Sep 2008, Volume 3 Issue 3

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  • GU Jin
    Computational methods have greatly expanded our understanding of complex gene regulations in a systematic view. The rapid progress in molecular biology and high-throughput bio-techniques is providing new opportunities and challenges for the computational analysis of gene regulations.
  • BI Jianning, PENG Tao, LI Yanda
    Alternative splicing (AS) has been shown to be frequently present in human tumors. Specifically, it has been observed in some experimental studies that multi-exon skipping (MES) events often appear in tumorous tissues. Prompted by this observation, we conducted a genome-wide analysis of MES events to investigate their association with tumors. The results show that MES events are more likely associated with tumors than single-exon skipping (SES) and the degree of association increases with the number of skipped exons. Furthermore, MES events are found to be less conserved than their SES counterparts, which provides additional evidence for our results because disease-associated AS events should be eliminated during evolution. Interestingly, these differences still existed even after comparison of MES and SES events with similar-length skipped regions. These results demonstrate that MES events may be associated with tumors and suggest that MES isoforms might be useful in cancer diagnosis.
  • WANG Ying, GAO Xinbo
    To improve the detection of mass with appearance that borders on the similarity between mass and density tissues in the breast, an support vector machine classifier based on typical features is designed to classify the region of interest (ROI). Furthermore, relevance feedback is introduced to improve the performance of support vector machines. A new mass detection scheme based on the support vector machine and the relevance feedback is proposed. Simulation experiments on mammograms illustrate that the novel support vector machine classifier based on typical features can improve the detection performance of the featureless classifier by 5%, while the introduction of relevance feedback can further improve the detection performance to about 90%.
  • WANG Jiangtao, YANG Jingyu
    In visual tracking, integrating multiple cues will increase the reliability and robustness of the tracking system in situations where no single cue is reliable. In this paper, a novel multi-cue based tracking method is presented under the particle filter framework. Considering both practical distance and Bhattacharyya distance between particles and the target, a parameter called relative discriminant coefficient (RDC) is designed to measure the tracking ability for different features. Multi-cue fusion is carried out in a reweighing manner based on this parameter. Experimental results demonstrate the high robustness and effectiveness of our method in handling appearance changes, cluttered background, illumination changes and occlusions.
  • LIU Yang, JIA Yingmin
    In this paper, the conventional tracking control problem is expanded to first-order multi-agent systems, which can be solved by directly guiding any agent in the group. The following three kinds of desired motions are considered for all agents to track: 1) stillness in space, 2) variable motion with known acceleration, 3) variable motion with partly unknown acceleration. Specifically, fixed networks with time delays and switching networks without delays are both considered in case 1). Switching networks with and without time delays are both studied in case 2), while for 3), switching networks without delays are mainly investigated. A numerical simulation example is included to illustrate the results.
  • YU Zhenhua, CAI Yuanli, YU Zhenhua, XU Haiping
    As ?-calculus based on the interleaving semantics cannot depict the true concurrency and has few supporting tools, it is translated into Petri nets. ?-calculus is divided into basic elements, sequence, concurrency, choice and recursive modules. These modules are translated into Petri nets to construct a complicated system. Petri nets semantics for ?-calculus visualize system structure as well as system behaviors. The structural analysis techniques allow direct qualitative analysis of the system properties on the structure of the nets. Finally, Petri nets semantics for ?-calculus are illustrated by applying them to mobile telephone systems.
  • MA Qinghua, YANG Luxi, HE Zhenya
    For the frequency selective and time variant multiple-input multiple-output (MIMO) channel model taking into account transmitting and receiving antenna correlation, the diversity of space-time-frequency coded broadband orthogonal frequency division multiplexing (MIMO-OFDM) system is analyzed. Based on the average pairwise error probability (PEP), the design criterion of space-time-frequency code (STFC) is expanded. For a given STFC, it is found that the achievable diversity order is related to the transmitter and the receiver correlation matrix as well as the time correlation and frequency correlation matrix. The maximum available diversity of STFC over the correlation channel is Lrank(P)rank(Q)rank(RT). The space-time code and space-frequency code are special cases in our approach. Simulation results validate the findings.
