the conventional method, the proposed method weakens the effect of probability density function spreading. The radial velocity can be estimated accurately even when it approaches the maximum unambiguous velocity. The effect of noise on radial velocity estimation is also analyzed from two aspects of correlation coefficient and interferometric phase, which can be reduced by increasing independent samples. Numerical and real data are processed to demonstrate the effectiveness of the proposed method.

    Isomerous multiple classifier ensemble via transformation of the rotating forest
    MAO Shasha;XIONG Lin;JIAO Licheng;ZHANG Shuang;CHEN Bo
    J4. 2014, 41(5):  48-53.  doi:10.3969/j.issn.1001-2400.2014.05.009
    Abstract ( 655 )   PDF (597KB) ( 1068 )   Save
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    In order to boost the diversity among individual classifiers of an ensemble, a new ensemble method is proposed that combines two different classifier models via a transformation of rotation forest, named by isomerous multiple classifier ensemble.Firstly, the original samples are transformed and divided by the rotating forest to obtain new samples.Then support vector machine with the high accuracy of classification or kernel matching pursuit with the speedy classification is selected as a basic classifier model based on a special proportion, the selected classifier is used to classify the new samples, and the predictive labels are obtained. Finally, the predictive labels given by two different models are combined to obtain the final predictive labels of an ensemble. Particularly, the proposed method achieves the complementarity of accuracy and speed by combining two different classifier models, and it is important that isomerous classifier ensemble improve the generalization error of an ensemble and increases the classification performance. According to the experimental results of classification for UCI datasets and remote sensing image datasets, it is illustrated that the proposed method shortens obviously the running time and improves the accuracy of classification, compared with an ensemble based on the single classifier model.

    Non-rigid registration of medical images based on local linear embedding and improved L-BFGS optimization
    LI Qi;JI Hongbing;ZANG Bo;LIU Jin
    J4. 2014, 41(5):  54-60.  doi:10.3969/j.issn.1001-2400.2014.05.010
    Abstract ( 568 )   PDF (4628KB) ( 659 )   Save
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    Non-rigid registration of medical images has become a challenging task in medical image processing and applications. In this paper, we propose a local linear embedding (LLE) and improved L-BFGS (limited-memory Broyden Fletcher Goldfarb Shanno) optimization based registration method. With abundant spatial information and good stability in noisy environment, the ordinal features are computed on different orientations to represent spatial information in medical images. For high dimensional ordinal features, the LLE algorithm is used for dimensionality reduction and the inverse mapping of LLE is used to fuse complementary information together. Then a hybrid entropy based similarity measure which integrates image intensity with ordinal feature is chosen as the registration function. Finally an improved L-BFGS algorithm is used to search for the optimal registration parameters. We evaluate the effectiveness of the proposed approach by applying it to the simulated brain image data. Experimental results show that the proposed registration algorithm is less sensitive to noise in images. Compared with some traditional methods, the proposed algorithm is of higher precision and better robustness.

    Design of hybrid filter banks with fractional delays using mixed norm performance measures
    WANG Wei;ZHANG Zijing
    J4. 2014, 41(5):  61-66+111.  doi:10.3969/j.issn.1001-2400.2014.05.011
    Abstract ( 532 )   PDF (711KB) ( 781 )   Save
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    A mixed norm performance measure is presented to design finite impulse response (FIR) digital synthesis filters of hybrid filter banks with fractional delays. The mixed norm performance measure is based on the peak value as well as the energy of the error signal. The FIR filters are designed to minimize the performance measure of a hybrid error system. This hybrid and multirate problem is reduced to a mixed norm optimization problem involving only the linear time-invariant, discrete-time system. The theory of linear matrix inequalities offers a tractable solution to such a synthesis problem. Numerical experiments show that the proposed approach yields a better performance compared to existing techniques.

