Table of Content

31 March 2006, Volume 24 Issue 2

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Articles

Serial Circuit Architecture for Power-Sum in GF(2^m)

YUAN Dan-shou, RONG Meng-tian, LI Xin-tian

2006, 24(2):  111-114. 

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An iterative algorithm for computing power-sum in GF (2^m) is proposed using polynomial basis.During each iteration step, one bit-vector polynomial multiplication and reduction modulo of irreducible polynomial are computed. Based on this algorithm, a new serial power-sum circuit architecture is designed, with area complexity of O(m), and throughput of one result per m clock cycle.Compared with existing power-sum architectures, the proposed method has small area complexity, thus well is suited to VLSI design of applications with small chip area requirements.The powersum architecture can be used to compute exponentiations and squares.

Data Hiding in Text File Using TeX and Extraction of Hidden Data from Document Image

CHEN Chao, WANG Shuo-zhong, ZHANG Xin-peng

2006, 24(2):  115-119. 

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A steganographic technique using pdf files to carry secret data is proposed.Data are embedded into the control sequences in a TeX source file to slightly modify inter-word spaces in the text.Appropriate coding schemes may be applied.The coded TeX file is then compiled and converted to generate a stego-pdf file, which is convenient to be disseminated over the Internet.In reception, jpg images are obtained from the pdf document, and the hidden data are extracted by detecting the spaces between words.Data security is determined by the ability of reliably detecting small difference in space widths, size of the document file in terms of the amount of data to be embedded, and the encryption and coding techniques used.

Federal Filtering Algorithm in SINS/Beidou/STAR Integrated Navigation System

HUA Bing, LIU Jian-ye, XIONG Zhi, ZHU Yan-hua

2006, 24(2):  120-124. 

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Beidou satellite navigation location system is China's first generation satellite navigation system.The star sensor is a high precision attitude-measuring instrument.On the basis of non-feedback federal filtering, Beidou navigation lo cation system and the star sensor are used together in an integrated navigation system in order to set up the SINS/Beidou/star integrated navigation system.From the characteristics of Beidou and the star sensor, causes of delay and asynchronous problem in the instrumentation are analyzed, and a solution is proposed.Simulation shows that this integrated navigation system has high precision and good tolerance to faults.This shows application potentials for the Beidou system in defense industries.

Reliability Description of Fault Detection and Optimization Algorithm of Sensor Location

YANG Fan, XIAO De-yun

2006, 24(2):  125-130. 

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Reliability problems in fault detection for large-scale complicated systems are studied by using a probabilistic signed directed graph (SDG) model.Influences of sensor selection and location on reliability with respect to different sensor fault probabilities are analyzed.When system faults occur, the sensors can detect the departure of variances, but the system faults may be ignored or misdiagnosed because of the sensor faults, directly affecting the fault detection reliability. With description of the probabilistic SDG model, the reliability description of fault detection is given.Optimal sensor lo cation and the corresponding algorithm are studied under restricted resources.Furthermore, a probabilistic SDG model is established for a typical 65 t/h boiler, on which the above algorithm is executed to determine an optimization scheme. Simulation experiment shows that sensor location solved in this way is effective in improving fault detection reliability.

Laser Frequency Repetition Times in Portable Aerial Target Measurement

MA Jian-wei, LI Peng, SHENG An-dong, GUO Zhi

2006, 24(2):  131-134. 

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The problem of laser frequency repetition (LFR) times in target distance measurement is studied.In analyzing flight path data, power spectral density is computed to obtain the frequency range and times of LFR using the Shannon theorem.Under the assumption of line movement with constant velocity, the flight path is built such that prediction error variance computed by the LFR times meets the specified requirements.Relation between error variance and the maximum allowed number of missing measurements is presented.It is proved both in theory and from practice that the LFR times can meet the performance specifications of laser echo rate while guaranteeing the tracking precision.

A New Character-Localization Method in Wavelet Transform Domain

ZHANG Er-hu, ZHANG Xu-jin, ZHANG Zhi-gang

2006, 24(2):  135-139. 

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Characters in an image often provide important information of the image.Extraction of characterregions enables one to quickly browse and retrieve specific images.Based on analysis of the property of characters and study of their features in the wavelet transform domain, a new method for localizing and extracting characters is proposed.By using an adaptive dynamic threshold together with information of the adjacent blocks, the rate of correct-detection may be raised.A special feature of the method is that only partial decoding is required for encoded images involving wavelets such as JPEG2000 and MPEG4. Experimental results show that the processing is fast and correct-localization rate is high.

