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    20 February 2008 Volume 35 Issue 1
      
    Original Articles
    Research on ISAR imaging of the complexly moving target based on the time-chirp distribution
    LI Ya-chao;SU Jun-hai;XING Meng-dao;BAO Zheng
    J4. 2008, 35(1):  1-7. 
    Abstract ( 2678 )   PDF (1524KB) ( 1460 )   Save
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    The change in chirp rate caused by the complex motion of the ship target deteriorates the azimuth focusing quality. This paper proposes a new imaging method based on TC-DechirpClean(DechirpClean searching method based on the time-chirp distribution), which makes use of the changing rate of scatterers’ chirp to search their chirp rate and change rate of the chirp rate in the time-chirp distribution plane. At the same time, we do FFT after compensating the higher-order phase term to acquire the information about the center frequency and magnitude of these scatterers according to the maximum magnitude criteria. Finally, we can reconstruct the echo signal and obtain an instantaneous ISAR image. The imaging result of real data confirms that this method can greatly improve an unfocused ISAR image caused by the change rate of the chirp rate.
    Optimal UWB pulse design method based on B-spline
    WANG Min;WU Shun-jun;LUO Feng
    J4. 2008, 35(1):  8-13. 
    Abstract ( 1904 )   PDF (809KB) ( 988 )   Save
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    The Ultra-Wideband (UWB) pulse waveform in communication need not only achieve orthogonality but also meet the Federal Communications Commission(FCC) spectral mask for the UWB commercial system. B-spline functions exhibit good approximation properties when serving as a basis in function learning. In this paper, a flexible UWB pulse waveform design method is proposed based on B-spline basis. The task of UWB pulse waveform design is represented as a constrained optimization problem, which takes the spectrum utility ratio as the target function, and takes orthogonality and spectral mask as the constraint. Subsequently the UWB pulse waveforms obtained in this way have the advantages of better spectrum utility ratio and complying with the FCC spectrum mask. The system of B-spline is also applicable to implemented circuits. Experimental results show the feasibility and merits of the proposed method.
    SAR image despeckling using statistical priors in nonsubsampled contourlet transform domain
    SUN Qiang;JIAO Li-cheng;HOU Biao
    J4. 2008, 35(1):  14-21. 
    Abstract ( 2401 )   PDF (1915KB) ( 1032 )   Save
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    A new despeckling scheme for synthetic aperture radar (SAR) images is proposed based on the adaptive shrinkage principle in the nonsubsampled contourlet transform (NSCT) domain. First, the statistical distributions of signal and speckle noise coefficient magnitudes in the NSCT-domain image subbands are effectively approximated by Gamma distributions and exponential distributions, respectively, which can make the shrinkage factor well adapt to the high redundancy of NSCT image subbands. A new set of directional neighborhood models is then proposed to calculate the prior ratio, making the shrinkage factor well adapt to the flexible directionality of NSCT-domain image subbands, thus enhancing the coefficient shrinkage performance. The experimental results on a real SAR image demonstrate that the proposed despeckling scheme can preserve the details while speckle noise is reduced. Compared with several classical despeckling methods, the new scheme has better edge preservation performance and backscattering coefficient preservation performance.
    Ambiguity analysis of the distributed micro-satellites SAR system
    YI Yu-sheng;LIU Xin;LIU Nan;ZHANG Lin-rang
    J4. 2008, 35(1):  22-26. 
    Abstract ( 1734 )   PDF (747KB) ( 1035 )   Save
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    A calculational method for ambiguities of long base-line distributed micro-satellites synthetic aperture radar system is proposed. The precision position of ambiguity dots is derived from micro-satellites’ real orbit information and the geometry of distributed micro-satellites. And the formulas are given to calculate both the range ambiguity ratio and azimuth ambiguity ratio, followed by the simulation analysis of the ambiguities of the Cartwheel formation and the Pendulum formation, which shows the ambiguity property of the distributed micro-satellites SAR System. The results of the simulation analysis indicate that the range ambiguities of micro-satellites will get close to that of the chief satellite as the decrease in distance between chief satellite and micro-satellites, and that the azimuth ambiguities of micro-satellites almost remain constant.
