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    20 December 2014 Volume 41 Issue 6
      
    Original Articles
    Improved laplace mixed model potential function algorithm for UBSS
    FU Weihong;WANG Lu;MA Lifen
    J4. 2014, 41(6):  1-5+88.  doi:10.3969/j.issn.1001-2400.2014.06.001
    Abstract ( 828 )   PDF (548KB) ( 804 )   Save
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    Aiming at the problem that the original Laplace Mixed Model Potential Function(LMMPF) algorithm  has high complexity and the random initial cluster center algorithm has a low accuracy and stability, we propose an improved LMMPF algorithm. Based on the concept of density, we can choose some high-density data as the initial cluster centers. These data obey the principle that the distance between the data in the same group is small and the distance between groups is great. Theoretical analysis and experimental results show that compared to the original LMMPF algorithm the complexity of the new algorithm becomes much lower while the estimated accuracy is reduced only a little bit. When the Signal to Noise Ration(SNR) is 10dB, the running time of the improved algorithm is reduced to 5%. Compared to the randomly-chosen algorithm, the new algorithm has a much higher accuracy: the accuracy rate of estimating the number of sources is raised from 61% to 85% and the mixing matrix estimated error is reduced from 0.47 to 0.27.

    Method for the response model of the RC chain circuit
    REN Peng;XIANG Zheng
    J4. 2014, 41(6):  6-11.  doi:10.3969/j.issn.1001-2400.2014.06.002
    Abstract ( 637 )   PDF (752KB) ( 709 )   Save
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    A fast and efficient model is constructed for the RC chain circuit to output the responses of all nodes each time. Concretely, the relationship between input and output voltage related to nodes is derived by using the circuit principle in the time-domain, and then the output responses of the RC chain circuit are gradually calculated in a mathematical way. Experimental results demonstrate that the proposed model has a good performance with a predicted accuracy and propagation delay and its computational complexity reaches a low level.

    Cross-range scaling for ISAR imaging within short CPI and low SNR
    CHEN Qianqian;XING Mengdao;LI Haolin;BAO Zheng
    J4. 2014, 41(6):  12-17+64.  doi:10.3969/j.issn.1001-2400.2014.06.003
    Abstract ( 678 )   PDF (2314KB) ( 403 )   Save
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    This paper proposes a new algorithm for solving cross-range scaling for the inverse synthetic aperture radar(ISAR) imaging during a short Coherent Processing Interval (CPI) under a low Signal Noise Ratio (SNR). Based on the sparsity characteristic of the ISAR image, a Weighted Compressive Sensing (WCS) procedure is applied to generate high-resolution images, which can encourage signal components while suppressing noise. Then on the basis of the characteristics of 2-D Fourier transform (2-D FFT) and polar mapping, the Rotation Angle Velocity (RAV) initial estimation is realized by the correlation between two polar images. Finally, the maximum correlation position is found by using WCS, improving the estimation precision and efficiency of RAV. The rescaled ISAR image can be implemented. Both simulated and real-measured data confirm the feasibility and effectiveness of the proposed algorithm.

    Novel polarimetric target signal reconstruction method jointed with attributed scattering centers
    DUAN Jia;XING Mengdao;ZHANG Lei;WANG Jinwei;LIANG Yi
    J4. 2014, 41(6):  18-24.  doi:10.3969/j.issn.1001-2400.2014.06.004
    Abstract ( 777 )   PDF (3808KB) ( 355 )   Save
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    Traditional polarimetric target decomposition (PTD) methods decompose the scattering mechanism of every pixel into a weighted sum of basic scattering mechanisms, in which the whole feature of assemblies can hardly be revealed. Moreover, the man-made targets are frequently of low signal-to-noise ratios. Directly applying the PTD methods can hardly reveal the real scattering mechanism of targets. Therefore, the fully polarimetric attributed scattering center model is brought in to decompose the target signal into a set of classical attributed scattering centers to preserve integral properties. Moreover, the parameter is estimated with a high anti-noise property by joint polarization. Based on these, a novel polarimetric target signal reconstruction method jointed with attributed scattering centers is proposed in this paper. The proposed method is capable not only of reconstructing a target signal under low signal-to-noise ratios but also of preserving the integral properties of typical attributed scattering centers. As a result, the visualization of the polarimetric image has been improved effectively.

