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    20 October 2008 Volume 35 Issue 5
      
    Original Articles
    New method for suppression of the clutter of the wideband target recognition radar
    HOU Qing-yu;LIU Hong-wei;BAO Zheng
    J4. 2008, 35(5):  769-773. 
    Abstract ( 2137 )   PDF (790KB) ( 1375 )   Save
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    Traditional clutter suppression is inapplicable to the wideband radar due to the migration through resolution cells during coherent echoes. In this paper, a new method for clutter suppression in the frequence-doppler domain is proposed for the wideband radar. If the target velocity is acquired, it can be utilized to perform the velocity compensation and then the extraction of target information; without the target velocity, the improved Hough transform algorithm is proposed to extract target information, which is equivalent to accomplishing clutter suppression.Meanwhile, the proposed method is able to avoid the loss of target information during clutter suppression. Experimental results on simulated data demonstrate that our approach can provide a satisfying recognition performance, even though the input SCR is -10dB(with the velocity unknown) or -15dB (with the velocity known). Furthermore, the algorithms are still robust to the noise even at -5dB SNR.
    Locally knowledge-based InSAR baseline estimation method
    SUO Zhi-yong;LI Zhen-fang;WU Jian-xin;BAO Zheng
    J4. 2008, 35(5):  774-776. 
    Abstract ( 1667 )   PDF (503KB) ( 897 )   Save
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    The accuracy of InSAR baseline measurement or estimation is the key factor of digital elevation model (DEM) generation. In this paper, a locally knowledge-based InSAR baseline estimation method is proposed, which estimates the InSAR baseline using the interferogram with the flattened earth removal. Choosing two points with the same height after unwrapping the interferogram, and according to the relationship between the baseline and the target point height without knowing the absolute InSAR phase value or the relative difference of the two points, the method can estimate baseline parameters without knowing ground control points. Its validity is illustrated through computer simulations and the estimation accuracy can be achieved at the level of centimeters.
    Blind along-track baseline estimation using radar echoes
    YANG Zhi-wei;LIAO Gui-sheng;ZENG Cao
    J4. 2008, 35(5):  777-780. 
    Abstract ( 1862 )   PDF (572KB) ( 955 )   Save
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    For the purpose of estimation of the along-track baseline in the absence of an auxiliary calibrating source, a new algorithm which is performed in two stages is proposed. The first stage is carried out at Doppler beam sharpening (DBS) images to estimate channel phase relationship by eigen-decomposing of the phase correlation matrix. Thus the problem of target signal contamination can be alleviated observably. Finally, the along-track baseline is estimated based on the unwrap phase of the clutter space steering vector by using the least square algorithm. The effectiveness for along-track baseline mismatch and the robustness for target signal contamination are confirmed by performance analysis and extensive simulation.
    Estimation of the moving angle and velocity of the target in the MIMO radar
    QU Yi1;2;LIAO Gui-sheng1;ZHU Sheng-qi1;LI Jun1
    J4. 2008, 35(5):  781-784. 
    Abstract ( 1786 )   PDF (546KB) ( 1006 )   Save
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    Based on the MIMO model which has multiple spatially separated transmitters and co-located separated receivers, the moving angle and velocity are estimated by the relation between velocity vectors of a target for all transmitter-receiver pairs. Based on this estimation, the radial velocity toward the receiver is obtained by projecting the moving velocity vector onto the looking direction from receiver to target and its performance formula is achieved. Theoretical analysis and simulation results show that velocity estimation for the MIMO radar is related to the angle between the vectors from the target to the receiver and transmitters, and the greater this angle, the smaller the estimation error.
    Multiple targets angle tracking algorithm based on the elements of the covariance matrix

    ZHANG Huai-gen;WU Shun-jun;ZHANG Lin-rang;LIU Yin
    J4. 2008, 35(5):  785-792. 
