Table of Content

31 January 2005, Volume 23 Issue 1

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Articles

The Research of Stratospheric Balloon Positioning by the Loran-C Augmented Beidou System

DUAN Fang, LIU Jian-ye, LIN Xue-yuan

2005, 23(1):  1-5. 

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A stratospheric balloon positioning method using the Loran-C augmented Beidou system is proposed. The systems working principle is elucidated and the positioning algorithm of searching for the shortest distance between two curves is given.The algorithm was simulated using Matlab software, and it's real-time performance and position error are analyzed.The result shows that the algorithm has good real-time performance and that positioning precision is more sensitive to Loran-C measurement error than to double-star measurement error.It is found that when the Loran-C error and double-star error grow simultaneously, the position error may be equivalent to or even smaller than the error caused only by Loran-C error alone.The positioning precision has a relationship with the choosing of Loran-C chain.The algorithm is also suitable for the positioning of other air/ground/sea vehicle.

Practical Metrics for Z Specifications

WU Fang-jun, YI Tong

2005, 23(1):  6-11. 

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The cost of correcting or remedying errors would increase by geometric series at the later of software development.Thus the quality of formal specifications becomes one of the key issues and difficulties.But little work has been done on how to measure the quality of formal specifications till now.To solve these problems, a suite of metrics to measure schemas of formal specification language Z is proposed.The metrics consider schema decoration, schema inclusion, schema type, and schema calculus.According to these metrics, some problems can be found and further overcome at the early life cycle, which reduce cost greatly.Besides, an effective estimation of the system can be made.

Nonlinear Exponential Reduced-Order Observers Based on Differential Riccati Equation

ZHU Fang-lai

2005, 23(1):  12-15. 

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The problems of observer design for nonlinear systems with linear output are discussed in this paper. Under the assumption that a differential Riccati equation is solvable, an exponential reduced-order observer is developed by means of coordinate transformation and the gain matrix of the proposed observer depends on the solution of the differential equation.The simulation results show that the performance of the proposed reducedorder observer is good.

The Surface Model Based Intelligentized Plastic Injection Molding Simulation

LI De-qun, ZHOU Hua-min

2005, 23(1):  16-19. 

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There are two great improvements in the development of injection molding simulation:(1) The surface model based simulation.By using the surface model to replace the conventional mid-plane model, the bottleneck of traditional CAE softwares is broken through;(2) The knowledge-based simulation.By taking full advantages of artificial intelligence and expert system technologies in the CAE system, the initialization, evaluation and optimization of designs can be accomplished with the guidance of CAE.This greatly improves the utility and efficiency of CAE.

The Statistical Characteristics of the Instantaneous Polarization Projection of Partially Polarized Waves

WANG Xue-song, DENG Yong, LI Yong-zhen, DAI Da-hai

2005, 23(1):  20-25. 

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The statistical characteristics of the instantaneous polarization projections (IPP) of partially polarized waves are studied on the basis of the theory of instantaneous polarization.A novel concept of the distance between an IPP and an expected polarization track is presented.It is essentially a measure of the distance between two polarization signals' IPPs in the metric space.Under the normal hypothesis, the probability density function (PDF) of this distance is derived.It's also proved that this distance obeys the normal distribution approximately when the number of the samples of a partially polarized wave is large enough. These results are of great importance to polarization signal detection, estimation and filtering.

A Symbolic Dynamics Based Method for Noise Reduction in Chaotic Sequence

LI Hui, XU Pei-xia

2005, 23(1):  26-30. 

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Based on symbolic dynamics, a method for noise reduction of unimodal map chaotic sequence is presented.The Markov process model of symbolic dynamics is discussed and from this model a maximumlikehood method based on the Viterbi algorithm for the noise reduction is derived.And by using symbolic dynamics, the performance of this noise reduction method is analyzed.It is shown that the analysis agrees with the simulation result.The method and its analysis can be applied in noise reduction of chaotic communication.

A Robust Scheme for Contour Extracting and Tracking

YANG Xiao-hui, LI Zhong-ke, WU Le-nan

2005, 23(1):  31-36. 

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A new scheme is proposed to extract and track the object contour automatically in this paper, it combines the active contour based on the gradient vector flow(GVF-Snakes) and the genetic algorithm (GA) based on the fine-grained model.On the one hand, the GVF-Snakes is improved by using the edge criterion instead of the complex energy computation to reduce its complexity and speed up its search.On the other hand, the selection of the array of the reference points by the GA enhances the extracting performance of the extreme concave contours and noise-disturbing contours.Experiment on the synthetic and natural images demonstrate its robustness and accuracy.

The Dispersion Characteristics of EBG Structure Consisting of Uniaxial-Chiral Medium

ZHENG Long-gen, ZHANG Wen-xun

2005, 23(1):  37-40. 