    Non-orthogonal joint diagonalization for blind source separation
    ZHANG Hua;FENG Da-zheng;NIE Wei-ke;XU Xian-feng
    J4. 2008, 35(1):  27-317. 
    Abstract ( 2510 )   PDF (604KB) ( 1256 )   Save
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    A novel cost function and a corresponding iterative algorithm for the non-orthogonal joint diagonalization of a set of eigen-matrices are proposed. The proposed cost function, improved from the classical least squares cost function that is the fourth function associated with the mixture matrix, is quadratic if two of the three parameter sets are fixed. Therefore, a new iterative algorithm based on the gradient descend method contains three sub-steps. In each sub-step, the closed solution is found by minimizing the cost function associated with one parameter group while fixing the others. Furthermore, global convergence is analyzed even in the presence of the estimation error of the eigen-matrix group. Finally, the results of the simulations illustrate that the proposed algorithm has better convergence performance, lower computational complexity, and can accurately retrieve the source signals from a set of received signals.
    Low complexity detection algorithm for the space-time bit interleaving coded modulation system
    LI Ying;GUO Xu-dong;WANG Xin-mei
    J4. 2008, 35(1):  32-36. 
    Abstract ( 2273 )   PDF (616KB) ( 1035 )   Save
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    A new low complexity iterative detection algorithm is proposed for the space-time bit interleaving coded modulation system. By utilizing the characteristics of the interleaving and the central limited theorem, the superstition of the transmitted signals at the receiver is first assumed as a Gaussian random variable. Therefore, the matrix inverse calculation can be avoided, which enables the proposed method to be used in a system with more transmitter antennas than receiver antennas. Under the previous assumption, P most significant symbol combinations are identified via the sequential principle to calculate the log likelihood ratio of each bit, which will be used by the iterative decoding. Compared with the available sequential algorithm, the proposed method reduces the complexity without sacrificing any performance.
    Immune algorithm for TSP with dynamic vaccination
    QI Yu-tao;LIU Fang;JIAO Li-cheng
    J4. 2008, 35(1):  37-42. 
    Abstract ( 2163 )   PDF (694KB) ( 1089 )   Save
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    To enhance the efficiency of artificial immune algorithms for Traveling Salesman Problem (TSP), we designed a dynamic vaccination strategy. The proposed vaccination obtains both single-vaccines and multi-vaccines by applying a linear complex intersecting operation on a random subset of the memory cell. The lengths of vaccines increase with iteration, which depresses the problem size and algorithm’s searching space. Compared with other vaccination strategies, the proposed strategy is unsupervised, which makes more accurate prediction of edges in the best tour and helps immune algorithms to maintain better solution paths.
    Spherical shell clustering based on quantum measurement
    YANG Xun1;XIE Wei-xin1;2;HUANG Jian-jun2
    J4. 2008, 35(1):  43-48. 
    Abstract ( 2224 )   PDF (861KB) ( 987 )   Save
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    Laboratory of Defense Technology, Shenzhen Univ., Shenzhen 518060， China)
    This paper proposes a method based on quantum measurement for spherical shell clustering. This method simulates the conscious cognition of the human brain using quantum measurement. It regards a sample set as an environment quantum ensemble which is measurable and the stimulus quantum system. In this thought, each sample is treated as a microcosmic state of quantum superposition. The stimulus quantum ensemble attracts the conscious attention and makes the cognition mechanism produce corresponding spherical shell surface operators by collapsing on microcosmic states in probability. A shell surface operator is applied to measure the environment quantum ensemble and the average measure value can be obtained which validates the operator. At the same time, a sample set on the shell surface will come forth. Quantum shell clustering has the ability of perfect initialization and auto-detection of the class number of clustering compared with fuzzy shell clustering. The quantum cognition thought,which integrates unconscious data-driving and conscious concept-driving in information-processing, can be further studied and applied in the other pattern analysis.
    Trajectory invariable-information target tracking algorithm with bearing-only measurement
    LIU Jin-mang1;2;JI Hong-bing1;ZUO Tao2
    J4. 2008, 35(1):  49-53. 