    Joint initialization of high-speed targets via multistatic passive-radar measurements and its tracking algorithm
    HU Zijun;ZHANG Linrang;ZHAO Shanshan;WANG Jingli
    J4. 2014, 41(6):  25-30+110.  doi:10.3969/j.issn.1001-2400.2014.06.005
    Abstract ( 650 )   PDF (585KB) ( 681 )   Save
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    A new extension of the sequential Monte Carlo multiple-model probability hypothesis density (SMC-MMPHD) filter is presented in order to track multiple high-speed maneuvering targets via passive coherent location (PCL) radar. With the standard MMPHD filter it is assumed that the target birth intensity is known a priori, but in PCL radar where the targets can appear anywhere in the surveillance volume and the velocity range is wide, this is clearly inefficient. The extension enables us to adaptively initialize the new targets at each scan using the localization results of the measurements which are far away from the current estimated multi-target states and to effectively track multiple high-speed maneuvering targets. Simulation results show that the proposed method is viable.

    Novel particle filter algorithm based on evolution fission
    WANG Zeyu;LI Ming;ZHANG Peng
    J4. 2014, 41(6):  31-36+75.  doi:10.3969/j.issn.1001-2400.2014.06.006
    Abstract ( 730 )   PDF (1221KB) ( 570 )   Save
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    In order to overcome the choice of the importance function and the sample impoverishment after resampling, an improved particle filter algorithm based on evolution fission is presented. The algorithm uses the UKF to generate the importance function and updates the samples based on evolution fission, which could increase the diversity of the samples and overcome the degeneration of the typical particle filter. Simulation results prove that the presented algorithm has a high tracking accuracy and a good tracking performance compared to the typical particle filter.

    Interacting multiple model box particle filter with quantitative measurements
    ZHAO Xuegang;SONG Liping;JI Hongbing
    J4. 2014, 41(6):  37-44.  doi:10.3969/j.issn.1001-2400.2014.06.007
    Abstract ( 683 )   PDF (596KB) ( 642 )   Save
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    In the distributed multi-sensor networks, in order to save the communication bandwidth,  to quantize the point observations obtained by sensors into the interval measurements is required. However, the traditional filtering algorithm can not directly deal with the quantitative measurements. The box particle filter (Box-PF) as a "generalized particle filter" algorithm uses the box particles and the bounded error model to replace the traditional point particles and the error statistical model. Therefore, it is a powerful tool for processing interval measurements. Key advantages of the Box-PF against the standard particle filter (PF) are a smaller particle number,  reduced computational complexity and a fast running speed. Therefore, to cope with the maneuvering target tracking with the quantitative measurements, this paper presents an interacting multiple model box particle filter (IMMBPF) algorithm. Simulation results show that under the condition of quantitative measurements IMMBPF and IMMPF are both able to accurately estimate the states of the maneuvering target. The IMMBPF, however, needs fewer particles, and computes more efficiently.

    Novel Pan-sharpening method via an optimal intensity component
    LIU Fan;ZHANG Kai;JIAO Licheng;YANG Shuyuan
    J4. 2014, 41(6):  45-50.  doi:10.3969/j.issn.1001-2400.2014.06.008
    Abstract ( 724 )   PDF (6770KB) ( 460 )   Save
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    The traditional Pan-sharpening method based on Intensity-Hue-Saturation transform leads to the spectral distortion problem. In this paper, a novel method is proposed for achieving the optimal intensity component to overcome this problem. According to the intensity component of the panchromatic image, the proposed method provides a global optimal weight for each single spectral image by using the Clone Selection Algorithm, which reflects the compromise proportion of each single spectral image and releases the spectrum correlation. The optimal intensity component constructed based on these weights acts actually as the panchromatic image. Using the ARSIS frame, the high-frequency information on the optimal intensity component is replaced by that of the panchromatic image to reconstruct the multi-spectral images with a high resolution by the inverse IHS. Experimental results on the data from the satellite QuickBird validate that the proposed method is effective in releasing the spectral distortion problem and enhancing the detailed information in the multi-spectral satellite images. The fused spectral images are of both high spatial resolution and low spectral distortion.