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A general model for analyzing the electromagnetic band gap (EBG) structure with bi-anisotropic medium is established by using the plane wave expansion method.An EBG structure consisting of triangular la ttice of air cylinders embeded in a uniaxial chiral medium is simulated.The results show that, when the dielectric constants in the cross section remain the same, an EBG structure with a uniaxialized chiral host (permittivity is positive uniaxial, others are isotropic) possesses a wider complete band gap than the one with an isotropic chiral host.This discovery provides an alternative option for the potential electromagnetic application of the EBG structure.

Contour Extraction for Medical Images Based on the Combination of the Statistical Method and Active Contour Models

CHEN Zeng-sheng, ZHOU Kang-yuan, LI Chuan-fu, HU Yao-hui, HUANG Dan, WANG Qing-lin

2005, 23(1):  41-44. 

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The paper proposes a method of images contour extraction which combines the statistical method and active contour models(ACM).To choose the contour points of points distribution models automatically, the minimum description length was chosen as the object function.A typical contour model is obtained from an image training set.After the initialization of a new image's ACM contour, the typical contour mentioned above is used as the deformation constraint to extract the nearly optimum contour.The experiments with the real images show the effectiveness of this method in comparison with the traditional active contour models method.

A Rapid Acquisition Method of UWB Wireless Communication

XU Chi, YIN Hua-rui, XU Pei-xia

2005, 23(1):  45-50. 

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The UWB signal acquisition circuit based on the analog PLL is improved.A method to obtain the signal clock is studied, and then on the base of this circuit a binary search algorithm is proposed to obtain the pulse position and the timing of the signal frame.The circuit of this method can be realized easily.The simulation results and analysis indicate that it has the merits of precise timing and fast acquisition.It is of considerable reference value for the realization of UWB communication.

A Research on the Algorithm of the Vehicular Short-Wave Single-Channel Direction Finding System

WANG Xiao-dong, DAI Xu-chu, XU Pei-xia

2005, 23(1):  51-55. 

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Using the traditional algorithm, the vehicular short-wave single-channel direction finding devices can not cope with the single side band signals satisfactorily.This article discusses the vehicular short-wave single-channel direction finding system and gives a new direction finding algorithm based on signal spectrum correlation, to improve the system's performance to when coping with single side band signals.

The Adaptive WMSA Channel Estimation Based on Doppler Shift Estimation

HUA Jing-yu, SHENG Bin, MENG Qing-min, YOU Xiao-hu

2005, 23(1):  56-60. 

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The classical channel estimation method is linear interpolation, and the variation rate of the channel corresponds to its maximum Doppler shift.Hence, the interpolation length can be decided by the estimated Doppler shift.An adaptive weighted multi-slot average channel estimation method is thus proposed to improve channel estimation accuracy.

A Partial Scan Algorithm for BIST Based on Structure Analysis and Testability Analysis

XIE Yong-ming, LI Rui, YANG Jun

2005, 23(1):  61-66. 

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A partial scan algorithm for BIST, which combines the structure analysis and testability analysis, is presented in this paper.The basic principle and implementation of the algorithm are analyzed in detail.The fault simulation experiments on ISCAS89 benchmark circuits by means of this algorithm are made, and the results are compared with the full scan algorithm and the partial scan algorithm based only on the structure analysis.Compared with the full scan algorithm and the partial scan algorithm based only on the structure analysis, our partial scan algorithm can greatly reduce the test time with very close or even greater faults coverage and mess area than the full scan algorithm.

The Security Analysis for WLAN TKIP Protocol

SONG Yu-bo, HU Ai-qun, CAI Tian-you

2005, 23(1):  67-70. 

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As an expansion of LAN, the WLAN reduces the cost of building a network infrastructure and enables the users to enjoy the mobile services.The 802.11 standard includes a wired equivalent privacy (WEP) protocol, which is used to protect communications from eaves dropping.Several serious security flaws in this protocol have been discovered.To cope with this problem, IEEE802.11i Group proposed adapting TKIP protocol to enhance the WLAN security.In this paper, through analyzing TKIP protocol, concrete security analyses of TKIP protocol are made.It was shown that although TKIP did indeed increase security and result in significant, provable security gains, but it still failed to meet the need of users in a WLAN environment.

Clustering XML Documents Based on a Structural Summary Tree

LIANG Zuo-peng, WU Wen-ming, DONG Yi-sheng

2005, 23(1):  71-74. 

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An approach for calculating the structural similarity between XML documents is proposed in this paper.The structural information of an XML document is captured with a structural summary tree (SST).By encoding elements as digital numbers, a SST is transformed to a digit-labeled tree.Digital numbers at different tree levels are concatenated to form a vector after the normalization process.Consequently, each XML document is represented as an m-dimension vector.The GA-based clustering algorithm is adopted since it is able to provide good results irrespective of the starting configuration.Experimental results show the effectiveness and scalability of the approach.

The GenExtractor: A Web-Based Bioinformation Mining System

XIN Jian, LU Wei, ZHU Jing-de, WANG Yi-fei

2005, 23(1):  75-81. 

