Dec 2007, Volume 2 Issue 4

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  • ZHONG Yixin
    Advanced intelligence will feature the intelligence research in next 50 years. An understanding of the concept of advanced intelligence as well as its importance will be provided first, and detailed analysis on an approach, the mechanism approach, suitable to the advanced intelligence research will then be followed. And the mutual relationship among mechanism approach, traditional approaches existed in artificial intelligence research, and the cognitive informatics will be discussed. It is interesting to discover that mechanism approach is a good one to the Advanced Intelligence research and a unified form of the existed approaches to artificial intelligence.
  • CHEN Wei, CAO Zhigang, FAN Pingyi, Khaled B. Letaief
    In multi-user wireless communication systems, dynamic power allocation is an important means to deal with the time-varying nature of the physical and network layers. However, the current layer optimization approach to power allocation cannot achieve the global optimum of the overall system performance. To solve this problem, a cross-layer optimization framework is presented for downlink power allocation, which takes both the channel and buffer states into account. A cross-layer optimization problem is formulated to optimize the total throughput with queue length and power constraints. An analytical solution and a low complexity dynamic programming algorithm, which are referred as water-filling in cellar (WFIC) policy, are presented to optimize the downlink power allocation. Finally, simulation results are presented to demonstrate the potential of the proposed method.
  • ZHANG Jie
    In the research on spatial hearing and realization of virtual auditory space, it is important to effectively model the head-related transfer functions (HRTFs) or head-related impulse responses (HRIRs). In our study, we managed to carry out adaptive non-linear approximation in the field of wavelet transformation. The results show that the HRIRs  adaptive non-linear approximation model is a more effective data reduction model, is faster, and is 5 dB on average better than the traditional principal component analysis (PCA) (Karhunen-Lo?ve transform) model based on relative mean square error (MSE) criterion. Furthermore, we also discussed the best bases  choice for the time-frequency representation of HRIRs, and the results show that local cosine bases are more propitious to HRIRs  adaptive approximation than wavelet and wavelet packet base. However, the improved effect of local cosine bases is not distinct. Here, for the sake of modeling the HRIRs more truthfully, we consider choosing optimal time-frequency atoms from redundant dictionary to decompose this kind of signals of HRIRs and achieve better results than all the previous models.
  • YU Zheng, YANG Xing, ZOU Yongzhong, LI Daoben, SUN Yuhao
    A new class of loosely synchronous (LS) spreading sequences with zero correlation window (ZCW) was presented. It was constructed by making Kronecker product of orthogonal matrix and ZCW complementary sequences. This new LS sequence increases the number of perfect complementary pairs and extends ZCW within the same group. Moreover, both auto-correlation and cross-correlation of ZCW in the same group remain identical. The minimum ZCW among different groups is the same as that of basic LS sequences. The method for constructing these new LS sequences is presented and ZCW properties are also verified. The number of these new LS sequences is only smaller than theoretical upper bound by one.
  • LI Min, FENG Xiangchu
    This paper proposes a new model for the image restoration which combines the total variation minimization with the pure  anisotropic diffusion equation of Alvarez and Morel. According to the introduction of new diffusion term, this model can not only remove noise but also enhance edges and keep their locality. And it can also keep textures and large-scale fine features that are not characterized by edges. Due to these favorable characteristics, the processed images turn much clearer and smoother, meanwhile, their significant details are kept, which results in appealing vision.
  • YAN Songhua, WU Shicai, WEN Biyang
    The Doppler spectral broadening resulted from non-stationary movement of target and radio-frequency interference will decrease the veracity of target detection by high frequency ground wave (HFGW) radar. By displaying the change of signal energy on two dimensional time-frequency images based on time-frequency analysis, a new mathematical morphology method to distinguish target from nonlinear time-frequency curves is presented. The analyzed results from the measured data verify that with this new method the target can be detected correctly from wide Doppler spectrum.