    Abstract ( 2631 )   PDF (640KB) ( 1305 )   Save
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    Force Engineering Univ., Sanyuan 713800， China)
    For the single sensor target tracking with bearing-only measurement, a novel trajectory invariable-information target tracking algorithm is proposed. A new cotangent theorem is deduced to solve the nonlinearity for bearing-only measurement. Both the heading angle calculation and the invariable-information of target trajectory are deduced to estimate the target bearing. For asynchronous bearing-only measurements from multiple sensors, a new two-sensor-with-bearing-only measurement target tracking method is brought forward, which estimates the target position by the geometry between sensors and target. Simulation results show that the new algorithm achieves a favorable tracking precision.
    Design of the fuzzy neural PID controller based on hybrid PSO
    ZHAO Jun;CHEN Jian-jun
    J4. 2008, 35(1):  54-59. 
    Abstract ( 2212 )   PDF (734KB) ( 1139 )   Save
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    Considering the problems of the linearity limit of PID control and the steady-state error in fuzzy, fuzzy PID control for it cannot easily obtain the control rules of the integral error, so a fuzzy neural PID controller which consists of a fuzzy neural network and a PID neural network is designed. The parameters of the controller are optimized by the mixed learning methods integrating the offline particle swarm optimization algorithm combined with chaos strategies of global searching ability, with the online BP algorithm of local searching ability. Simulation results show that the designed novel controller and the proposed optimization algorithm have obviously improved the performance of the transient state and steady state in the control processing. Compared with conventional PID, fuzzy control and fuzzy-PID control method, the new controller with the optimization method has good robustness and better performance. The new method breaks through the limit of linearity of PID control and expands its applications. It also provides a new reference for the combination of intelligent method and PID method.
    Model checking multirate hybrid systems
    ZHANG Hai-bin;DUANG Zhen-hua
    J4. 2008, 35(1):  60-648. 
    Abstract ( 1719 )   PDF (515KB) ( 971 )   Save
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    The model checking problem for initialized multirate hybrid systems is investigated, which is to check whether or not an initialized multirate automaton satisfies a property described by a hybrid interval temporal logic (HITL) formula. Firstly, some rules are defined to translate an HITL formula to an interval temporal logic (ITL) formula. Then, an equivalence relation over state spaces of multirate automata is defined to construct region automata from multirate automata. By constructing a labeled finite state automaton from a region automaton, the model checking issue for initialized multirate automata is translated to the same issue for ITL. Thus, by using the model checking algorithms for ITL and the translating rules defined in this paper, the model checking problem for initialized multirate hybrid systems can be solved.
    Design methods for non-fragile controllers for a class of uncertain impulsive hybrid systems
    CHEN Guo-pei1;LI Jun-min1;YANG Ying1;2
    J4. 2008, 35(1):  65-70. 
    Abstract ( 1704 )   PDF (572KB) ( 906 )   Save
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    A non-fragile control method for the impulsive hybrid system, whose discrete part is described by a finite state machine (FSM), is presented. It can avoid the effect of the parameter uncertainty of the controller. By concerning the stability of two parts, a concept of asymptotical stability for the whole hybrid system is proposed. Then, based on the optimal road idea, the discrete state can visit the desired set infinitely often along the optimal road by controlling the firing of discrete event, i.e., the FSM is stabilized. In addition, by using the multiple Lyapunov function, under the assumption that the additive gain variation of controller is bounded, the control gain is determined to stabilize the continuous subsystem by solving an LMI. So, the whole hybrid system is stabilized. A simulation example shows the effectiveness of the proposed approach. This approach can be used for computer integrated manufacturing systems and traffic management systems.
    Multicast routing algorithm for network coding
    WANG Jing1;LIU Jing-mei1;WANG Xin-mei1;YUAN Rong-liang2;LIU Xiang-yang3
    J4. 2008, 35(1):  71-75. 