    Abstract ( 1902 )   PDF (893KB) ( 1260 )   Save
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    Based on the elements of the covariance matrix, this paper presents a multiple targets angle tracking algorithm, in which by updating the elements of the covariance matrix, a set of linear equations is derived through linear approximations. Angle difference can be obtained by solving these equations. Different from the subspace tracking algorithm, this method need not update the signal subspace; the angles estimated at different times are auto associated, so we can omit the process of data association. This method works well when the number of targets is greater than the number of sensors. At the same time, this algorithm can diminish the effect of noise. Simulation results show this algorithm has high tracking performance.

    New method for DOA estimation for the MIMO radar in low-angle tracking environment

    WU Xiang-dong;ZHAO Yong-bo;ZHANG Shou-hong;DONG Mei
    J4. 2008, 35(5):  793-798. 
    Abstract ( 2064 )   PDF (610KB) ( 950 )   Save
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    This paper proposes a new DOA (direction-of-arrival) estimation in low-angle tracking environment. For the MIMO radar, not only received multipath signals but also transmitted multipath signals should be considered due to the multipath effect. The proposed algorithm applies a double port signal processing to receivers and transmitters based on the improved Maximum Likelihood method which only needs one dimension search on space. This process can extend the array aperture respect to the case of single port array signal processing. Hence the new algorithm improves the resolution and accuracy of DOA estimation of the elevation at a low SNR and has low computational complexity.
    Appearance model based on blobs for object tracking
    WANG Shu-peng1;2;JI Hong-bing1
    J4. 2008, 35(5):  799-804. 
    Abstract ( 2187 )   PDF (1424KB) ( 1382 )   Save
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    This paper proposes a novel local feature-based object tracking algorithm. The object is segmented into a few regions using multiple scale segmentation, and each region is denoted as a blob which combines the local color, shape and location. An object appearance model is built based on the blob feature. The object is tracked by the blob matching criterion defined. The appearance model includes the local color and spatial structures, so the object can be tracked in the condition of partial occlusion and change of the object scale. Examples demonstrate that the proposed algorithm can obtain the accurate tracking results in the complex environment and has better performance than the well-known mean shift algorithm.
    Non-cooperative game theoretical admission control algorithm for traffic flows in wireless LANs
    ZHANG Guo-peng;ZHANG Hai-lin
    J4. 2008, 35(5):  805-810. 
    Abstract ( 1959 )   PDF (714KB) ( 1187 )   Save
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    An admission control (AC) algorithm based on the non-cooperative game theory is presented for IEEE 802.11 WLANs. By setting the user QoS satisfaction ratio (UQS) function, the AC procedure between the wireless users and the Access Points (APs) is modeled as a non-cooperative game where the users and the ACs want to maximize their UQS function based utilities. According to the Nash equilibria of the game, an adaptive AC alogrithm called the G-AC is then developed. Simulation results indicate that the QoS of the ongoing user flows is guaranteed by the G-AC algorithm. And since the G-AC algorithm can adjust the admission strategy in accord with the current system load, it has notable advantages over other AC algorithms in both bandwidth utilization and network revenue.
    Diversity algorithm for the small-space array antenna for MIMO-OFDM systems
    LI Wen-gang;YI KE-chu;WANG Ying-min;SONG Wei
    J4. 2008, 35(5):  811-815. 
    Abstract ( 1926 )   PDF (598KB) ( 1182 )   Save
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    For the small-space array antenna, the spatial channels exhibit high correlation. Under this scenario, the space-frequency block codes(SFBC) scheme cannot lead to significant diversity gains. This paper proposes a new diversity method-SDA(small space array atenna diversity algorithm), which can lead to a great diversity gain without any channel state information (CSI) in the transmitter. By scheduling the symbols in the frequency domain, we have improved the error performance of small-space array antenna MIMO systems. The results of LTE downlink simulation shows that the error probability will be reduced form 0.1 to 0.01 when the signal noise rate(SNR) is 6dB and the code rate is 2／3.
    Movement control algorithms for realizing the balance of transmission power for sensor networks
    GONG Wei-bin;SHEN Zhong;CHANG Yi-lin
    J4. 2008, 35(5):  816-822. 