  • HE Feng, WU Lenan
    The requirement and feasibility of the positioning system using digital television (DTV) broadcasting signals are analyzed. The principle of DTV positioning on the basis of frame synchronization is brought forward and the ranging characteristic is studied that the observables are asynchronously measured during the same epoch interval. The models of the pseudo-range observation and Doppler carrier phase integral are researched. The system observation and state equations are presented on the basis of the above models. The simulation results showed that DTV positioning technology could remarkably improve the precision of system state estimates using smoothing methods for positioning systems or integrated navigation systems. The DTV positioning that has a sub-meter level ranging error and meter level positioning accuracy can parallel with and even taken as a beneficial substitute for the tradition positioning technology.
  • FANG Liang, ZHAO Zhengyu, WANG Feng, SU Fanfan
    The real-time information of the distant ionosphere can be acquired by using the Wuhan ionospheric oblique backscattering sounding system (WIOBSS), which adopts a discontinuous wave mechanism. After the characteristics of the ionospheric echo Doppler spectra were analyzed, the signal preprocessing was developed in this paper, which aimed at improving the Doppler spectra. The results indicate that the preprocessing not only makes the system acquire a higher ability of target detection but also suppresses the radio frequency interference by 6 7 dB.
  • HE Fang, ZHAO Zhengyu, NI Binbin, ZHANG Yuannong
    A numerical model has been developed. Based on the numerical simulation results, the spatial effects of the ionosphere, mainly consisting of the change on electron density (ED) and electron temperature (ET), heated by the high frequency (HF) pump wave have been analyzed quantitatively. Results are presented as the space-time evolution regulation on the main parameters of the ionosphere resulted by the HF heating waves under the different heat-conditions, just as different regions, such as high latitude and mid-low latitude; different heating power or frequency, such as under-dense heating and over-dense heating and regions at different altitudes. The heating effects in different regions with different heating conditions have been presented in figures. Finally, some primary conclusions are given by comparing the simulation results with experimental observation.
  • ZHOU Yangzhong, HU Yuwen, HUANG Wenxin, ZHONG Tianyun
    The electrically excited synchronous motor (ESM) has typically small synchronous inductance values and quite low transient values because of the damper windings mounted on the rotor. Therefore, the torque and stator flux linkage ripples are high in the direct torque control (DTC) drive of the ESM with a torque and flux linkage hysteresis controller (basic DTC). A DTC scheme with space vector modulation (SVM) for the ESM was investigated in this paper. It is based on the compensation of the stator flux linkage vector error using the space vector modulation in order to decrease the torque and flux linkage ripples and produce fixed switching frequency under the principle that the torque is controlled by the torque angle in the ESM. Compared with the basic DTC, the results of the simulation and experiment show that the torque and flux linkage ripples are reduced, the maximum current value is decreased during the startup, and the current distortion is much smaller in the steady-state under the SVM-DTC. The field-weakening control is incorporated with the SVM-DTC successfully.
  • YIN Zhongke, WANG Jianying, Pierre Vandergheynst
    It is very slow at present to reconstruct an image from its sparse decomposition results. To overcome this one of the main drawbacks in image sparse decomposition, the property of the energy distribution of atoms is studied in this paper. Based on the property that energy of most atoms is highly concentrated, an algorithm is proposed to fast reconstruct an image from atoms  parameters by limiting atom reconstruction calculating within the atom energy concentrating area. Moreover, methods for fast calculating atom energy and normalization are also put forward. The fast algorithm presented in this paper improves the speed of the image reconstructing by approximately 32 times without degrading the reconstructed image quality.
  • LI Chao, WANG Wenling, HU Pengsong
    By using the coding properties and statistic properties of the plaintext, the differential properties of the key stream sequences generated by a nonlinear combined generator were analyzed. Then a differential attack algorithm on the nonlinear combined sequences was proposed. At last, an attack example adopting the differential attack algorithm was presented.
  • CHENG Yong, LU Wenjun, CHENG Chonghu, CAO Wei
    In this paper, a novel, small, and compact planar antenna for ultra-wideband (UWB) applications is proposed. The antenna is an extension of microstrip slot antenna technology. To achieve ultra-wideband characteristics, a tapered microstrip fork-shaped stub has been employed. A symmetric polygon wide slot has been placed on the antenna ground. The design was investigated numerically to obtain proper dimensions for the antenna and a prototype was constructed. The return loss, pattern and gain of the prototype antenna have been measured. The transient pulse signal fidelity has also been investigated by finite-difference timedomain (FDTD) method. Experimental results show that the proposed antenna design has promising characteristics for UWB applications.