    Abstract ( 2274 )   PDF (631KB) ( 1766 )   Save
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    Information Eng. College, Xi′an Univ. of Science & Tech., Xi′an 710054， China; 3. Military Comprehensive Information Network Teaching Office, Xi′an Commun. College, Xi′an 710106， China)
    This paper presents a new multicast routing algorithm for network coding. The algorithm searches the routing groups from source to each sink by using the Dijkstra reduction network. In the process of searching, link-sharing between different path groups is considered to decrease bandwidth resource consumption and improve load balance. Simulation results show that the routing algorithm is effective, and that its performance is closer to that of the minimum-cost multicast algorithm based on network coding. Finally, mathematical analysis indicates that the algorithm can reduce computation by 40％ at least.
    On the correlation analysis of product sequences
    XIAO Hong1;2;XIAO Guo-zhen1;WANG Xin-mei1
    J4. 2008, 35(1):  76-80. 
    Abstract ( 1889 )   PDF (494KB) ( 912 )   Save
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    Telecommunication Engineering Inst, Air Force Engineering Univ., Xi′an 710077， China)
    This paper presents a complete representation of auto-correlation functions of product sequences generated by one nonlinear combining function which consists of a finite number of l linear feedback shift registers (LFSR’s) with an AND gate logic, gives a formula for determining the Hamming weight of this product sequences in a period, and shows that the auto-correlation functions of such a kind of product sequences take l+1 values and that the main maximum value is high.
    Provable secure ID-based threshold signature scheme without random oracles
    ZHANG Le-you1;2;HU Yu-pu2;LIU Zhen-hua1;2
    J4. 2008, 35(1):  81-86. 
    Abstract ( 2534 )   PDF (522KB) ( 1031 )   Save
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    A (t, n) threshold signature scheme is presented and is provably secure in the standard model. The proposed construction possesses public verifiability and detects the dishonest participants by using Gennaro’s distributed key generation (DKG) protocol and the bilinear pairing. Its key generation does not require a trusted dealer in the key generation protocol and only runs an interactive protocol among n participants. This new scheme proves robust and secure against existential forgery under the adaptive chosen message attack, assuming that the computation Diffie-Hellman assumption holds.
    Study of the electronic structure of nitrogen doped 3C-SiC with first-principles calculation
    SONG Jiu-xu;YANG Yin-tang;CHAI Chang-chun;LIU Hong-xia;DING Rui-xue
    J4. 2008, 35(1):  87-91. 
    Abstract ( 2173 )   PDF (1148KB) ( 1323 )   Save
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    The electronic structures of the nitrogen doped(3×3×3)3C-SiC supercell are studied with first-principle calculation in which exchange-correlation energy is indicated by generalized gradient approximation, electronic wave functions are expanded in terms of a plane wave basis set and electron interaction is substituted by a ultra-soft pseudo-potential. The electrical structures of 3C-SiC with different nitrogen doping concentrations are calculated, and results show that the bottom of the conduction band of nitrogen doped 3C-SiC is taken up by N 2s electron states, that the top of the valence band has N 2p electron states, and that the bottom of the conduction band and the top of the valence band shift to a lower energy while the speed of the bottom of the conduction band is faster than that of the top of valence band, which leads to the band gap being narrower with the increase in nitrogen doping concentration.
    Preparation and characterization of K-doped p type ZnO films
    WU Jun;YANG Yin-tang
    J4. 2008, 35(1):  92-95. 
    Abstract ( 1543 )   PDF (842KB) ( 974 )   Save
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    Potassium(K), one of Ⅰ-group elements, is used as a dopant to prepare K:p-ZnO films deposited on single crystal Si(100) substrates by use of the radio frequency magnetron sputtering technique. The structures and electrical properties of the as-grown ZnO films are characterized by Hall, XRD, AFM and XPS measurements. The results indicate that the p-ZnO films show a typical preferred orientation of crystallites along with (002). When the substrate temperature and oxygen partial pressure are kept at 500℃ and 30％, respectively, the root mean square (rms) surface roughness of the p-ZnO thin films is 89.05nm approximately, and the hole concentration, mobility and resistivity are up to 5.45×1017/cm3, 1.96cm2/(V·s), and 5.91Ω·cm, respectively.
    Robust guaranteed cost control for the networked control systems
    ZHANG Xi-min1;2;LI Jian-dong1;ZHANG Jian-guo3
    J4. 2008, 35(1):  96-100. 