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GenExtractor is a new Web-based bioinformaition mining system.It can be employed to search for genes with specialized function in the designated chromosome region by mining biology sequence data and gene express data in the online biology databases through the Internet.The molecular biologists can apply this system to identify the candidate genes and gather the relevant information.The actual effect of this system has been validated by screening the Human DNA repair genes.

The Analysis and Experiment of Determining the Stable Zone in a Magnetically Fluidized Bed

WANG Ying-hui, GUI Ke-ting, SHI Ming-heng

2005, 23(1):  82-85. 

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Basing on the analysis of the forces on magnetic particles, applying the basic theory of the fluidized bed and analyzing by the dimensionless method, the paper shows that the stable zone in a magnetically fluidized bed mainly depends on Re, Ar, and Er, which are primary factors to show the fludized characteristics of the magnetically fluidized bed.A relationship to express the ratio of minimun bubbling velocity to initial fluidized velocity is obtained through the processing of experimental data.Compared with the results reported before, the relationship proves to be correct on the condition of moderate intensity of the magnetic field, and the error of all experimental and calculated data is less than 8%.

An Analysis of the Runoff Change Law Based on the Maximum Entropy Spectrum

ZHAO Xue-hua, HUANG Qiang, WANG Yi-min

2005, 23(1):  86-89. 

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This paper discusses the maximum entropy spectrum analysis of runoff time series, compares it with traditional spectrum analysis, and presents the high-resolution character of the maximum entropy spectrum and the prospect of its application in hydrology.The analysis and calculation of the annual runoff time series at Lanzhou station on the upper reaches of the Yellow River, prove that the significant periods of the annual runoff are 11, 6.25 and 3 years at Lanzhou station.The conclusion illustrates the feasibility of this method and provides scientific data for runoff forecasting.

Wave-Based Study for Cable Tension Measurement of Cable-Stayed Bridge

WANG Jun, WANG Feng-quan, ZHOU Xing-de

2005, 23(1):  90-93. 

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The basic theory of cable tension measurement and its examination technology by the method of vibration wave are introduced in this paper.In practical measurement, it has found that stress wave excited by the sinusoid impulsion contains too much noise, so the time difference between two signals could hardly be discerned.According to the theory that the maximum modular values of wavelet transform signals and random noises have different spreading characteristics, wavelet sym3 which has approximately symmetric character is adopted to decompose the noise signal, and each wavelet transform coefficient is conducted by different soft threshold.The noise-extracted signal which is reconstructed by the revised wavelet coefficient could clearly reflect the time difference between incidence wave and reflection wave.

A Study on the Void Distribution of Porous Materials Being Dried

GE Shi-fu, SHI Ming-heng

2005, 23(1):  94-98. 

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Basing on the analysis of micro-structure and the experimental data of equilibrium moisture content of the porous construction materials, this paper studies the relationship between the equilibrium moisture content and the void distribution of porous materials.The results show that the void distribution obeys log arithmic normal function.According to this, the relation between the vapor pressure P(r)/P_H and the moisture content of the porous materials in the falling rate drying period is obtained.The calculation result approximately agrees with the experimental data with only 3.01% root mean square error.In addition, the effects of the void distribution parameters μ, σ, the temperature and the moisture content on the vapor pressure P(r)/P_H of the porous materials in the falling rate drying period are analyzed.The results can be used to study the heat and mass transfer of porous materials during the falling rate drying period.

Analyzing Rotor Rotating Error Using Fractional Brownian Motion

WANG Kai, LI Yan, ZHENG Jian-ming

2005, 23(1):  99-102. 

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According to variance changing laws of a precise rotor radial rotating error motion, it can be proved that the rotor's motion track is characterized by fractional Brownian motion.Then non-dimension fractal box counting dimension has been adopted to describe the rotor's radial rotating error motion, and it also be taken as a parameter to estimate the complexity of axes motion track.At last, Hurst exponent was adopted to describe the stability of axes rotating motion.

An Approximate Expression of the Effective Permittivity in the Inhomogeneous Difference Unit Grid

BAO Xiu-long, LI Zheng-fan, SUN Xiao-wei

2005, 23(1):  103-107. 

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By applying the circuit concept of series-parallel connection of capacitance, the approximate formulae of effective permittivities along x, y, z axes for various inhomogeneous cell grids are obtained.These formulae are combined with the FDTD scheme and MRTD method of the arbitrary spatial grid to calculate the resonant frequency of resonance cavity under the condition of numerical stability.This method can save computing time and memory than the conventional FDTD method.These effective permittivities formulae are also applied in the difference method for other electromagnetic problems.

Joint Source-Channel Coding/Modulation Based on NN

YIN Wei-wei, LI Rong-wei, WU Le-nan

2005, 23(1):  108-110. 

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A new JSCCM scheme based on a probabilistic neural network is proposed.The complexity and delay in this system is less than the traditional one and it is more robust against channel errors.Simulation results demonstrate that the performance of the JSCCM is far better than that of the tandem coding modulation system.