    Moving target detection for airborne radar under repeater jamming environment
    WU Yifeng;WANG Tong;WU Jianxin
    J4. 2014, 41(6):  51-56+154.  doi:10.3969/j.issn.1001-2400.2014.06.009
    Abstract ( 690 )   PDF (570KB) ( 634 )   Save
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    Repeater jamming brings a great challenge to moving target detection for airborne radar. It not only causes a false alarm but also raises the threshold of the detector, which reduces the probability of detection. A method based on maximum likelihood estimation to detect a moving target for airborne radar under repeater jamming environment is proposed. Firstly, the spatial steering vector of repeater jamming is estimated. Afterward, the maximum likelihood method is utilized to estimate the amplitude of the target, whose estimated amplitude is used to detect the moving target. Simulations show that this method is capable not only of suppressing the clutter but also of reducing the effect of repeater jamming from the sidelobe on moving target detection. Moreover, it can reduce the effect of repeater jamming from the mainlobe to a certain degree.

    Programmable mlti-phase clock circuit with delay calibration
    LIU Shubin;ZHU Zhangming;ZHAO Yang;EN Yunfei;LIU Lianxi;YANG Yintang
    J4. 2014, 41(6):  57-64.  doi:10.3969/j.issn.1001-2400.2014.06.010
    Abstract ( 773 )   PDF (2434KB) ( 472 )   Save
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    Based on the principle of the delay-locked loop (DLL), this paper introduces a programmable multi-phase clock circuit with a delay calibration loop. The proposed circuit offers a clock signal with a precision of 390ps and optimum timing for a variety of CCD signal processors. One cycle of the main clock is divided into 32 parts equally, while timing with a tunable duty cycle is generated by the programmable phase combiner. The increase in delay elements worsens the delay time error between different phases of the output signals, and hence a delay time calibration loop is applied to suppress this effect. In SMIC 0.18μm 3.3V CMOS process, with a 80MHz main clock, the post simulation results show that the proposed circuit generates an output clock with a 2%~98% duty cycle, a 1.14ps edge to edge jitter and a less than 5ps calibrated delay time error.

    Temperature monitor suitable for UHF RFID
    QI Zengwei;ZHUANG Yiqi;LI Xiaoming;LIU Weifeng;ZHANG Yanlong;REN Xiaojiao
    J4. 2014, 41(6):  65-70.  doi:10.3969/j.issn.1001-2400.2014.06.011
    Abstract ( 683 )   PDF (2003KB) ( 708 )   Save
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    A temperature monitor, suitable for UHF RFID, which adopts a double voltage controlled oscillator (VCO) structure, is designed. The monitor can be used in environment temperature detection and in the supply chain. The output of the monitor is related with temperature only, for the impact of the process and supply voltage variation on the absolutely same VCOs can be counteracted. As the time divided module is adopted, the monitor will be shut down after the temperature is detected. In this module, the problem of recounting can be avoided, and the work range of the tag is not reduced. The design was implemented in SMIC 0.18μm 2P4M EEPROM process. The read and write range of the tag is 6m and 2.5m respectively. And the temperature error is less than ±1.5℃ during the range of-40℃~+85℃ with an accuracy of 0.5℃.