    Abstract ( 1720 )   PDF (1127KB) ( 1070 )   Save
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    In wireless sensor networks, in order to prolong network life time and improve network capacity, it is necessary to introduce a new technique to reduce the difference of transmission power, which can not be solved by traditional topology control algorithms. Two movement control algorithms, PMST-P and PMST-UV, are proposed in this paper. With the network connectivity unchanged, a topology with the distribution of transmission power being more uniform can be constructed by determining additional links and moving nodes based on the network partition graph and letting moving nodes move to positions of additional links. Simulation results show that both the algorithms can reduce the maximum communication radius to below the critical communication radius and thus can improve the performance of topology control dramatically. Moreover, the PMST-UV algorithm outperforms the PMST-P algorithm, with the moving distance of the former only 50％ that of the latter and the ratio of moved nodes being 0.4 less.
    Chromatic dispersion performance analysis of ODPASK modulation format in optical communication
    LI Xiao-jun1;2;WEN Ai-jun1;LIU Zeng-ji1;SHANG Tao1;ZHAI Wan-teng1
    J4. 2008, 35(5):  823-829. 
    Abstract ( 1743 )   PDF (2232KB) ( 939 )   Save
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    The chromatic dispersion performance of the 120Gbit／s ODPASK modulation format is investigated in the single channel system. The optimal back-to-back extinction ratio is derived, so that the equivalent eye opening is obtained for the amplitude tributary and phase tributary. Then the influence of the different duty cycles on the chromatic dispersion tolerance of the two tributaries is studied. Simulation results show that the amplitude tributary mainly degrades the chromatic dispersion performance of the ODPASK transmission system, and that eye-opening penalties of the two tributaries vary inversely with the increasing duty cycle.
    Analysis of the effect of polarization mode dispersion on QKD
    HAN Bao-bin;PEI Chang-xing;CHEN Nan;YI Yun-hui
    J4. 2008, 35(5):  830-833. 
    Abstract ( 1990 )   PDF (596KB) ( 1009 )   Save
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    Affected by PMD(Polarization Mode Dispersion), the polarization state of the single photon will be randomly and slowly altered during the transmission in the fiber. This increases the error probability at the receiving end. So a means for measuring the variance to the preprocess polarization state is required for the distribution of the quantum key. A sensor with balanced detection is introduced to the BB84 protocol and the theoretical model of the QBER (Quantum Bit Error Rate) is established with POVM (Positive Operator Valued Measurement). The variance of the polarization state is measured with the Wollaston prism and the error is eliminated for the dual channel. The angle tolerance of the Wollaston prism is 0.1° and the numerical analysis by the use of the QBER model shows the new protocol decreases the error rate to 3.05×10<sup>-6</sup>.
    Encoding and decoding of a family of quantum stabilizer codes
    LI Zhuo;XING Li-juan;WANG Xin-mei
    J4. 2008, 35(5):  834-837. 
    Abstract ( 1570 )   PDF (547KB) ( 944 )   Save
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    A family of special quantum stabilizer codes is defined with the property that in the stabilizer all phases are 1 and the part of bit-flip is cyclic, which includes well-known CSS codes. Its encoding and decoding are present. The encoding process needs an encoded 0 state to begin with. Then any encoded state can be obtained by control of the logical state. Decoding could be performed by running the encoding process backwards with the output of the encoded 0 state besides the desired logical state. This encoded 0 state can be used in the next encoding directly, which simplifies encoding and decoding greatly because the complexity of this method lies in producing the encoded 0 state. These processes possess a highly regular structure.
    Low-distortion high-bandwidth analog switch applied to high-speed signal transmission
    CAO Han-mei1;CAI Wei2;YANG Yin-tang1;LU Tie-jun2;WANG Zong-min2
    J4. 2008, 35(5):  838-841. 