    Abstract ( 1994 )   PDF (564KB) ( 1110 )   Save
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    By means of the Lyapunov method and the robust control theory, a robust guaranteed cost control appproach is presented for the networked control systems (NCS), which is of the single-packet transmission and the bounded random communication time-delay. The NCS is modeled as a discrete uncertain time-delay control system. The effect of the random communication time-delay on the systems is converted to the unknown bounded uncertain parameter disturbance. A sufficient condition for the existence of the robust guaranteed cost control law for the systems is proved, and the design of the robust guaranteed cost state feedback controller for the NCS is solved by a set of linear matrix inequalities. Finally, a numerical example shows the effectiveness of the proposed methed.
    A new method for reduced-reference image quality assessment
    WANG Ti-sheng;GAO Xin-bo;LU Wen;LI Guang-dong
    J4. 2008, 35(1):  101-104. 
    Abstract ( 1838 )   PDF (754KB) ( 1293 )   Save
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    Based on the characteristic that image distortion results in the change of visual sensitivity coefficients of image, a new reduced-reference (RR) image quality assessment metric is proposed. Contourlet is applied to extract the visual sensitivity coefficients of the image. Summarizing the difference of visual sensitivity coefficients between the distorted image and the reference image, we can get the measurement of the distorted image. Experimental results illustrate that the proposed method has a good consistency with the subjective assessment of human beings, and can reflect the visual perception of the image effectively.
    Square attack on the 14-round block cipher SMS4
    ZHONG Ming-fu;HU Yu-pu;CHEN Jie
    J4. 2008, 35(1):  105-109. 
    Abstract ( 2010 )   PDF (532KB) ( 1004 )   Save
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    In order to make a new security evaluation for the block cipher SMS4, a certain plaintext is chosen to built a gamma set that contains three active words. Based on the character of the diversification of the active words in the round structure of SMS4, a balance word is found in the ninth round by observing the spread path of the balance words, and therefore a new 12-round distinguisher is constructed, by use of which a 14-round square attack is made on SMS4. In the attack 232chosen plaintexts are needed and the time complexity is about 296.5.Thus the 14-round SMS4 is not immune to the Square attack.
    Task scheduling based on trust mechanism of the L-fuzzy set in grid computing
    SUN Peng-gang1;QUAN Yi-ning1;LIU Jun-ping2
    J4. 2008, 35(1):  110-115. 
    Abstract ( 2022 )   PDF (602KB) ( 1240 )   Save
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    Mathematics and Information Science, Shaanxi Normal Univ., Xi′an 710062， China)
    A novel trust model based on the L-fuzzy set is established. It describes the trust between entities by linguistic variables, presents a formalized depiction based on context-free grammar and uses fuzzy operators to dispose trust levels. A new task scheduling algorithm L-FSTM-Min-Min (L-Fuzzy Set Trust Model-Min-Min) is brought out based on this model and Min-Min algorithm. This algorithm utilizes the triple I method to make fuzzy inference for multi-recommendation trust rules based on fuzzy logic and achieves comprehensive trust evaluation.Through the experiment by the GridSim simulator, results show that task completing time is obviously reduced and that the number of failed services is greatly decreased compared with the Min-Min algorithm in the same condition.
    Area-efficient high-speed VLSI design of the RS(255,239) decoder
    ZHANG Jing-bo1;DAI Xian-ying2;ZHANG He-ming2;HU Hui-yong1;JIA Da-zhong1
    J4. 2008, 35(1):  116-120. 
    Abstract ( 2279 )   PDF (716KB) ( 1139 )   Save
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    Based on the modified Euclid’s algorithm, a VLSI architecture is proposed, which only uses two folding calculating cells and three-stage pipeline processing architectures to improve its throughput. Also, a way is introduced to reduce the complexity and critical path delay of general finite multipliers by the transferring of field from the time domain to the composite domain. Based on the TSMC 0.18 standard cell library, the proposed RS decoder consists of about 20 614 gates for widely used RS(255,239) code, which reduces complexity by about 60％ compared with an existing architecture with systolic arrays when having the same error correction ability.