    Design of a retrodirective array for RFID application
    CHEN Lei;SHI Xiaowei;YU Jianfeng;CHEN Yang
    J4. 2014, 41(6):  71-75.  doi:10.3969/j.issn.1001-2400.2014.06.012
    Abstract ( 659 )   PDF (1382KB) ( 602 )   Save
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    A C-band retrodirective array is presented. A single antenna is designed for both receiving and retransmitting where the isolation is provided by the hybrid coupler. The heterodyne technique is used for the phase-conjugation process which is achieved by a passive field effect transistor(FET) mixer with a shared input/output port. The proposed array has the characteristics of low cost, compact size, high isolation and long working distance. A four-element prototype is demonstrated with an interrogating frequency of 5.81GHz and a local oscillator frequency of 11.6GHz. Measured results verify that the system has good retrodirectivity over an incident range of ±33° which is suitable for radio frequency identification(RFID) application.

    Pi-calculus modeling for the multi-Agent collaborative system
    YU Bin;ZHANG Chen;LI Weijing
    J4. 2014, 41(6):  76-82.  doi:10.3969/j.issn.1001-2400.2014.06.013
    Abstract ( 700 )   PDF (722KB) ( 617 )   Save
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    With features of autonomy and reactivity, MAS is suitable for large complex distributed systems. For analyzing and simulating the collaborative process of multiple Agents, which is a concurrent job, and for achieving the reasonable system, Pi calculus is used to model MAS. This paper gives three kinds of Agent communication model in the Multi-Agent collaborative system, named broadcast, matchmaker and broker. And then it describes the Pi calculus models of the interactions between the Agents. Choosing the Home Networking System as a Multi-Agent collaboration instance, the author makes use of Pi calculus to modeling and simulation of multiple Agents collaborative communication. Finally, the verification of the semantics of the model is made with the Mobility Workbench, demonstrating that Pi calculus is suitable for MAS modeling.

    SVM decision-tree multi-classification strategy via electromagnetism-like mechanism
    JIANG Jianguo;ZHAO Yuan;MENG Hongwei;LI Bo
    J4. 2014, 41(6):  83-88.  doi:10.3969/j.issn.1001-2400.2014.06.014
    Abstract ( 624 )   PDF (566KB) ( 556 )   Save
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    Based on the characteristics of the classification problem, a modified electromagnetism-like mechanism (EM) algorithm is designed, which is suitable for classification. Then a modified EM-based optimal decision-tree algorithm is proposed to deal with the SVM multi-class classification problem. First, EM is used to create an optimal or near-optimal decision tree automatically, which makes the margin between two classes maximal at every decision node. Then at every decision node, standard SVM is used to make binary classification. Finally, the SVM decision tree achieves multi-classification. Experimental results show that the proposed method is better than the traditional methods such as “1-a-1”, “1-a-r”, “DAG-SVM”,“DT-SVM” and “GADT-SVM”.

    New ranking method for many-objective problems
    DAI Cai;WANG Yuping;HE Xiaoguang
    J4. 2014, 41(6):  89-94.  doi:10.3969/j.issn.1001-2400.2014.06.015
    Abstract ( 717 )   PDF (830KB) ( 697 )   Save
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    A new ranking method is proposed to solve many-objective optimization problems. It can be used to generates many approximate optimal objective vectors to increase the size of population, so that the individuals can be efficiently sorted by using non-dominance sorting. An ideal Pareto Front is first constructed, and then the ideal Pareto Front is divided into a number of grids. For each individual, it is uniquely assigned to a grid, and then some nodes of the grid are used to determine whether the individual is a non-dominance solution. Experimental results show that, even for 50-objective optimization problems, the convergence measurements of solutions obtained by the ranking method are smaller than 1. Meanwhile, compared with two state-of-the-art relaxed forms of Pareto dominance, the experimental results show that this ranking method can simultaneously maintain the diversity of solutions and have good convergence.