    Method for detecting DRFM deception jamming based on LFM rate matching
    LU Yunlong;LI Ming;YAN Yan
    J4. 2014, 41(5):  67-73+134.  doi:10.3969/j.issn.1001-2400.2014.05.012
    Abstract ( 690 )   PDF (927KB) ( 787 )   Save
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    For detecting linear frequency modulated (LFM) active deception jamming, a novel approach is outlined based on LFM rate matching of the jamming harmonic components. Utilizing the harmonic effect generated from a digital radio frequency memory (DRFM), the feature of the harmonic spectrum is analyzed and an LFM rate base of the jamming is established first. Then the Fractional Fourier Transform (FrFT) is employed to detect LFM components in the radar echo when both the target echo and the jamming signal are co-existent in a range gate. After that the LFM rates of the detected LFM signal are estimated and compared with the LFM rate bank to achieve jamming detection. Validity of the method is verified by simulation results.

    Wide-band analysis using the modified IE-FFT and physical optical hybrid method
    Lü Zhengliang;GONG Shuxi;ZHANG Pengfei;CHEN Wenfeng;ZHAO Bo
    J4. 2014, 41(5):  74-78.  doi:10.3969/j.issn.1001-2400.2014.05.013
    Abstract ( 630 )   PDF (2481KB) ( 464 )   Save
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    A highly efficient computational electromagnetic technique based upon the well known PO formulation combined with the modified IE-FFT and adaptive Stoer-Bulirsch frequency-sampling method is applied to wide-band analysis of antennas radiating in the presence of electrically large conducting platforms. By interpolating Green's function and introducing the concept of empty groups, the modified single-level FFT algorithm which is based on the subdomain FFT acceleration is employed to reduce matrix storage and to accelerate all the matrix-vector multiplications in both the linear system for moments and the iterative solver. Otherwise, the correction of the near-interaction is avoided. For the frequency response of electric currents, the SB algorithm using the rational approximation solution and the recursive rules is utilized to achieve fast frequency sweeping. Due to the above modifications, the PO hybrid method utilizes fewer unknowns and requires less solution time. Numerical examples are given to verify its validity.

    Electromagnetism-like mechanism algorithm via dual chaotic search
    JIANG Jianguo;LIU Mengnan;LIU Yongqing;SU Qian;ZHANG Liyuan
    J4. 2014, 41(5):  79-83+147.  doi:10.3969/j.issn.1001-2400.2014.05.014
    Abstract ( 522 )   PDF (453KB) ( 616 )   Save
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    An improved Electromagnetism-like mechanism algorithm is proposed to overcome the drawbacks of the original EM algorithm, such as strong randomness of the initial population, low ability for local search and low efficiency in the movement according to the total force. The new algorithm generates the initial population with the disturbance factor and opposite learning mechanism, improves the local search algorithm with the double chaotic search method, and calculates the total force between particles with the modified equation. Besides, the algorithm is used to design an adaptive move operator for updating the locations of those particles. Experimental results indicate that the proposed algorithm has a better convergence effect and a higher solution accuracy.

    Comprehensive analysis of real-time alerts with attack strategy graphs
    LI Longying;LI Jinku;MA Jianfeng;JIANG Qi
    J4. 2014, 41(5):  84-90.  doi:10.3969/j.issn.1001-2400.2014.05.015
    Abstract ( 572 )   PDF (995KB) ( 730 )   Save
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    The causal relation based alert correlation approach causes split scenario graphs and cannot process massive alerts in time. To address this issue, a comprehensive analysis approach of real-time alerts with attack strategy graphs is proposed. First, it gets rid of the splitting of the attack scenario graph by introducing hypothesizing alerts to the alert correlation process. Second, it leverages a novel sliding window mechanism, which maintains a window for each type of attacks and determines the window's size according to both the time and number of the alerts. This new mechanism only introduces linear time complexity without sacrificing effectiveness. Third, the approach is extended to a comprehensive system to reconstruct attack scenarios, predict future alerts and fuse analytical results. Evaluation results indicate that our approach is effective and efficient.