    Watersheds algorithm for relative potential energy
    ZHANG Li-li;YAO Yong;LIU Zhi-jing
    J4. 2008, 35(1):  121-124. 
    Abstract ( 1967 )   PDF (750KB) ( 1439 )   Save
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    A watersheds algorithm for relative potential energy is presented. The presented algorithm calculates the relative potential energy of watersheds and compares them with the preestablished thresholds to remove the unnecessary details and get the important contour information. This method is introduced on the basis of the fast watersheds model. As a result, over-segmentation is effectively restrained, region fusing is avoided and the efficiency improved accordingly. Experimental results have shown that, compared with the original region-fusing algorithm, the efficiency has increased by 14.3％, and that the over-segmentation phenomenon has been obviously improved.

    Mechanism study of the surface passivation effect on current collapse characteristics of AlGaN/GaN HEMTs

    YUE Yuan-zheng;HAO Yue;ZHANG Jin-cheng;FENG Qian
    J4. 2008, 35(1):  125-128. 
    Abstract ( 1789 )   PDF (518KB) ( 1062 )   Save
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    The effects of surface passivation on AlGaN/GaN highelectronmobility transistors (HEMTs) have been investigated. The surface passivation layer of Si3N4 is deposited by plasma enhanced chemical vapor deposition (PECVD). The currentvoltage and gatedrain diode characteristics of AlGaN/GaN HEMTs before and after passivation are analyzed. The current collapse under DC sweep has been significantly decreased after passivation and the existence of small dispersion of drain current is due to traps in the GaN buffer. The drain current increases after passivation, because surface passivation reduces the surface state density and so increases the sheet carrier density shown in Transmission Linear Model (TLM) measurement.
    Asymmetric digital watermarking algorithm based on DHT
    LIU Xiang-li1;KOU Wei-dong1;WANG Zhi-guo2
    J4. 2008, 35(1):  129-132. 
    Abstract ( 1809 )   PDF (554KB) ( 1029 )   Save
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    An Asymmetric digital watermarking algorithm is proposed, based on the discrete Hartley transform (DHT). The energy of the reference watermark is redistributed in the DHT domain to get embedding watermarks. They have the same correlation with the reference one. The embedding watermarks can be detected by the reference one, but not by one another. To decide whether the watermark is present or not, the detector compares the correlation coefficient with the decision threshold. In addition, the proposed algorithm deals with real numbers, which increases the computing efficiency compared with those dealing with complex numbers.
    Research on and evaluation of the reliability of a communication network management and control system
    HAN Wei-zhan;ZHANG Si-dong;SUN Yu
    J4. 2008, 35(1):  133-139. 
    Abstract ( 2194 )   PDF (739KB) ( 1335 )   Save
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    The reliability of a communication network management and control system, typically a complicated integrated system of software and hardware, has a significant effect on the communication network. A new approach to analyzing and evaluating the reliability of the system of a communication network is proposed. The whole system is divided into some layers such as subsystems, centers, software/hardware system and modules. The corresponding reliability models like series, parallel-in-weight, “n from k” vote and redundant model, etc. are established according to the falure criteria. The reliability of the software system can be obtained by the module analysis method and the reliability of a center can be obtained by integrating software and hardware system reliabilities. From bottom to top, the integrated realiability of the whole system can be found in the end. We also give the processing of integrated analysis and evaluation. The efficiency of our approach is validated through a real example simulation.
    Research on the bistatic RCS characteristic of aircraft
    HUANG Pei-lin;JI Jin-zu;WU Zhe
    J4. 2008, 35(1):  140-143. 
    Abstract ( 2152 )   PDF (1383KB) ( 1193 )   Save
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    The RCS of aircraft at different bistatic radar angles is gained to investigate the electromagnetism scattering characteristic of the multi-station and bistatic radar.This method uses an efficient method for revolving the target and fixing bistatic radar angle to avoid multiple picketage. Three bistatic RCS characteristics, which are symmetry, similarity and weak coupling, are found by comparing the target RCS with different bistatic radar angles. Some results are obtained as follows: stealth technology of monostatic radar could realize the stealth purpose by changing the electromagnetism scattering space distribution and making the intense wave crest go out of the important detect region, while techology of bistatic radar that intercepts the intense wave crest which is out of the important detect region is mainly used to meet the anti-stealth requirement.Both of the main threatening bistatic radar angles and the entire intense wave crest should be considered to estimate the target bistatic stealth characteristic.