  • QU Yanyun, ZHENG Nanning, LI Cuihua
    This paper proposes a novel airport detection method, which integrates the texture features and shape features of the airport. Eight texture features, such as the mean of the region, the deviation of the region, the smoothness of the region, the skewness of a histogram, the uniformity of the region, the randomness of the region, the mean of the gradient image and the deviation of the gradient image, are used to represent the features of the region. In this method, first the long lines are detected and the regions where the lines locate are segmented. Second, support vector machine (SVM) based on Gaussian kernel is used as a classifier which discriminates the runway from other candidate regions. Experimental results show that the error rate of the proposed method is lower than those of conventional methods which detect airport only by the shape feature of runway. The detection accuracy of the proposed method is nearly ten times higher than that of Liu s methods, and the method has favorable speed for a real-time system.
  • MAO Haiyang, XIONG Jijun, ZHANG Wendong, XUE Chenyang, SANG Shengbo, BAO Aida
    A measurement system was designed and established to test the piezoresistive properties of resonant tunneling diodes (RTDs). The current-voltage characteristic shifts of RTD at different stress states were detected. The experimental results demonstrate that the piezoresistive sensitivity of RTD is larger than 1×10-8 Pa-1. To accurately represent the piezoresistive properties of RTD, the current-voltage characteristic coherence of the same RTD was tested. According to the experimental results, the largest relative resistance shift of an RTD in the same measurement environment is less than 3%, of which 1% is caused by the testing apparatuses.
  • JIN Ronghong, YUAN Zhihao, GENG Junping, FAN Yu, LI Jiajing
    In order to overcome the drawbacks of standard particle swarm optimization (PSO) algorithm, such as prematurity and easily trapping in local optimum, a modified PSO algorithm is proposed, in which special techniques, as global best perturbation and inertia weight jump threshold are adopted. The convergence speed and accuracy of the algorithm are improved. The test by some benchmark problems shows that the proposed algorithm achieves relatively higher performance. Thereafter, the applications of the modified PSO in the radiation pattern synthesis of antenna arrays are presented.
  • TIAN Ye, SHENG Min, LI Jiandong
    This paper presents a novel distributed media access control (MAC) address assignment algorithm, namely virtual grid spatial reusing (VGSR), for wireless sensor networks, which reduces the size of the MAC address efficiently on the basis of both the spatial reuse of MAC address and the mapping of geographical position. By adjusting the communication range of sensor nodes, VGSR algorithm can minimize the size of MAC address and meanwhile guarantee the connectivity of the sensor network. Theoretical analysis and experimental results show that VGSR algorithm is not only of low energy cost, but also scales well with the network size, with its performance superior to that of other existing algorithms.
  • CHEN Bo, YU Xiangzhan, FANG Binxing, YUN Xiaochun
    There appear many Internet-scale worm incidents in recent years, which have caused severe damage to the society. It is clear that a simple self-propagation worm can quickly spread across the Internet. Therefore, it is necessary to implement automatic mitigation which can detect worm and drop its packet. In this paper, the worm s framework was first analyzed and its two characteristics were detected. Based on the two characteristics, a defending algorithm was presented to protect network. Experimental results verify that our algorithm is very effective to constrain the worm propagation and meanwhile it almost does not interfere in normal activity.
  • YANG Xiaoqing, HUANG Kama
    Microwave has been found as an efficient heating method in chemical industry. However, in present days the interaction between microwave and chemical reactions has not been deeply understood, which restricts a wider application of high power microwave in chemical industry. In this paper, the key problems of interaction between microwave and chemical reaction are investigated, such as complex effective permittivity of chemical reaction, simulation of microwave heating on chemical reaction and non-thermal effect of microwave, which will enhance further knowledge of the mechanism of interaction between microwave and chemical reaction. Moreover, such an analysis is beneficial for handling with difficulties in application of microwave chemical industry.