    Abstract ( 1801 )   PDF (666KB) ( 1273 )   Save
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    A low-distortion high-bandwidth bootstrap analog switch suitable for high-speed signal transmission is presented. The gate-to-source voltage of the switch is set by the combined on-voltage of a PMOS and an NMOS, and the difference between the gate-source voltage and the threshold voltage (V<sub>GST</sub>) of the switch is constant with a rail-to-rail input, with the body effect also nearly canceled. Implemented in the TSMC 0.18μm CMOS process, results from HSPICE simulation show that the V<sub>GST</sub> is nearly constant with the input ranging from 0 to 1.8V, and that the -3dB bandwidth is larger than 10GHz. When the input frequency is 1.5GHz, and full-scale range is 0.8V, the output can follow the input nearly without attenuation, and its SFDR(spurious free dynamic range) is 65.4dB.
    Accurate calculation of the specific contact resistance for Ni based Ohmic Contacts to the N-type SiC
    GUO Hui;ZHANG Yi-men;ZHANG Yu-ming;TANG Xiao-yan;FENG Qian
    J4. 2008, 35(5):  842-845. 
    Abstract ( 2125 )   PDF (539KB) ( 1030 )   Save
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    The specific contact resistance of ohmic contact is deduced accurately based on the electron tunneling probabilities through the triangular barrier to be solved by the one-dimensional time-independent Schrdinger equation. The experimental results of Ni based ohmic contacts on the N-type SiC are compared with that of the simulation. The proposed method has the advantages over the WKB approximation of better accuracy and adaptation to SiC ohmic contacts.
    SAR image segmentation using optimized FCM with weighted spatial function
    TIAN Xiao-lin;JIAO Li-cheng;GOU Shui-ping
    J4. 2008, 35(5):  846-852. 
    Abstract ( 2261 )   PDF (2005KB) ( 1122 )   Save
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    Because the spatial information is not considered in the traditional fuzzy c-means (FCM) clustering algorithm, the serious inaccuracies with synthetic aperture radar (SAR) image segmentation can be caused by using the FCM algorithm. To improve the SAR image segmentation result, the weighted spatial membership and weighted spatial function are introduced into the FCM algorithm in this paper. The weighted spatial membership is composed of the weighted membership of the relative location and intensity of neighboring pixels under the condition of the multi-scale space. The influence degrees of the weighted spatial membership on the weighted spatial function are optimized by the adaptive genetic algorithm (AGA). The final membership of each pixel is adjusted by the weighted spatial function. Due to the introduction of the optimized spatial information during the process of clustering, the influence of the speckle in SAR images is minimized and the classification accuracy is improved. In our experiments, the real SAR images are segmented and the segmentation results demonstrate the superiority of the proposed algorithm to other methods. This algorithm is not sensitive to the initial segmentation result and is robust to despeckling.
    Parallel immune clonal selection for feature selection

    ZHU Hu-ming;JIAO Li-cheng
    J4. 2008, 35(5):  853-857. 
    Abstract ( 2226 )   PDF (594KB) ( 1222 )   Save
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    Focusing on the time-consuming problem of wrapper feature selection when the feature subset is evaluated using high-complexity classifiers in pattern recognition, a novel parallel immune clonal selection for feature selection algorithm (PICFS) is proposed. The presented method uses an immune clonal selection for feature selection; fitness of feature subset fitness is determined by evaluating the nearest neighbor classifier with leave-one-out cross-validation in multiple computing nodes at the same time. Experimental results on several standards UCI dataset sets show that the proposed algorithm outperforms the conventional genetic algorithm and classical sequential floating forward search algorithm in terms of classification accuracy and greatly reduce the running time based on MPICH using the Linux blade cluster, we have achieved a speed-up as high as 29.57 even when up to 40 processors are used.
    Approach to SAR ground moving target indication and localization based on the joint eigen steering vector for the multi-channel SAR system
    ZHOU Zheng-guang;LIAO Gui-sheng
    J4. 2008, 35(5):  858-863. 