    Measurement of human heart rate using finger pictures
    YANG Zengyin;MA Jianfeng;SUN Cong;HUANG Dejun;YE Chunxiao;LU Diqun
    J4. 2014, 41(5):  91-97.  doi:10.3969/j.issn.1001-2400.2014.05.016
    Abstract ( 764 )   PDF (1367KB) ( 1474 )   Save
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    On the smart phone, a phone camera is used to capture finger images to achieve heart rate measurements. First, we apply the spectrum division method to filter the collected finger images,and then use the weighted power density spectrum of the three pixel to calculate the PPG (PhotoPlethysmoGraphy), based on the information and its differences contained in the three pixels. Then we apply the peak detection method based on the detection of the separated PPG signal to measure the heart rate.Comparing the measured results and the standard results, the average error is 1.82%, and the correlation of the true value is greater than 90%, indicating the reliability of heart rate measurement on finger images. The application of the method can greatly facilitate the convenience of chronic disease monitoring.

    Wireless network access selection method with the non-cooperative game
    ZHAO Jing;LI Xinghua;XUE Feijie;MA Jianfeng
    J4. 2014, 41(5):  98-104.  doi:10.3969/j.issn.1001-2400.2014.05.017
    Abstract ( 617 )   PDF (498KB) ( 765 )   Save
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    The coexistence of various wireless access networks has been widely recognized in the next generation network. As a different network access form, how the clients at the instance of their needs will select the access network has become a widespread concern. For this problem, according to the noncooperation between different access networks and the noncooperation relationship between the access network and the clients, a non-cooperative game model based on the payoff function is established. On the basis of the multi-attribute decision theory, the model uses the gray correlation analysis method to normalize the performance parameters of the network, chooses the grey relation grade as the payoff function, compares and selects excellent networks which the clients can access. By solving the Nash equilibrium between the clients and excellent networks, the clients can access the appropriate network. Experimental results demonstrate that the method can effectively select the appropriate network according to the needs of the clients.

    Inverse derivation of the adjustment quantity of the distorted reflector antenna feed from a far field
    LIAN Peiyuan;DUAN Baoyan;WANG Wei;HU Naigang
    J4. 2014, 41(5):  105-111.  doi:10.3969/j.issn.1001-2400.2014.05.018
    Abstract ( 736 )   PDF (1261KB) ( 912 )   Save
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    Reflector surface deformation can be compensated by adjusting the feed position. Aiming at the shortcoming of the traditional method that the best-fit paraboloid(BFP) needs to get the accurate reflector deformation beforehand, a method for the determination of the feed adjustment quantity from a far field is presented in this paper. Based on the aperture field method, explicit expressions for the sensitiveness of a far field to best-fit parameters of the distorted reflector are established. Then the best-fit parameters and the far field are linked with an over-determined linear system of equations, and by measuring the far electric field, the reflector deformation can be approximately calculated by the singular value decomposition method, providing guidance for feed adjustment. There is no need to know the reflector distortion in advance in the proposed method. Simulation cases show the correctness of the proposed method and the validity of the compensation for reflector distortion.

    Form-finding of tensegrity structures based on IAFSA
    LIN Min;LI Tuanjie;JI Zhifei
    J4. 2014, 41(5):  112-117.  doi:10.3969/j.issn.1001-2400.2014.05.019
    Abstract ( 674 )   PDF (611KB) ( 788 )   Save
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    To solve the form-finding problem of large-scale and nonregular tensegrity structures, an improved artificial fish swarm algorithm (IAFSA) is proposed on the basis of the force density formation of a tensegrity structure. First, the equilibrium equations for a tensegrity structure are developed based on the force density method. Then, a set of appropriate values of force density is found by the IAFSA in the force density space to make the rank of the equilibrium matrix satisfy the required conditions. As a consequence, the equilibrium configurations of the tensegrity structure can be derived. Furthermore, by employing the position information of the current global best artificial fish and the behaviors of swallowing and leaping of the artificial fish, the IAFSA has a higher search efficiency. Moreover, the use of leaping behaviors of the artificial fish makes the IAFSA have the ability to find global extremums. With the expandable octahedron as an example, its form-finding problem is conducted by using the IAFSA. Experimental results indicate that the form-finding results of the IAFSA are reliable. Compared with the conventional artificial fish swarm algorithm, the IAFSA has a higher convergence precision and a better average optimum value.

