Mar 2006, Volume 1 Issue 1

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  • XU Jian-hua, ZHANG Xue-gong, LI Yan-da
    Minimum squared error (MSE) algorithm is one of the classical pattern recognition and regression analysis methods, whose objective is to minimize the squared error summation between the output of linear function and the desired output. In this paper, the MSE algorithm is modified by using kernel functions satisfying the Mercer condition and regularization technique; and the nonlinear MSE algorithms based on kernels and regularization term, that is, the regularized kernel forms of MSE algorithm, are proposed. Their objective functions include the squared error summation between the output of nonlinear function based on kernels and the desired output and a proper regularization term. The regularization technique can handle ill-posed problems, reduce the solution space, and control the generalization. Three squared regularization terms are utilized in this paper. In accordance with the probabilistic interpretation of regularization terms, the difference among three regularization terms is given in detail. The synthetic and real data are used to analyze the algorithm performance.
  • ZHOU Ping
    The design of observers for a class of practical physical chaotic systems is discussed. By using only one state variable and its time derivatives, a control law is constructed to achieve the synchronization between the investigated chaotic systems and their observers, and the results are proved theoretically. Several observers of chaotic systems are designed by using this method.
  • JIANG Wan-lu
    The chaotic motion characteristics are expounded by taking the Duffing equation system as an example. The frequency band segmentation ability and the frequency resolution of the orthogonal multiresolution analysis and the orthogonal wavelet packet analysis are compared. A new orthogonal wavelet packet analysis-based chaos recognition method for chaotic motion characteristics is put forward. The chaotic, random, and periodic motions are identified effectively by use of the subfrequency band energy distribution in the signal spectrum. The characteristic frequency of chaotic motion is thus extracted.
  • YANG Qiong, DING Xiao-qing
    A novel face verification algorithm using competitive negative samples is proposed. In the algorithm, the tested face matches not only with the claimed client face but also with competitive negative samples, and all the matching scores are combined to make a final decision. Based on the algorithm, three schemes, including closestnegative-sample scheme, all-negative-sample scheme, and closest-few-negative-sample scheme, are designed. They are tested and compared with the traditional similaritybased verification approach on several databases with different features and classifiers. Experiments demonstrate that the three schemes reduce the verification error rate by 25.15%, 30.24%, and 30.97%, on average, respectively.
  • WANG Zuo-ying, XIAO Xi
    To overcome the defects of the duration modeling in the homogeneous Hidden Markov Model (HMM) for speech recognition, a duration-distribution-based HMM (DDBHMM) is proposed in this paper based on a formalized definition of a left-to-right inhomogeneous Markov model. It has been demonstrated that it can be identically defined by either the state duration or the state transition probability. The speaker-independent continuous speech recognition experiments show that by only modeling the state duration in DDBHMM, a significant improvement (17.8% error rate reduction) can be achieved compared with the classical HMM. The ideal properties of DDBHMM give promise to many aspects of speech modeling, such as the modeling of the state duration, speed variation, speech discontinuity, and interframe correlation.
  • ZHANG Ge-xiang, LI Na, JIN Wei-dong, HU Lai-zhao
    By introducing strong parallelism of quantum computing into evolutionary algorithm, a novel quantum genetic algorithm (NQGA) is proposed. In NQGA, a novel approach for updating the rotation angles of quantum logic gates and a strategy for enhancing search capability and avoiding premature convergence are adopted. Several typical complex continuous functions are chosen to test the performance of NQGA. Also, NQGA is applied in selecting the best feature subset from a large number of features in radar emitter signal recognition. The testing and experimental results of feature selection show that NQGA presents good search capability, rapid convergence, short computing time, and ability to avoid premature convergence effectively.
  • HU Fei, WEN Hong, CHEN Hua-wei
    Based on the generalized Chirp-like sequences, the product technique is extensively used to construct a new family of spreading sequences, and its correlation property is verified. The results show that among the proposed sequences, there are subclasses of sequences with a zero-correlation zone, which can be used in quasi-synchronous-code division multiple access systems.
  • WANG Bu-hong, WANG Yong-liang, CHEN Hui, GUO Ying
    The generalized maximum likelihood (GML) algorithm for direction-of-arrival estimation is proposed. Firstly, a new data model is established based on generalized steering vectors and generalized array manifold matrix. The GML algorithm is then formulated in detail. It is flexible in the sense that the arriving sources may be a mixture of multiclusters of coherent sources, the array geometry is unrestricted, and the number of sources resolved can be larger than the number of sensors. Secondly, the comparison between the GML algorithm and the conventional deterministic maximum likelihood (DML) algorithm is presented based on their respective geometrical interpretation. Subsequently, the estimation consistency of GML is proved, and the estimation variance of GML is derived. It is concluded that the performance of the GML algorithm coincides with that of the DML algorithm in the incoherent sources  case, while it improves greatly in the coherent source case. By using genetic algorithm, GML is realized, and the simulation results illustrate its improved performance compared with DML, especially in the case of multiclusters of coherent sources.