    Novel cluster refinement algorithm for DNA motif discovery
    ZHANG Yipu
    J4. 2014, 41(6):  95-99.  doi:10.3969/j.issn.1001-2400.2014.06.016
    Abstract ( 694 )   PDF (445KB) ( 581 )   Save
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    The motif discovery problem is an important aspect of the analysis of gene transcriptional regulatory relationship. This paper describes a novel entropy-based cluster refinement algorithm (ECRmotif) for motif discovery in DNA sequences. ECRmotif employs a flexible probabilistic model to identify motif from the background sequences. It first utilizes an entropy-based cluster process to divide the dataset into several subsets, and then reduces the instances searching space for each candidate subset and refines the motif from the candidate subsets. Experiments by using both synthetic and real datasets demonstrate that our algorithm increases the running speed and efficiency and finds motif accurately.

    Central force optimization algorithm via clustering simplex search
    LIU Jie;WANG Yuping
    J4. 2014, 41(6):  100-105.  doi:10.3969/j.issn.1001-2400.2014.06.017
    Abstract ( 614 )   PDF (472KB) ( 578 )   Save
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    An improved central force optimization (CFO) is proposed based on the clustering and simplex method for global optimization. The clustering simplex (CS) operator is introduced to a new algorithm in the evolution process. Vertices of simplex are selected by clustering methods, and a periodical migrating of the best individual is introduced by the CS operator. CS can get away from local converged points by virtue of CFO, and CFO can improve its local exploiting capability and effectively speed up the convergence under the help of CS. Experimental results show that the proposed hybrid CSCFO algorithm is better than other algorithms in convergent speed and searching precision.

    Precise integration method for the Gram matrix of time-invariant systems
    LI Sulan;REN Yuanhao;BAO Hong;ZHANG Wei
    J4. 2014, 41(6):  106-110.  doi:10.3969/j.issn.1001-2400.2014.06.018
    Abstract ( 611 )   PDF (442KB) ( 649 )   Save
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    The Gram Matrix is an important index for reflecting the structure characteristics of a linear time-invariant system. By analyzing the state equations for the linear time-variant system, the key idea of precise integration method(PIM), namely the addition theorem and incremental storage technology, is applied to solve the Gram Matrix. The specific calculation method is given and the exact solution is also obtained. The matrix inversion is not required, even when the system is singular or unstable, it can also be solved with high precision. Finally, two numerical examples are given to demonstrate the correctness and validity of the method.

    Topology optimization design of heat conduction structures with random variables
    YOU Fang;CHEN Jianjun;CAO Hongjun;XIE Yongqiang
    J4. 2014, 41(6):  111-117.  doi:10.3969/j.issn.1001-2400.2014.06.019
    Abstract ( 682 )   PDF (748KB) ( 649 )   Save
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    Topology optimization design of a heat conduction structure with random variables under dissipation of heat transport potential capacity constraint is discussed. The mathematical model of topology optimization, based on the probabilistic reliability index with dissipation of heat transport potential capacity constraint, is constructed. The total volume of heat conductive material is to be minimized and the relative thermal conductivity of elements is regarded as the design variable here. The computational expressions for numerical characteristics of dissipation of heat transport potential capacity based on the random factor method are presented. Evolutionary structural optimization method is used in optimization. A filtering technique is employed to eliminate numerical instabilities in process of topology optimization. Two numerical examples are presented to demonstrate the feasibility and effectiveness of the optimal model and the solution.

    Improved method on weights determination of indexes in multi-objective decision
    GUO Jinwei;PU Xuqiang;GAO Xiang;ZHANG Yongan
    J4. 2014, 41(6):  118-125.  doi:10.3969/j.issn.1001-2400.2014.06.020
    Abstract ( 878 )   PDF (477KB) ( 848 )   Save
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    In multi-objective decision, the problem of computing the weights of the indexes is usually considered In view of the shortcomings in the existing techniques, this paper proposes an improved weights determination method by the efficient combination of the entropy weight method (EWM) and the analytic hierarchy process (AHP). In the presented method, the amalgamation is firstly carried out between the objective weights of underlying indexes by EWM and the subjective weights of indexes on the sub-criterion level by AHP. The obtained weights of indexes are synthesized subsequently with the weights of upper indexes. After normalization, the final weights of indexes are obtained. The results show that the final weights by this presented method have higher reliability.