    Abstract ( 2000 )   PDF (807KB) ( 1075 )   Save
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    A robust approach to ground moving target indication and localization is proposed for the multi-channel SAR system in the presence of coregistration errors. In the proposed approach， the joint eigen steering vector of a moving target is constructed according to its space steering vector and eigen coefficient vector, the optimal beamforming approach is used to suppress the clutter, the velocity of the moving target can be determined simultaneously, and the moving target can be relocalized subsequently. This method has good robustness to image coregistration errors, and can provide accurate estimate of the ground moving target radial velocity. The validity and superiority of this method are verified by simulated data.
    Joint eigenbeam and space-time coding over the frequency-selective fading channel for diversity
    WANG Yong;LIAO Gui-sheng;WANG Xi-yuan
    J4. 2008, 35(5):  864-870. 
    Abstract ( 1805 )   PDF (694KB) ( 973 )   Save
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    A Space-Time Eigenbeam Coded scheme is discussed to improve the performance of Space-Time Coding for downlink wideband correlated fading channels. This novel transmission scheme combining Eigenbeam forming with OFDM is proposed. A group of eigenvectors of the Spatial-Correlated-Matrix (SCM) is introduced as the weights of the Space-Time code-matrix. The scheme can channel the transmit power in the directions with the biggest gains and convert correlated fading channels into an independent FIR channel with 2 transmitting antennas and N receiving antennas by Eigenbeam forming and reducing the dimensions. Then OFDM is utilized to convert this FIR channel into a group of independently paralIe1 subchannels to carry Space-Time Codes. The BER(Bit Error Rate) performance comparisons with the traditional Alamouti code under different multi-path and transmit antenna conditions, through extensive Monte-Carlo simulation. The simulation results show that the proposed scheme has a lower BER than the traditional Alamouti code and the Signal-to-Noise Rate (SNR) is higher meanwhile. The performance is 5dB higher than that of the traditional Alamouti code under 6 transmitting antennas and 16 paths. The proposed scheme leads to a better diversity gain and increases equivalent channel total power.
    New method for microcalcification clusteres detection using active learning in the mammogram
    ZHANG Xin-sheng1;2;GAO Xin-bo1;WANG Ying1;ZHAO Wen-qi1
    J4. 2008, 35(5):  871-877. 
    Abstract ( 2250 )   PDF (1169KB) ( 1035 )   Save
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    A new approach to microcalcification clusters detection is proposed, based on active learning. The proposed algorithm first enhances the microcalcification region with a directional difference filter bank which effectively realizes the feature extraction and meanwhile suppresses the blood vessels and mammary duts. Then the active sample selecting method based on Bootstrap is employed to select the training set and train the Baysian classifier. Finally the obtained classifier can be used to detect microcalcification clusters in the mammogram. Experimental results show that the proposed algorithm achieves good performance. Compared with the traditional passive learning methods, the new algorithm reduce the false positive rate 4.7％ by keeping the same sensitivity.
    Color gamut mapping algorithm based on vision evaluation model
    WANG Yi-feng;LUO Xue-mei;ZENG Ping
    J4. 2008, 35(5):  878-882. 
    Abstract ( 1653 )   PDF (1155KB) ( 1300 )   Save
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    To solve gamut mismatch problems in color reproduction across different devices, a new color gamut mapping algorithm is proposed. First, by analyzing the subjective assessment process, a gamut mapping evaluation model via human vision system is defined, and their consistence is proved. Then under the guidance of the model and by considering both image colors and image spatial characteristics, a divide and conquer scheme is employed and a mapping fusion model is constructed to implement the method. Experiments show that the proposed algorithm has obvious advantage over traditional ones, especially in color difference and image details.
    3D image reconstruction using the InISAR technique
    GAO Zhao-zhao;XING Meng-dao;ZHANG Shou-hong
    J4. 2008, 35(5):  883-888. 