    Image retrieval using stable interest points and Gabor wavelet
    YAN Yunyi;JIANG Shuai;GUO Baolong
    J4. 2014, 41(5):  118-123.  doi:10.3969/j.issn.1001-2400.2014.05.020
    Abstract ( 643 )   PDF (2264KB) ( 526 )   Save
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    A new image retrieval method based on stable interest points and texture feature is proposed. Firstly, the optimal Hessian derivative filter is used to detect the stable interest points in the image. After that, pseudo-Zernike moments defined on the neighborhood of stable interest points in the annular region are calculated. Then, the texture feature is extracted by the Gabor wavelet transform. Finally, the difference in pseudo-Zernike moment and texture feature among images is used to depict image similarity. Experimental results show that this method reduces the effects of the unstable points and improves the image retrieval accuracy effectively comparied with other retrieval methods based on interest points.

    Location of a blasted penetrator in the test range
    WANG Lixia;FU Xiaoning
    J4. 2014, 41(5):  124-128+172.  doi:10.3969/j.issn.1001-2400.2014.05.021
    Abstract ( 610 )   PDF (858KB) ( 637 )   Save
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    Aiming at the problem of locating a blasted penetrator in the test range, a method based on the changed detection technology is proposed. First, four synchronized geophones and a reused explosive source are used to record the stress waves twice, i.e., before the penetrator fire and after the fire. By deducting inherent steep reflections, the reflected signal resulting from the penetrator blasting cavity is obtained as the change in the stress waves, which could be used for locating the blasted penetrator in the test range. Then, the ellipsoid equation focusing on each geophone and the explosive source are uniquely determined based on the wave path. Finally, an improved Chan algorithm is used to solve the intersection point of the ellipsoid models, and the estimated position of the blasted penetrator. This approach is verified by simulation. This method has a certain guidance in practical measurement of a penetrator in the test range.

    Quality assessment of the laser disturbing image utilizing cross entropy
    LIU Fei;SHAO Xiaopeng;HAN Pingli;XIANGLI Bin;REN Meng
    J4. 2014, 41(5):  129-134.  doi:10.3969/j.issn.1001-2400.2014.05.022
    Abstract ( 558 )   PDF (2039KB) ( 657 )   Save
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    A method for assessing the quality of disturbed image uses the cross entropy of the image for the problem that the imaging-guided weapons are liable to suffer laser interference by combining with the principles of guided tracking and anti-jamming mechanism. It is on the basis of the concept of cross-entropy in information theory that the method is presented. Analyses of similarity between images before and after disturbing are made to decide the evaluation function which combines the advantages of cross-entropy and the process of image quality assessment. The validity of the function derived is analyzed theoretically and experimentally. Experimental results are presented, and the method for the quality assessment of the laser disturbed image based on cross entropy can accurately obtain the threshold when laser interference is successful, so it is widely applicable to laser disturbing image quality assessment.

    Physical model for the off current in amorphous silicon thin film transistors
    EN Yunfei;LIU Yuan;HE Yujuan;SHI Qian;HAO Yue
    J4. 2014, 41(5):  135-140.  doi:10.3969/j.issn.1001-2400.2014.05.023
    Abstract ( 629 )   PDF (591KB) ( 850 )   Save
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    A physical model for the off current in amorphous silicon thin film transistors is proposed. Firstly, an approximation for the band bending in the back interface as a function of the gate-source voltage is derived in the reverse subthreshold region, and then a current model due to electron conduction in the back channel is developed by considering the deep states. Secondly, a rate used to describe the escaping possibility of holes in the bulk a-Si:H layer is proposed based on the one-dimensional continuity equation. By considering the hole generation rate in the drain depletion region and the hole escaping rate in the bulk a-Si:H layer, a leakage current model due to hole conduction in the front channel is developed. The proposed model has been verified using the experimental data.