    Kinematics planning of flexible parallel robot system
    WANG Wenli;CAO Hongjun
    J4. 2014, 41(6):  126-130.  doi:10.3969/j.issn.1001-2400.2014.06.021
    Abstract ( 628 )   PDF (728KB) ( 518 )   Save
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    Aiming at the problem of the cabin's dynamic response and positioning accuracy of the Five-hundred-meter Aperture Spherical Telescope caused by the mutation of the cables speed, the kinematics planning method for the flexible parallel robot system is proposed. For accurately controlling the length and speed of cables at the same time, the heuristic strategy of robot joint planning theory is used to produce the cables speed data of discrete points. A hybrid algorithm combining the 3<sup>rd</sup> and 4<sup>th</sup> interpolation is proposed to achieve the continuous speed data and the continuous acceleration data between discrete points.The study result shows that the planning data of cables length and cables speed are smooth and that the interpolation accuracy satisfies the need of the Five-hundred-meter Aperture Spherical Telescope. This kinematics planning method can solve the problem of the cabin's dynamic response and the positioning accuracy caused by the mutation of the cable speed.

    Random cache placement strategy for content-centric networking
    HU Qian;WU Muqing;GUO Song;PENG Li
    J4. 2014, 41(6):  131-136+187.  doi:10.3969/j.issn.1001-2400.2014.06.022
    Abstract ( 829 )   PDF (680KB) ( 656 )   Save
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    Content-Centric networking (CCN) is a new network architecture, which has broken the traditional end-to-end communication mode and focuses on contents. In CCN, in-network caching can enhance content delivery on a global scale without requiring a special infrastructure. In this paper we propose a distributed random cache placement strategy, in which caching nodes are selected based on the distance to the content provider. Then the expression for the cache hit ratio is derived as functions of the content request rate, content popularity distribution and cache size in each node. Numerical analysis and simulations show that our strategy can improve the cache hit ratio and reduce average hops to get contents by 5.59%~6.86%.

    Time slot allocation method based on the sliding window for hybrid switching networks
    CUI Jingfei;YANG Kun;WANG Jinlin;BAO Minquan
    J4. 2014, 41(6):  137-141.  doi:10.3969/j.issn.1001-2400.2014.06.023
    Abstract ( 550 )   PDF (598KB) ( 554 )   Save
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    For solving the problem that the CBR services have a large transmission delay through the hybrid switching networks, a sliding window-based time slot allocation method is proposed, which can decide the packet transmission delay by determining the CBR packets' slot position in the switching network. This method strictly constraints the absolute interval in a smaller range between the input and output time slots to ensure the packets' smaller transmission delay. Simulation results show that compared with the random allocation method, the sliding window-based allocation method can reduce the transmission delay effectively and the switching cache capacity.

    Hot-zone based routing protocol for mobile social networks
    YU Lingfei;GONG Haigang;WANG Xiaomin
    J4. 2014, 41(6):  142-147.  doi:10.3969/j.issn.1001-2400.2014.06.024
    Abstract ( 674 )   PDF (595KB) ( 582 )   Save
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    Routing is a challenged task for mobile social networks which are typical delay tolerant networks with intermittent connectivity. However, mobile social networks have inherent properties of social structure and the nodes often behave regularly, which could be used to assist in making routing decision. In this paper, a Hot-zone based Routing protocol is presented based on the hot-zones due to preference location the nodes visit and the regular mobility of the nodes. HRP forwards data based on the frequency of the visiting zone of the nodes. The higher the visiting frequency of the nodes is, the higher the probability of meeting the destination node is. Simulation results show that the average data delivery ration of HRP is 10% higher than that of BUBBLE with 30% less data transmission.