    Abstract ( 1926 )   PDF (868KB) ( 1037 )   Save
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    The model of the interferometric inverse synthetic aperture radar (InISAR) three-dimensional imaging is proposed when the angle between the target and the antenna axis is relatively large. The measurement error induced by the motion compensation error is discussed in detail and the motion compensation scheme is presented. Because the phase difference is 2π-periodic, the influence of the motion compensation error on the mearsurement result is also periodic, which may cause the ambiguity of the image in the cross-range. In this method, the phase of the image’s barycentre is estimated, and then the barycentre is used as a reference for compensating the phase diferrence for the correction of the target’s cross-range shift. The scatterers’ height and width measured are not the correct coordinates of the target because they are not obtained in rectangular coordinates. The formula for transforming the measured coordinates into rectangular coordinates and generating a correct 3D image is given. Finally, the simulation results are given.
    Novel center-fed cage antenna using the composite structure
    LI Jian-feng;SUN Bao-hua;LIU Qi-zhong;ZHOU Hai-jin
    J4. 2008, 35(5):  889-893. 
    Abstract ( 1912 )   PDF (848KB) ( 2215 )   Save
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    A novel center-fed cage antenna using the composite structure is proposed. The antenna has a composite structure of a cage and an asymmetric biconical structure. The impedance bandwidth and radiation pattern bandwidth are enhanced, and the tilting and ripping of radiation patterns are eliminated. A helical shorting wire is used to reduce the antenna height effectively. The antenna is analyzed and optimized by the method of moments (MOM). A prototype operating in VHF／UHF bands is constructed and tested. Measured results show that a VSWR (less than 3.0∶1) bandwidth of 650 MHz(100～750MHz), without additional matching or loading network, is obtained. The overall measured radiation gain of the proposed antenna in the horizontal plane is stable and larger than 1.5dBi in the operating frequency band(100～400MHz). Furthermore, a size reduction rate of 50％ compared with a general dipole antenna is realized.
    General analysis method of rectangular waveguide discontinuities by mode matching
    ZHAO Wei1;ZHAO Yong-jiu1;LU Hong-min2
    J4. 2008, 35(5):  894-898. 
    Abstract ( 1586 )   PDF (598KB) ( 1058 )   Save
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    In rectangular waveguide discontinuity analysis by mode matching, the traditional method infers a different expression according to a different discontinuity. The program creates a serious inconvenience, so there need be a unified approach to analyzing the rectangular step. This paper infers the unified generalized s-parameter matrix formula of the step in the thick diaphragm and in the E-plane septum by mode matching. Finally, two rectangular band pass filter examples are included. The curve results agree well and the calculation time is greatly shortened compared with the HFSS, which verifies the validity of this technique.
    Method for obtaining a second signal based on the phase coincidence sign between two frequency signals
    QU Ba-yi;ZHOU Wei;QIN Hong-bo;LI Zhi-qi
    J4. 2008, 35(5):  899-902. 
    Abstract ( 1545 )   PDF (544KB) ( 963 )   Save
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    The method for generating the second signal is put forward based on the period rule of the phase difference for two frequency signals with the frequency difference. The two frequency signals with a certain frequency difference can be obtained from the same source. The phase coincidence detection circuit outputs an exclusive coincidence signal with the help of a time gate, and then the phases of the two frequency signals would be moved properly to make the coincidence signal synchronize to a normal second signal. Experiment shows that the method is same as the conventional one in generating a second signal, but facilitates the advantage of delivery and measurement of frequency signal when it is used in the time promulgation system. When used in the atomic clocks time comparison, the comparison can be fulfilled using the phase comparison of the frequency sources, so as to improve the accuracy as well as reduce the cost.
    Investigation on the electromagnetic scattering from the spheroid covered with the plasma
    WANG Rui;GUO Li-xin;YANG Ge
    J4. 2008, 35(5):  903-909. 
    Abstract ( 1456 )   PDF (788KB) ( 1109 )   Save
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    A solution to the electromagnetic scattering problem for core-mantle (two-layered) spheroidal particles is obtained by separation of variables in the spheroidal coordinate system by considering the boundary condition for the dielectric medium and the target. The incident field, the scattered field and the internal radiation field are divided into the axisymmetric and the non-axisymmetric part in this study. The angular distributions of RCS of the backscattering and bistatic scattering from the spheroid covered with the plasma are presented by numerical implementations, and the dependences of RCS on different physical quantities such as the incident frequency, the azimuth angle, the collision frequency, the electron concentration as well as the thickness of the plasma mantle are discussed in detail. The results obtained are of the important significance for the investigation of the core-mantle spheroidal particles covered with the plasma.