    Analysis of two novel spherical helical antennas
    ZHANG Hou1;YIN Ying-zeng2;XIA Dong-yu3
    J4. 2008, 35(1):  144-147. 
    Abstract ( 2111 )   PDF (932KB) ( 1256 )   Save
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    Antenna and EM Scatterng, Xidian Univ., Xi′an 710071， China; 3. P.O.B.2863, Beijing 100085， China)
    Two novel spherical helical antennas are designed by projecting the planar equiangular spiral antenna onto the surfaces of hemisphere and partial sphere. Their radiation properties are analyzed by the moment method with the curved basic and testing function, and the curves of the VSWR, gain, polarization and pattern vs. frequency are also given, respectively. It can be seen that the circular polarization band of the novel hemispherical helical antenna is broader.The gain curve of the partial spherical helical antenna is flatter and the structure is simpler.
    Design and analysis of a verifiable secret sharing scheme
    LI Hui-xian1;CAI Wan-dong1;PEI Qing-qi2
    J4. 2008, 35(1):  148-151. 
    Abstract ( 1911 )   PDF (490KB) ( 1002 )   Save
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    As the further expansion of the multiple secret sharing scheme, the multi-secret sharing scheme can share any number of secrets in one sharing session. In order to prevent the secret dealer’s and the participant’s cheating attacks like those in the existing multi-secret sharing schemes, a new verifiable threshold multi-secret sharing scheme is proposed. Each participant’s secret shadow is selected by himself and it can be transmitted to the secret dealer over a public channel. The shadow can be used in multiple sharing sessions without the need to be updated. At the same time, it is allowed to check whether each cooperative participant and the secret dealer have taken a legal action or not. The security of the proposed scheme is based on that of Shamir’s secret sharing scheme and that of the ECIES cryptosystem, and the difficulty in solving the elliptic curve discrete logarithm.
    Neural networks based on the genetic algorithm and its application in mechanical engineering
    LIU Dao-hua1;2;YUAN Si-cong1;WANG Jin-you2;ZHAO Jin-chang1
    J4. 2008, 35(1):  152-156. 
    Abstract ( 2572 )   PDF (606KB) ( 1100 )   Save
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    Authors take advantage of the genetic algorithm (GA) to automatically obtain structures, weights and bias of neural networks (NN). A classified coding scheme is presented to get modeling parameters of an NN. Then a practical fitness function along with a new method that can automatically adjust the number of hidden nodes and connection weights according to the individual fitness values is described in detail. The proposed method is applied to calculate the parameters of a manipulator with a freedom of degree 2. Simulation result is compared with data obtained from practical experience and the back propagation(BP) learning algorithm. Comparison study indicates that the proposed method has many advantages such as higher simulation accuracy, less resource utilization and higher computational efficiency.
    Radio telescope pointing model based on the generalized extended interpolation correction method
    KONG De-qing1;2;SHI Hu-li1;2;ZHANG Xi-zhen1;ZHANG Hong-bo1
    J4. 2008, 35(1):  157-161. 
    Abstract ( 1764 )   PDF (913KB) ( 976 )   Save
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    A new pointing error correction model of the radio telescope based on generalized extended interpolation is presented. After the linear pointing correction, the surveying region is divided into spherical Delaunay triangulations, and the whole smooth pointing correction surface is produced by using the high-accuracy generalized extended interpolation approximation method. In every Delaunay triangle, the border points of segmentation can meet the interpolation condition, and by using the surrounding information of joint (including the inner joint) sufficiently, the piecewise best-fitting is obtained. Simulation results using experimental pointing data of the 50m radio telescope show that this model improves the pointing forecast precision by 30.3 percent compared with the linear pointing model.
    QoS-aware cooperative diversity protocol for wireless LANs
    LI Yi;JI Hong
    J4. 2008, 35(1):  162-166. 