    Dimensions estimating and the dimension-reducing algorithms for the adaptive multi-dimension division code
    LI Zhijin;ZHOU Jie;QIAO Jie;WU Wenjuan
    J4. 2014, 41(6):  148-154.  doi:10.3969/j.issn.1001-2400.2014.06.025
    Abstract ( 557 )   PDF (492KB) ( 588 )   Save
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    When the dimension-weight(Q) equals the 4, Multi-Dimension Division Code algorithm is optimal. In this paper, we give the proof according to the principle of the Adaptive Multi-Dimension Division Code. The more the tags, the more the dimensions of the Multi-Dimension Division Code, and so we give the methods for tags estimation and dimensions estimation. Moreover, the algorithm for tags encoding after dimension-reduction is given, and the algorithm for tags decoding is given too. The Adaptive Multi-Dimension Division Code algorithm can significantly improve the efficiency of searching for tags whether in many collisions or few collisions.

    Speech enhancement method using self-adaptive time-shift and threshold discrete cosine transform
    ZHANG Junchang;LIU Haipeng;FAN Yangyu
    J4. 2014, 41(6):  155-159+194.  doi:10.3969/j.issn.1001-2400.2014.06.026
    Abstract ( 650 )   PDF (552KB) ( 628 )   Save
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    In view of the limitation of the existing speech enhancement methods under a low SNR, this paper proposes a speech enhancement method using self-adaptive time-shift and threshold discrete cosine transform. First, with the improved soft-threshold function to deal with the discrete cosine transform coefficients, we can not only eliminate the noise of noise-dominant frames, but also eliminate the noise of signal-dominant frames; the threshold is also selected self-adaptively based on the SNR, which can largely retain the original characteristics of the speech.Secondly, the shift of the analysis window is self-adapted according to the pitch period, reducing the white noise of the fixed window-shift.And a weighted autocorrelation function is introduced for pitch detection combined by the short-time autocorrelation function and the short-time average magnitude separation function, improving the precision of pitch detection and robustness to noise. Theoretical analysis and simulation results show that the output SNR of this method has increased greatly and the robustness to noise is better when the input SNR is as low as -5dB, compared with the empirical mode decomposition algorithm and the subspace algorithm.

    Non-rigid object tracking using joint matching of local features
    YU Wangsheng;HOU Zhiqiang;TIAN Xiaohua;ZHA Yufei
    J4. 2014, 41(6):  160-166.  doi:10.3969/j.issn.1001-2400.2014.06.027
    Abstract ( 782 )   PDF (4476KB) ( 409 )   Save
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    To the problem of non-rigid object tracking in video sequence, an efficient tracking algorithm based on joint matching of local features is proposed. The feature matching problem based on key points is translated into the optimization problem of balance assignment, and completed via joint matching of features under the maximization of holistic similarity. The tracking process is as follows. Firstly, local key points of the object template and current searching area are detected and described using the information on their neighborhoods. Then, the key points are marched via the proposed joint matching strategy, and the right matching pairs are picked out. Finally, the object's location and size are calculated according to the matching results, and the tracking result of the current frame is outputted. Experimental results indicate that the proposed algorithm is robust to object’s non-rigid deformation, and can cope with the complex background change to obtain a stable tracking result.

    Interact arithmetic of low-accuracy SINS' initial alignment and GPS orientation measurement with two antennas
    PANG Chunlei;ZHAO Xiubin;YU Yonglin;SONG Limei;WANG Zhuxin
    J4. 2014, 41(6):  167-173.  doi:10.3969/j.issn.1001-2400.2014.06.028
    Abstract ( 763 )   PDF (590KB) ( 633 )   Save
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    The low-accuracy strapdown inertial navigation system' (SINS) heading angle can not be achieved in the process of initial alignment, also the GPS direction finding with two antennas requires a long time for initialization. As to that, a new arithmetic is proposed in order to acquire the heading angle faster: the heading angle of the baseline is fixed quickly assisted by the baseline length in the condition of the least square error by searching the attitude; also the attitude is confined by elevation information from SINS' initial alignment. Then the heading angle is used in the SINS' initial attitude. The model is established, the principle of the new algorithm is discussed, and then some correlative expressions are induced. Experiments indicate that the new method proves proper and credible with simple algorithm and high practicability. The error is no more than 0.2°in pitch precision and yaw precision within 30 sec and initial alignment is accomplished within 100 sec.