  • ZHANG Chengwen, ZHANG Zhongzhao, MENG Weixiao
    To minimize transmitting power, an adaptive resource allocation algorithm is proposed for multi-user multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) downlink with correlated channels, which, based on the user’s grouping according to their spatial correlations, combines the shared manner and the exclusive manner to allocate sub-carriers. Between different groups the shared manner with a null steering method based on group marginal users is applied, whereas within a group the exclusive manner is applied. The simulations show that the power efficiency and spectral efficiency are improved; the base station transmitting antenna number and the computational complexity is decreased.
  • XIA Bin, WANG Wenbo, XIA Bin
    Direction of arrival (DOA) estimation is one of the key technologies in smart antennas in the direct sequence ultra wideband (DS-UWB) system. Traditional DOA estimation methods based on narrow-band signals are not suitable for such system. Therefore, a fourth-order cumulant-based estimation method of DOA for DS-UWB signal is proposed. This method is set on the frequency domain model of DS-UWB array signal. Simulation results show that the algorithm is effective and can guarantee adequate estimation accuracy.
  • ZHU Xiaoliang, DU Xu, ZHU Xiaoliang
    In order to solve the problems of link layer retransmission and packet fragment strategies for IEEE 802.11, this paper proposes a variable packet TCP-friendly rate control (VPTFRC) scheme for streaming media transmission over wireless local area network (WLAN) by researching on the policy of packet size adjustment in transport layer based on the minimum retransmit-delay constraint. Unlike other proposals, this process considers the impact of wireless packet error ratio (PER) on the packet size adjustment and the performance of rate control. Simulation results demonstrate that our proposed process can simultaneously achieve higher throughput, better fairness, shorter transmission delay and less jitter than TFRC. Among them, the ratio of delay, jitter and packet loss rate can reach a maximum improvement ratio of 58%, 42% and 85% respectively.
  • LI Bin, ZANG Yunhua, DENG Yu, HUANG Shanguo, GU Wanyi
    A novel prefigured-cycle (P-Cycle) algorithm was proposed to improve the protection success ratio for asymmetric traffic in mesh optical networks. The proposed algorithm was simulated in a Pan-European COST239 network environment under an asymmetric dynamic traffic model. The experimental results show that the proposed algorithm has lower capacity redundancy and higher utilization rate of configured resources than traditional P-Cycle methods. Network performance can be improved when implementing this algorithm under single-link failure circumstances. The system behavior is analyzed under different traffic volumes and the configuration strategy is also investigated for the heavy-load and light-load networks respectively.
  • LU Yiyi, HE Chen, JIN Ruxiang
    A new routing and wavelength assignment method applied in hierarchical wavelength division multiplexing (WDM) networks is proposed. The algorithm is called offline band priority algorithm (offline BPA). The offline BPA targets to maximize the number of waveband paths under the condition of minimum number of wavelengths, and solve the routing and wavelength assignment (RWA) problem with waveband grooming to reduce cost. Based on the circle construction algorithm, waveband priority function is introduced to calculate the RWA problem. Simulation results demonstrate that the proposed algorithm achieves significant cost reduction in WDM network construction.
  • YU Tao, LI Xin, CHEN Shanzhi, QIN Zhen
    A new deflection routing scheme is proposed to overcome the drawback of existing deflection routing scheme that cannot handle node failure and suffer from routing loops. A new algorithm for computing the backup shortest path tree (SPT) is proposed and a set of procedures are defined for utilizing the backup SPT in case of node or link failure. The failure can be handled swiftly and the backup routes are guaranteed to be loop-free. Experimental results show that the backup routes calculated by proposed scheme are close to the optimal routes by totally re-computing.
  • MA Weiju, FENG Dengguo
    A new clock-controlled key-stream generator is proposed in this paper. The generator is composed of three shift registers: two clock-controlled linear feedback shift registers, A and B, and one clock-controlled nonlinear feedback shift register C. The clock-controlled information is from two bit strings of feedback shift register C. The times A and B shift are according to the Hamming weights of the two strings, respectively. The period, the linear complexity and the k error linear complexity of the key-stream generator are studied, and the security of it is analyzed.
  • YU Yan, OU Jinping
    In order to validate the feasibility of applying wireless sensing technique to structural monitoring of offshore platform, the experiment of wireless sensor network on offshore platform is presented in this paper. First, wireless sensor network and its topology structure is put forward, and the design of sensor nodes, base station, communication protocol is discussed according to self-developed wireless sensor network. Second, true offshore platform and its experimental model are introduced. Finally, wireless sensing experiment for offshore platform structure is completed and the analysis of the experimental result is given. The research shows that wireless sensor network applied to offshore platform can reflect the vibration of the structure; the sensor nodes are fixed and removed expediently, which saves the cost of signal line as well as installation time.