    Abstract ( 2166 )   PDF (557KB) ( 1082 )   Save
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    By introducing quality of service(QoS) attributes into cooperative communications, a QoS-aware cooperative diversity protocol is proposed. According to different services, cooperative diversity is invoked only if the minimum data rate required to have a successful transmission cannot be achieved. Based on user-specific QoS requirements, partners are determined cautiously. Analytical and simulation results indicate that the QoS-aware cooperative diversity protocol can avoid the negative effect of error propagation in cooperation and greatly improve the system throughput.
    A novel GPS frequency estimation algorithm in high dynamic circumstances
    ZHU Yun-long;LIU Zhong-kan;YANG Dong-kai;ZHANG Qi-shan
    J4. 2008, 35(1):  167-170. 
    Abstract ( 2264 )   PDF (537KB) ( 1109 )   Save
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    Low estimation precision and high loss-of-lock threshold are the two important drawbacks of the extended Kalman filter (EKF) which is the widely used GPS frequency estimation algorithm in high dynamic circumstances, caused by linearizing all nonlinear models. To resolve the problems of EKF, the unscented Kalman filter (UKF) which is a new kind of linear filter is introduced to estimate frequency. Instead of the linearization steps required by the EKF, a series of Sigma points and unscented transform (UT) are used to predict and update the state vector and covariance. Simulations indicate that the estimation precision of UKF is greatly improved compared with that of EKF, that the loss-of-lock threshold is about 1dB lower than that of EKF, and that the estimation performance is improved.
    Optimal joint design of adaptive coded modulation and ARQ
    CHENG Peng;ZHANG Zhao-yang;HUANG Hui;QIU Pei-liagn
    J4. 2008, 35(1):  171-174. 
    Abstract ( 2028 )   PDF (528KB) ( 1054 )   Save
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    A cellular downlink system combining AMC and ARQ is considered. The BS obtains the channel state information through the feedback of the receiver, and then adaptively chooses the modulation and coding method at the physical layer to maximize the system spectrum efficiency. At the same time, ARQ at the data link layer is also adopted to improve the robustness performance. Based on this cross-layer system, the problem of spectral efficiency maximization for non-realtime services is studied, that is, how to maximize the spectral efficiency by optimally choosing the AMC parameters under the average delay constraint. First, the above cross-layer system is modeled under some reasonable assumptions. Then, the studied problem is formulated as a convex optimization one. Finally, this problem is solved with the classical Lagrangian method. Numerical simulations show that our proposed method is optimal.
    Inverse kinematic research based on a new type of reconfigurable robot
    WEI Yan-hui;ZHAO Jie;ZHU Yan-he;CAI He-gao
    J4. 2008, 35(1):  175-182. 
    Abstract ( 1765 )   PDF (503KB) ( 1027 )   Save
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    The complicated work configurations of reconfigurable robots make it quite difficult to solve the problem of inverse kinematics, which directly affects the real time control and application of reconfigurable robots. In this paper, a new modular modeling method is proposed, and by using this new method, the kinematical model for a robot can be built immediately. This is a method that decomposes the work configurations of a robot at the target position into finite configuration planes, and by describing the workspace of these configuration planes, the orientations and positions of these planes can be matched to find the numerical solutions to a robot. The applicability of this method is proved through the kinematical simulation of an eight DOF robot built using elementary modules.
    Study of heat load forecasting based on the maximum entropy principle
    CHEN Lie;QI Wei-gui;DENG Sheng-chuan
    J4. 2008, 35(1):  183-188. 
    Abstract ( 1606 )   PDF (508KB) ( 999 )   Save
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    According to the characteristics of architecture heat supply and the demands for energy-saving control, load forecasting based on the maximum entropy method is proposed. By using the least square fitting and the pretreatment approach, the historical random load series collected from the heat supply station are separated into the certain part and the random part. Then the load series is dealt with by the auto-correlation method and the maximum entropy method respectively. Comparing the results of these two methods shows that the load forecasting based on the maximum entropy theory can meet the demands for heating energy-saving control in terms of the forecasting accuracy, auto-adaptive and real-time ability better.
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