    Abnormal time synchronization data filter algorithm in sensor networks
    SUN Ji-min1;3;SHEN Yu-long2;PEI Qing-qi2;MA Jian-feng2
    J4. 2008, 35(5):  910-915. 
    Abstract ( 2547 )   PDF (626KB) ( 1182 )   Save
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    The time synchronization data filter estimative region is designed and a data filter algorithm based on linear regress is presented by using the distribution feature of the time bias and the linear feature of the time synchronization of node and the theory and the method of sample space estimation in probability statistics. This algorithm uses the estimative region to filter abnormal data and solves the problem that sensor networks are so easily attacked that the time synchronization is affected due to the high error rates of sensor networks. The algorithm is simple in decision process. The algorithm is avoided on the abnormal data. The computation costs are greatly reduced. The simulation result shows that this algorithm eliminates effectively the effect of the abnormal data on the estimated values of linear regress and increases the time synchronization accuracy.
    Effect of axial heat conduction and thermal entrance on heat transfer for the circular microchannel
    LIU Huan-ling;JIA Jian-yuan;YIN Lei
    J4. 2008, 35(5):  916-921. 
    Abstract ( 1597 )   PDF (571KB) ( 953 )   Save
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    A method for resolving the energy equation of the circular microchannel, which considers axial heat conduction, temperature jump, velocity slip and thermal entrance is presented. The energy equation can be transformed into the eigenvalue problem by separation of variables. The temperature jump condition provides a procedure for determining the eigenvalues. The undermined coefficients of the complete solution to the energy equation are derived by the orthogonality eigenfunction and then the expressions of temperature field and Nusselt number are obtained. The expressions for temperature and the Nusselt number are achieved. Simulation of heat transfer in the circular microchannel is conducted and it is revealed that heat transfer to the wall increases with the effect of axial conduction. The effect of thermal entrance is to increase the local Nusselt number. The smaller the velocity slip coefficient, the larger the asymptotic value of the Nusselt number.
    Adaptive fuzzy control for unknown nonlinear time-delay systems
    GUO Tao;ZHANG Jun-ying
    J4. 2008, 35(5):  922-926. 
    Abstract ( 1701 )   PDF (528KB) ( 920 )   Save
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    An adaptive fuzzy control design approach is proposed for a class of nonlinear time-delay systems that include unknown functions. Based on the backstepping design technique, unknown functions are approximated by fuzzy logic systems (FLS), and the adaptive bounding technique is employed to estimate the upper bound of the approximation errors. The appropriate Lyapunov-Krasovskii functional, combining with the domination technique, is constructed to compensate for the time delays. The closed-loop systems are proven to be semi-globally uniformly ultimately bounded, and the arbitrary output tracking accuracy is guaranteed by tuning the design parameters. Simulation result is presented to show the effectiveness of the approach.
    Reduced support vector domain description method RSVDD
    LIANG Jin-jin1;LIU San-yang1;WU De2
    J4. 2008, 35(5):  927-931. 
    Abstract ( 1574 )   PDF (547KB) ( 1026 )   Save
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    To accelerate the training of SVDD, a support vector domain description method RSVDD based on reduced sets is proposed. Since the boundary is determined by a small portion of data called support vectors which distribute around the description boundary; the proposed algorithm treats the distance to the center as a probability measure of support vectors for each sample, and selects the former ones ranking as the reduced sets to participate in the SVDD training. Simulations over artificial and benchmark data show its effectiveness and superiority: RSVDD reduces the training scale and the training time, while maintaining the accuracy of targets and outliers.
    Modulation recognition of MQAM signals in the passband
    CHU Yan-jie;HU Nian-fu;CHAO Kai-jin;PENG Xiao-cheng
    J4. 2008, 35(5):  932-937. 