    Nonconvex image inpainting via balanced regularization approach
    WU Yulian;FENG Xiangchu
    J4. 2014, 41(5):  141-147.  doi:10.3969/j.issn.1001-2400.2014.05.024
    Abstract ( 675 )   PDF (8601KB) ( 564 )   Save
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    Real images usually have two layers, namely, cartoons and textures, both of these layers have sparse approximations under some tight frame systems such as curvelet, local DCTs, and B-spline wavelet. In this paper, we solve the image inpainting problem by using two separate tight frame systems which can sparsely represent the two parts of the image. Different from existing schemes in the literature which are either analysis-based or synthesis-based sparsity priors, our minimization formulation applies the nonconvex sparsity prior via the balanced approach. We also derive iterative algorithms for finding their solutions. Numerical simulation examples are given to demonstrate that our proposed nonconvex method achieves significant improvements over the classical l<sub>1</sub> sparse method and the variation TV method in image inpainting.

    Enhancing user privacy for personalized web search in big data
    KANG Haiyan;XIONG Li
    J4. 2014, 41(5):  148-154+160.  doi:10.3969/j.issn.1001-2400.2014.05.025
    Abstract ( 621 )   PDF (610KB) ( 736 )   Save
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    To solve the contradiction between leaking user privacy potentially existing in large data and enhancing the performance of personalized information retrieval, an anonyminzation method based on the differential privacy with p-link technology is proposed. First, we generalize quasi identifiers and add noise to meet the differential privacy requirements. This method can maximize the query accuracy of statistical database, while minimizing the probability of identification records. Secondly, they cluster to meet the p-link equivalence group by the similarity between user profiles, and we calculate weights and equivalence group centroid. Finally, we release anonymized data. Experimental results demonstrate that the method of integrating the characteristics of differential privacy and p-link does not change users' interests, and that it can protect users' privacy, but also ensures a personalized retrieval performance.

    Adaptive binary search polyline simplification algorithm for GPS trajectories
    WANG Jing;TAN Xiangshuang;SONG Xianfeng;WANG Chaoliang
    J4. 2014, 41(5):  155-160.  doi:10.3969/j.issn.1001-2400.2014.05.026
    Abstract ( 580 )   PDF (1047KB) ( 730 )   Save
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    This paper proposes an adaptive binary search polyline simplification algorithm for simplifying GPS trajectories, which adopts the optimal skeleton point conceptual model of the Sleeve-fitting algorithm to retain a maximum point reduction. Meanwhile, the innovating modifications of screening roughly and handpickedly are suggested to improve the efficiency of simplification process significantly: (1)Dynamically predicting the search step to determine quickly a search interval within which at least one skeleton point falls; (2)Applying a binary search in the search interval of the GPS trajectory to locate the optimal skeleton point. The GPS trajectories acquired in Huaibei City, China are used for testing polyline simplification. As a result, our proposed algorithm preserves the best shape characteristics with a shortest running time.

    Out-of-core computing method of the adaptive cross approximation algorithm
    WU Junhui;LIANG Changhong;YUAN Haobo;CAO Xiangyu
    J4. 2014, 41(5):  161-165.  doi:10.3969/j.issn.1001-2400.2014.05.027
    Abstract ( 724 )   PDF (718KB) ( 734 )   Save
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    In order to solve computer memory limitation when computing the scattering characteristic of an electrically large target, the out-of-core adaptive cross approximation algorithm is designed. The adaptive cross approximation algorithm is used to compress the impedance matrix and reduce the computation complexity and storage effectively. By the use of the out-of-core technology, the memory space is reduced further and the calculating power of a single computer is raised by this method. The validity and effectiveness of the method are testified by numerical examples. lt is proved that the memory and computing time is reduced by this method when solving the radar cross section of a large target without losing the accuracy of the moment method.