  • FU Weihong, LIU Nai'an, ZENG Xingwen, YANG Xiaoniu
    Most blind source separation algorithms are only applicable to real signals, while in communication reconnaissance processed signals are complex. To solve this problem, a blind source separation algorithm for communication complex signals is deduced, which is obtained by adopting the Kullback-Leibler divergence to measure the signals’ independence. On the other hand, the performance of natural gradient is better than that of stochastic gradient, thus the natural gradient of the cost function is used to optimize the algorithm. According to the conclusion that the signal’s mixing matrix after whitening is orthogonal, we deduce the iterative algorithm by constraining the separating matrix to an orthogonal matrix. Simulation results show that this algorithm can efficiently separate the source signals even in noise circumstances.
  • LI Hongyan, MA Jianfen, LI Deng'ao, WANG Huakui
    This paper introduces the fixed-point learning algorithm based on independent component analysis (ICA); the model and process of this algorithm and simulation results are presented. Kurtosis was adopted as the estimation rule of independence. The results of the experiment show that compared with the traditional ICA algorithm based on random grads, this algorithm has advantages such as fast convergence and no necessity for any dynamic parameter, etc. The algorithm is a highly efficient and reliable method in blind signal separation.
  • QI Lei, CUI Xiang
    It is vital to study the electromagnetic coupling to shielded cable for improving electromagnetic anti- interference ability of secondary equipment in a substation. As a hybrid of method of moment (MoM) and transmission line method, a frequency domain model is put forward to study the near field coupling to shielded cable due to the switching operation in substation. Compared with the results of EMTP, the proposed method has been proven correct. Furthermore, this method overcomes the disadvantage of EMTP, which is only applicable for transient analysis of parallel conductors. As an example, the presented method is applied to evaluating the electromagnetic interference (EMI) to the shielded cable, whose shield is grounded at both ends, due to the switching operation in 500 kV air insulation substation (AIS).
  • SONG Haifeng, CHEN Zhiyu, SONG Haifeng
    In this paper, the common-mode radiation characteristic of the connection between a cable and a conductor is analyzed by the electric field integral function (EFIF) and the method of moment (MoM). The RWG basis function is adopted as the conductor basis function, the pulse basis function as the wire basis function and the juncture employs Costa basis function. A scheme of singular region separation is proposed to overcome the integration singularity of juncture matrix elements. Some new conclusions of the common-mode radiation characteristics with the metal case are obtained by numeration.
  • MAO Junhong, LUO Junhang, JIANG Qiang, XIE Youbai, JIANG Qiang
    An iron-less single side permanent magnetic linear motor structure is presented, and two-dimensional analytical formulae for its magnetic field are deduced to design the types of magnetic arrays, the thickness of permanent magnet, and the duty ratio of magnet arrays, etc. With certain design parameters, conventional arrays are used instead of a piecewise Halbach arrays, and the machining and assembling of the motor are greatly simplified. Calculation results coincide with that of ANSYS. The analytical formulae can be used in designing cored linear motors by modifying boundary conditions. A linear motor driven bench with a single degree of freedom is realized, where the travel reaches 27 mm, the mass of the moving parts is 1.4 kg, and the maximum acceleration is 11.5 m/s2.
  • LIU Jianfang, YANG Zhigang, ZENG Ping, FAN Zunqiang
    A new precision rotary piezoelectric (PZT) actuator is proposed to improve its drive performance. Based on piezoelectric technology, the actuator adopts the principle of bionics, with a new method of stator inner anchor/loosen/rotor outer drive and a distortion structure of a thin shelf flexible hinge. This structure improves the stability of the anchor/loosen and step rotary. Its characteristics are evaluated by finite element analysis. The experiment shows that the new rotary PZT actuator works with higher frequency (40 Hz), higher speed (325 ?rad/s), wider movement (360°), high resolution (1 ?rad/step) and high torque (30 N·cm). The novel actuator can be applied in wide movement and high resolution driving devices such as those for optics engineering, precision positioning and some other micro-manipulation fields.