    Improved multi-pattern matching algorithm
    CHU Yanjie;LI Yunzhao;WEI Qiang
    J4. 2014, 41(6):  174-180.  doi:10.3969/j.issn.1001-2400.2014.06.029
    Abstract ( 817 )   PDF (492KB) ( 759 )   Save
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    To resolve the problem that when the number of rules is large and the length of the shortest rule is short, the performance of the WM algorithm will become less efficient, the paper analyzes the WM algorithm and an improved algorithm named the QWM algorithm, then proposes a new algorithm—the SWM algorithm. The new algorithm uses the idea of the sub pattern set and optimizes the shifting and affirming method. To use the SWM algorithm in domain name filtering, a new hash function and a new matching order are designed specially. The results in domain name filtering indicate that the SWM algorithm's matching time is about 8.9%~11.6% that of the WM algorithm when the number of patterns is more than 10000. The SWM algorithm can improve the speed of matching when the scale of the pattern is large.

    Research on the access control model for multimedia social networks
    CHEN Qingli;ZHANG Zhiyong;XIANG Fei;WANG Jian
    J4. 2014, 41(6):  181-187.  doi:10.3969/j.issn.1001-2400.2014.06.030
    Abstract ( 682 )   PDF (788KB) ( 596 )   Save
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    Traditional access control models are not suitable for an emerging scenario of Multimedia Social Networks (MSNs), in which there are a large number of users, dynamic interaction and content sharing. The paper proposes an access control model for MSNs, based on users' major social relationships, such as relationship type, compactness, content sharing depth and trust. By the self-defined security rules and their security policies conflict elimination, the model effectively solves the security problem of access control and sharing dissemination on digital media, and it would apply to digital right management applications.

    Effect of surface errors on the average power pattern  of reflector antennas
    WANG Meng;DUAN Baoyan;WANG Wei
    J4. 2014, 41(6):  188-194.  doi:10.3969/j.issn.1001-2400.2014.06.031
    Abstract ( 677 )   PDF (610KB) ( 714 )   Save
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    The method for evaluating the average power pattern of reflector antennas is proposed when they are subjected to random errors and systematic errors. Firstly, the average expression for the random phase error of the aperture field is derived by analyzing the manufacturing errors of the single panel and misaligned errors of panel frames. Subsequently, the closed-form expression for the tapered illumination correlation function is derived by incorporating the axial defocus of the feed caused by systematic deformation. Then a novel mathematical model is developed to evaluate the average power pattern efficiently caused by the random error and systematic error. Finally, detailed parametric simulations are performed based on a reflector antenna with a 65m diameter to investigate the overall effect of the random error and systematic error on the performance, and reference advices are given finally.

    Image enhancement using the improved partial differential equation
    CUI Hua;ZHOU Tingjie;GUO Lu;YUAN Chao;SONG Huansheng
    J4. 2014, 41(6):  195-198.  doi:10.3969/j.issn.1001-2400.2014.06.032
    Abstract ( 763 )   PDF (2126KB) ( 483 )   Save
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    Excellent preprocessing is necessary for the crack extraction from pavement images. This paper adopts the Partial Differential Equation method to do that, and then improves the P-M diffusion coefficient and fuses it with coherence enhancing diffusion, thus forming the new PDE model. The new PDE model makes the improved P-M diffusion dominates the region without crack edges and coherence enhancing diffusion close to the crack edges, thereby realizing the crack image denoising and enhancing in a more effective way. Theoretical analysis and simulation results consistently show that the proposed model outperforms the classical P-M model in terms of pavement image denoising and enhancing. Furthermore, after the pavement images are preprocessed by the proposed PDE model, cracks are detected more accurately, demonstrating the superiority of the proposed preprocessing method.