    Robust beamforming algorithm for general signal models based on the ULA
    LIU Chengcheng;DING Yongchao;ZHAO Yongjun;YANG Jing2
    J4. 2014, 41(5):  166-172.  doi:10.3969/j.issn.1001-2400.2014.05.028
    Abstract ( 644 )   PDF (717KB) ( 699 )   Save
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    For the robust adaptive beamforming problem of incoherently scattered signals,a robust beamforming algorithm for general signal models based on the uniform linear array (ULA) is proposed. By introducing the conjugate data rearrangement method, two transformation matrices are defined to reconstruct the signal covariance matrices. Based on the new signal covariance matrices, the proposed algorithm gives a real valued close-form solution for the optimum weight vector to reduce the computational complexity. Then, the influences of the Signal-Noise-Ratio, snapshots, look direction errors and mismatch constraint parameters on the output Signal-Interference-Noise-Ratio are discussed in detail. The conjugate data is rearranged and reused in the new covariance matrix,so that the performance is obviously improved under the conditions of a limited number of snapshots, the severe signal mismatch and so on. Simulations illustrate the effectiveness of the proposed method.

    Cryptanalysis of the LBlock using multiple zero-correlation linear approximations
    LUO Fang;ZHOU Xueguang;OU Qingyu
    J4. 2014, 41(5):  173-179.  doi:10.3969/j.issn.1001-2400.2014.05.029
    Abstract ( 673 )   PDF (866KB) ( 777 )   Save
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    In order to reduce the data complexity of zero-correlation linear cryptanalysis of the LBlock, cryptanalysis of the LBlock using multiple zero-correlation linear approximations is presented. 2<sup>6</sup> zero-correlations for 14 the round LBlock is proven, and its construction is given. The normal distribution probability model is applied to attack the 22 round LBlock, with the 2<sup>6</sup> zero-correlations for the 14 round LBlock used as the distinguisher. The data complexity of the cryptanalysis is about 2<sup>63.45</sup> known plaintexts, the computing complexity is about 2<sup>76.27</sup>, and the success probability is 0.85. It is proved that the problem that the whole plaintext is needed to cryptanalyze the LBlock is solved.

    Analysis of dynamic reliability of the repairable k-out-of-n system under several times random shocks
    FANG Yongfeng;CHEN Jianjun;CAO Hongjun
    J4. 2014, 41(5):  180-184+206.  doi:10.3969/j.issn.1001-2400.2014.05.030
    Abstract ( 674 )   PDF (436KB) ( 713 )   Save
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    The model of unit dynamic reliability of the reparable k-out-of-n system is given under several times random shocks with the strength of unit degradation according to the strength-stress theory and the unit failure probability can be observed by using the dynamic reliability. The unit failure number can be obtained under several times random shocks according to the unit failure probability. The conversion probability of the reparable k-out-of-n system is given by its Markov property under several random shocks. The probability density matrix is observed by the conversion probability, and then the dynamic reliability of the reparable k-out-of-n system is obtained by solving the differential equation systems. Finally, it is illustrated that the method is prachcable and convenient. The calculated result conforms to the engineering practice.

    Universally composable security authenticated key exchange protocol
    ZHANG Zinan;GUO Yuanbo;YANG Kuiwu;HUANG Huixin;YANG Zhanhai
    J4. 2014, 41(5):  185-191.  doi:10.3969/j.issn.1001-2400.2014.05.031
    Abstract ( 663 )   PDF (530KB) ( 752 )   Save
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    The Physical Unclonable Function(PUF) is a physical unclonable process function which refers to inputing a challenge to a physical entity,which uses its inevitable changes in the physical details to output a random unpredictable response.To solve the issue of the limited computing, storage and communication capabilities of sensor nodes, according to the analysis of the PUF, a physical unclonable function system(PUFS) framework is defined, and based on this framework, a new Key Exchange protocol is proposed. Finally, a security analysis of our PKE protocol in the universally composable (UC) framework is given in detail. Compared to the traditional public key encryption KE scheme, the PKE protocol does not use any computational assumptions but rather the secure property of the PUFS, and thus our scheme needs less computation and communication cost.