  • NI Wei, WANG Zong-xin
    The distance-loss  model is amended by inserting a random distance-estimation variable. The estimation error is very small; thus, it does not change the log-normal distribution of the shadowing factor in the model. Then, an iterative method is introduced to reduce the influence of shadowing, and the location estimation based on the received signal strength will be improved. Simulations show that this algorithm is effective.
  • JIANG Jun-feng, LIN Tie-gen, ZHANG Yi-mo, SUN Jie, DING Sheng, LI Chuan
    The Talbot interferometer used for writing fiber Bragg grating (FBG) is analyzed effectively in this paper. Based on electromagnetic theory, a computing model of the Talbot interferometer is established with the temporal and the spatial coherence taken into account and with the turning angle of the reflectors as a critical parameter. The model can provide a more detailed and precise information about the interference field and is used to study the effect of the turning error of the reflectors in writing FBG. The calculation result shows that the turning error has an important effect on the visibility of the far interference field.
  • BI Jian-guang, DONG Xin-zhou, GUO Yong-ji
    A new algorithm for fault superimposed quantity (FSIQ) is presented and analyzed. The network equations are built up by combining fault superimposed networks (FSIN) with the boundary conditions of FSIQ at the fault point and are solved with the Newton iterative method. The algorithm has clear physical meaning and does not require an intermediate procedure to derive FSIQ. The algorithm is implemented by computer programming, and the results of calculations show that the algorithm is fast and accurate. The method can be used not only to calculate FSIQ in the complex power systems with simple or multiple faults, but also to analyze and evaluate the performance of the protective relays and automatic devices based on FSIQ.
  • JIN Wan-bing, ZHANG Dong, AN Zhong-liang, TAN Ren-yuan
    On the basis of a conventional permanent magnet (PM) synchronous generator s construction, a novel kind of Hybrid Excitation Permanent Magnet Synchronous Generator (HEPMSG) is introduced by inserting exciting winding in the stator or rotor. Firstly, the construction of HEPMSG is improved with the addition of PM excitation on the ferromagnetic pole, and its working principle and design method are studied in detail. Then, an appropriate exciting current control system is presented considering the characteristics of HEPMSG. Finally, a prototype is made, and test results confirm the analysis and design.
  • LIU Rui-fang, YAN Deng-jun, HU Min-qiang
    When designing a universal finite element software for analyzing a permanent magnet synchronous motor, the relative position of the stator and rotor remains unknown. However, determining the relative position is a precondition for electromagnetic field calculation. Through analyzing the basic relationship of variables in a synchronous machine, the characteristics of an air-gap-resultant electromotive force and an inner power angle under a special inner power factor angle are obtained. A method similar to inverse problem solving is proposed. A series of electromagnetic field calculation under different armature current initial phase angles are carried out, and through searching the field of a special inner power factor angle, the relative position of the rotor and the stator can be determined subsequently.
  • YANG Ying
    Lead zirconium titanate (PZT) films (Zr/Ti=45:55) with a high dielectric constant are prepared successfully on the low-resistance Si substrate in sol gel dip-coating process with PT film used as the buffer layer. The dielectric and ferroelectric properties of the films as well as the relationship between crystallization and preparing condition are studied. It is shown that the PZT ferroelectric thin films with a (110) preferred orientation and a well-crystallized perovskite structure could be obtained after annealing at 800?C for 15 min. The particle size of the sample is about 14 25 nm. TheP E hysteresis loops are measured by means of the Sawyer Tower test system with a compensation resistor at room temperature. The remanent polarization (Pr) and coercive electric field (Ec) of the measured PZT thin films are 47.7 ?C/cm2 and 18 kV/cm, respectively. The relative dielectric constant Sr and the dissipation factor tg? of the PZT thin films were measured with an LCR meter and were found to be 158 and 0.04 0.005, respectively.
  • ZHANG Zhao-hua, YUE Rui-feng, LIU Li-tian
    A digital accelerometer is developed by using a ring oscillator (RO) and a mixer. The sensitive unit of the accelerometer is the metal-oxide semiconductor (MOS) ROs located on silicon beams. Based on the piezoresistive effect of the MOS RO, the accelerometer transduces the acceleration into frequency output. The syntonic frequency of the MOS RO changes in relation to many environmental elements, such as temperature, source voltage, and so on. The mixer is an interior signal processor that improves the output signal characteristics, with the digital output signal representing the frequency change. As the accelerometer is based on the piezoresistive effect of the MOS RO, the frequency characteristics of the MOS RO and its relationship with the acceleration are described. The device has been fabricated using standard integrated circuits processing methods combined with the Micro-Electro-Mechanical Systems process. The characteristics of the sample chip are in agreement with the theoretical predictions. The accelerometer has a high sensitivity of 6.91 kHz/g, a low temperature coefficient, and a simple fabrication process.