    Abstract ( 1844 )   PDF (685KB) ( 983 )   Save
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    A modulation recognition algorithm for MQAM signals in the passband is presented. The proposed algorithm extracts the instantaneous envelope of the signals based on the Hilbert transform, and then the distribution vectors of the instantaneous energy are extracted. The algorithm extracting characters in the passband avoids the carrier frequency offset and the phase offset brought about by spectra shifting. The modulation recognition results of a few kinds of MQAM signals are given. The results show that the correct recognition probability of the algorithm is 100％ for 4QAM,8QAM,16QAM, it is above 95％ for 32QAM,128QAM, and above 90％ for 64QAM and 256QAM. The computer simulation verifies the validity of the algorithm.
    Algorithm for constructing QC_LDPC codes based on the weighted map

    HU Jia-yi;WANG Wen-bo
    J4. 2008, 35(5):  938-941. 
    Abstract ( 1713 )   PDF (521KB) ( 998 )   Save
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    A low complexity algorithm for constructing Quasi_cyclic low-density parity-check (QC_LDPC) codes with a large girth is presented. Based on the weighted graph, the algorithm leads to sets of values of all undetermined positions of the base matrix ensuring QC_LDPC with a large girth. The sets of values are determined without trying every possible value so that the complexity for constructing QC_LDPC codes is greatly reduced. Simulations show the algorithm can construct codes with a large girth which have good performances.
    Effective TDOA／AOA data fusion location algorithm for mitigating the influence of the NLOS propagation
    MAO Yong-yi1;LI Ming-yuan2;ZHANG Bao-jun1
    J4. 2008, 35(5):  942-945. 
    Abstract ( 1932 )   PDF (667KB) ( 980 )   Save
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    A time difference of arrival／angle of arrival (TDOA／AOA) data fusion location algorithm is proposed. The RBF neural network is made use of to correct the measurement of TDOA to mitigate the effect of the non-line-of-sight (NLOS) propagation, then the position of MS is calculated by the TDOA location algorithm and AOA location algorithm, and finally the position of MS is determined by the weighted average of TDOA and AOA location results. Simulation results indicate that this algorithm can significantly improve the location accuracy and reliability under suburban, urban and bad urban environments.
    Polyline data compression using total least squares
    YANG Yun1;2;SUN Qun1;ZHU Chang-qing3
    J4. 2008, 35(5):  946-950. 
    Abstract ( 1910 )   PDF (628KB) ( 1533 )   Save
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    In the well-known Ramer-Douglas-Peucker (RDP) algorithm for polyline data compression, only the points with distance greater than a given tolerance from polyline (a chain of vertices) to segment (the first and last vertices of the polyline) are retained, while all other points on the original polyline are deleted. This gives rise to inconsistent data compression accuracy among the retained and the deleted points. In this paper, a new algorithm based on total least squares is presented, which takes each subset of a polyline as a processing unit and uses all the points on the original polyline to fit a new line. These fitted lines are intersected to form a final polyline, thus leading to improved compression accuracy. An experiment is included, which shows that compared with the traditional RDP algorithm, the proposed method has smaller approximation errors, especially for larger tolerance.
    H∞ control of discrete-time descriptor systems with Markov jumping parameters
    TANG Zhong-yi;LIU Fei
    J4. 2008, 35(5):  951-956. 
    Abstract ( 1534 )   PDF (523KB) ( 929 )   Save
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    In order to solve the H∞ control problem for a class of discrete singular systems with markov parameters, a design method based on the memoryless state feedback controller of mode-jumping is proposed. By transforming the solvability of the determinant equation into the relationgship between the eigenvalue of the matrix and zero, the problem of regularity is converted to the magnitude of the maximum eigenvalue, and the causality is guaranteed in terms of linear transformation and the block matrix. By using the constructed Lyapunov function and linear matrix inequalities, a sufficient condition that the systems be admissible is given and proved, and a sub-optimal design approach is presented. The controller is designed and the prescribed H∞ performance condition is satisfied. Simulation results demonstrate that the proposed method is valid and that the system has strong restraint ability against disturbance.
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