    Improvement on three-dimensional reconstruction of the attention mechanism
    LI Minning;ZHANG Qiao;ZHAO Jie
    J4. 2014, 41(5):  192-196.  doi:10.3969/j.issn.1001-2400.2014.05.032
    Abstract ( 688 )   PDF (2439KB) ( 478 )   Save
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    In 3D reconstruction, from the aspects of feature extraction, in the feature extraction process with human visual attention mechanism simulation, the higher significant target is given more attention. The extracted features are selected, and the information quantity is reduced. The purpose is to reduce the computational burden of the computer, and improve the reconstruction efficiency.

    Heterogeneous data synergistic location method in the WSN
    XING Tianzhang;WANG Ju;CHEN Xiaojiang;FANG Dingyi;YANG Zhe
    J4. 2014, 41(5):  197-202.  doi:10.3969/j.issn.1001-2400.2014.05.033
    Abstract ( 627 )   PDF (1132KB) ( 670 )   Save
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    For the passive localization problem, a novel method called the heterogeneous data synergistic (HDS) based on the dynamic Bayesian network is proposed, which can coordinate heterogeneous data, and localize the target in the wireless sensor network (WSN). By comprehensively analyzing the three localization models (the signal strength model, the infrared ranging model and the particle filter) in the WSN, their characteristics are summarized in brief. According to the Bayesian network and the different characteristics, the HDS is designed under the dynamic deduction. Simulation results prove that the proposed method is adequate to the passive localization, and that compared with other traditional methods, the localization accuracy is greatly improved.

    Wide frequency-regulated Precision OCXO
    BAI Lina;ZHOU Wei;REN Junqi
    J4. 2014, 41(5):  203-206.  doi:10.3969/j.issn.1001-2400.2014.05.034
    Abstract ( 607 )   PDF (453KB) ( 634 )   Save
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    When precision standard frequency control devices are used, we always need controllable crystal oscillators that not only can be regulated in a wide frequency range, but also can maintain high frequency stability and low phase noise. In order to realize the wide frequency range, we have to use the crystal oscillator which shows good pull ups, but at the same time poor frequency stabilities and aging. High precision Oven-Controlled Crystal Oscillator(OCXO) based on SC cut overtone crystals can show very high frequency stability and low aging. However, its frequency regulation range by voltage control is not wide. When it is phase locked and controllable, it can not be used. In connection with a wider frequency regulation range, a new method is proposed through the regulation of the control temperature of the OCXO. In this way, all the good performances of the precision OCXO can be kept, and the original 10<sup>-7</sup> order voltage-controllable frequency range is improved to 5×10<sup>-6</sup> or even wider at the same time. Then it can be used in the frequency source which needs to be stably locked for a long time such as an on-board atomic clock,to ensure the stable and excellent indexes of the system.

    Tracking-before-detection method based on range extension for HPRF radars
    ZHANG Peng;ZHANG Linrang;HU Zijun
    J4. 2014, 41(5):  207-212.  doi:10.3969/j.issn.1001-2400.2014.05.035
    Abstract ( 656 )   PDF (600KB) ( 712 )   Save
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    Aiming at the issue of range ambiguity, a novel tracking-before-detection (TBD) method based on range extension is proposed for dim target detection with high pulse repetition frequency (HPRF) radars. The proposed method functioning in a staggering multiple pulse repetition frequencies (PRFs) mode preprocesses the MTD-processed data and performs range-extension according to different range ambiguous numbers. The maximum energy of targets is then acquired through the accumulation of energy inside the group of multiple PRFs and of tracking energy between groups. Finally, the track diffusion effect incurred by the dynamic programming algorithm is eliminated using the tracking cohesion strategy, and the tracking of fake targets caused by a low signal to noise ratio is reduced according to the correlation between fake and real targets. The new method improves the detection performance of the dim target without a priori knowledge of the state of the target. Simulation illustrates the effectiveness of the proposed method.

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