  • ZHONG Xue-fei, YIN Han-chun, WANG Bao-ping
    A carbon-nanotube-based normally-on-driving under-gate field emission display (FED) panel and its operation principle are presented. In this panel, field emission electrons are extracted directly from the cathode by the high anode voltage. The image is realized by modulating the voltage of under-gate, whose value is less than the cathode voltage, to stop the cathode producing field emission electrons. The electric field inside the emission region is calculated by the finite element method. The emission property of the cathode is also studied by numerical calculation method. The results indicate that a uniform and large emission area can be obtained in this new under-gate FED panel. This study provides powerful theoretic support for the feasibility of this new kind of under-gate FED panel.
  • HE Xiao-xiang, XU Jin-ping
    The Leontovich impedance boundary condition (IBC) is combined with the edge-based finite element method (FEM) in this paper to analyze the electromagnetic (EM) scattering of cavities coated with a multilayered dielectric. The IBC on the surface of the medium and the boundary integral equation on the aperture of the cavity are transformed into the third boundary condition, and then the functional of the boundary value problem is obtained. The surface impedance of the layered dielectric is calculated by the generalized reflection coefficient; hence, the multireflection of the EM wave in the dielectric is involved. As a result, the IBC is improved. Numerical results are presented, which demonstrate that the presented IBC/FEM approach is accurate and convenient for the analysis of EM scattering of open-ended cavities coated with the dielectric.
  • ZHOU Yu-fei, CHEN Jun-ning, KE Dao-ming, TSE Chi K., QIU Shui-sheng, SHI Long-xing, SUN Wei-feng
    In view of reasonable explanation of intermittent subharmonics and chaos that can be gained from coupling filter between circuits, this paper discusses a method that maps time bifurcation with parameter bifurcation. Based on this mapping method, the general analysis method of characteristic multiplier, which is originally aimed at parameter bifurcation, can be used for the study of intermittency, i.e., time bifurcation. In this paper, all researches coming from characteristic multipliers, parameter-bifurcation diagrams, and the largest Lyapunov exponent indicate the same results as those produced by simulation and experiment. Thus, it is proved theoretically that the intermittency in switching power converter can be explained in terms of coupling of spurious interference.
  • LU Zhen-su, HOU Zhi-rong, DU Juan
    A new adaptive mutation particle swarm optimizer, which is based on the variance of the population's fitness, is presented in this paper. During the running time, the mutation probability for the current best particle is determined by two factors: the variance of the population's fitness and the current optimal solution. The ability of particle swarm optimization (PSO) algorithm to break away from the local optimum is greatly improved by the mutation. The experimental results show that the new algorithm not only has great advantage of convergence property over genetic algorithm and PSO, but can also avoid the premature convergence problem effectively.
  • FAN Qi-fu, SHI Song-jiao
    One of the basic issues in the study of hybrid systems is the well-posedness (existence and uniqueness of solutions) problem of discontinuous dynamical systems. This paper addresses this problem for a class of piecewise affine discontinuous systems with affine inequalities such as systems with pulse-width modulator under the definition of Carath?odory solutions in terms of an analysis based on lexicographic inequalities and the smooth continuation property of solutions. Furthermore, it is clear that when carrier signalh (t)=0, closed-loop pulse-width modulation (PWM) DC DC converters are not well posed, and when some condition is satisfied, the closed-loop PWM DC DC converters with a P controller are well posed.
  • MA Hong-guang, HAN Chong-zhao
    A new algorithm is proposed for computing the embedding dimension and delay time in phase space reconstruction. It makes use of the zero of the nonbias multiple autocorrelation function of the chaotic time series to determine the time delay, which efficiently depresses the computing error caused by tracing arbitrarily the slop variation of average displacement (AD) in AD algorithm. Thereafter, by means of the iterative algorithm of multiple autocorrelation and Γ test, the near-optimum parameters of embedding dimension and delay time are estimated. This algorithm is provided with a sound theoretic basis, and its computing complexity is relatively lower and not strongly dependent on the data length. The simulated experimental results indicate that the relative error of the correlation dimension of standard chaotic time series is decreased from 4.4% when using conventional algorithm to 1.06% when using this algorithm. The accuracy of invariants in phase space reconstruction is greatly improved.
  • LUO Da-yong, ZHANG Yuan
    To receive habitus accurately and to obtain the reorganization and decision information of the object fully, spatial and temporal fusion must be taken into account. In this paper, a spatial temporal two-layer architecture model is presented. In this architecture, the data monitored by different sensors at the same time are fused first in space, and then in time order. Based on this model, we give an algorithm based on the theory of D S evidence and fuzzy integral for sensor fusion. Simulation results indicate that this algorithm can improve the efficiency of object identification and the reliability of system. The simulation of the algorithm in multisensor object identification is also presented.
  • LIN Jia-ru, WU Wei-ling
    This paper analyzes and simulates the performance of irregular low-density parity check (LDPC) codes on Rician fading channels. The authors also modified the brief propagation decoding algorithm, proved the symmetry and showed the stability conditions of the channels, and calculated the Shannon limits on Rician channels in this paper. By using Visual C++ programming to simulate the performance, the result indicates that when code length N = 3,072 and code rate R = 1/3, the difference with the Shannon limit is about 2 dB. Therefore, the performance of LDPC is also very effective on all kinds of channels, including the Rician kind.