Kernel Canonical Correlation Analysis and Application for Face Discrimination

HE Yun-hui, ZHAO Li, ZOU Cai-rong

2006, 24(2):  140-144. 

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Based on the equivalence between canonical correlation analysis (CCA) and Fisher linear discriminant analysis (FLDA), nonlinear discriminant features of face images are extracted with kernel CCA.These features are equivalent to those extracted with KFDA.Experimental results demonstrate that KCCA is similar to GDA and significantly better than FLDA.

A Stable Mobile ad hoc Network Routing Algorithm with Gray Prediction

YANG Pan-long, TIAN Chang, NI Ming-fang

2006, 24(2):  145-149. 

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Due to the highly dynamic topology and complicated network scenario, stability is a key factor in ad hoc routing protocol efficiency.In this paper, the gray theory is applied to topology state prediction in mobile wireless ad hoc network in order to improve the proactive ability of reactive routing protocol such as DSR.In the developed routing protocol, a number of factors are taken into account to avoid turbulence of routing information in network, minimize unnecessary routing overhead, rapidly find disabled links and improve stability of routing information.Simulation results show that the stable routing protocol S-DSR based on the gray prediction theory is considerably more stable and efficient than that of the original one.

A New Design Method in CMOS Analog Cell Circuit Optimization

ZHENG Wei-shan, PENG Yi-pin, ZHANG Men, WU Jian-hui

2006, 24(2):  150-153. 

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This paper proposes a new method for sizing and optimizing CMOS cell circuit.The core algorithm is the niche-based genetic algorithm.The simulated result shows that the difference between the optimized circuit's performances obtained using the proposed method and that using the simulation-based method is not obvious, while the proposed method takes much less time.

Application of Buffer Operator and Data Fusion in Target Tracking

LIU Yi-an, CHEN Song-can, ZHANG Ming-jun, MA Xiu-fang

2006, 24(2):  154-158. 

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Aiming at multi-radar target tracking in a complicated environment, this paper introduces a buffer operator of the gray system theory into a multi-radar target tracking scenario, and improves the primitive shock disturbed sequence to attenuate its randomness.Data fusion techniques are then applied to further improve tracking precision of the radar system for the random oscillatory sequence due to the buffer operator.Simulation results indicate that the method is effective and feasible.

DMVR: A Dynamic Materialized View Replacement Algorithm Based on Disk Cache Mechanism

ZHANG Bai-li, SUN Zhi-hui, ZHOU Xiao-yun, ZHANG Jing

2006, 24(2):  159-164. 

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The current dynamic materialized view selection algorithms based on disk cache can tune with the altering query requirements and possess better dynamic adaptability.However these algorithms simply refer to the memory mechanism, whithout an accurate model to take into account the cost of retrieving materialized views from disk.A dynamic materialized view replacement (DMVR) algorithm is presented, which is based on a better cost model and therefore suitable for dynamically adjusting the materialized view set.For systems with a heavy workload, that DMVR algorithm is modified to become DMVR-IDLE, which possesses and maintains a better response performance to high frequency query.Experiments have shown effectiveness of both algorithms.

Saturation Throughput and Delay Analysis of DCF in IEEE 802.11a WLAN

CHEN Yu-zhong, YANG Bing-qing, KAI Cai-hong, LIU Zheng-kai

2006, 24(2):  165-170. 

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IEEE 802.11a is a popular high-speed WLAN standard with a data rate up to 54 Mps.The basic Medium Access Control (MAC) protocol of IEEE 802.11a is the contention-based distributed coordination function.DCF includes two access mechanisms:basic access mechanism and RTS/CTS access mechanism.In this paper, an analysis and comparison of saturation throughput and access delay of these two access mechanisms in IEEE 802.11a WLAN is conducted by introducing a two-dimensional Markov model.The study reveals that, in contradiction to the situation in IEEE 802.11 WLAN, basic access mechanism is always more effective than RTS/CTS mechanism in high-speed IEEE 802.11a WLAN.

Optimization of Disposition Actuators in High Level Multiple Degree of Freedom Structures Based on Fuzzy-Genetic Algorithm

CAO Yuan, WANG Feng-quan

2006, 24(2):  171-175. 

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Optimization of actuator disposition in high level multiple degree of freedom structures is an important problem.A fuzzy algorithm, with which full use of a priori information can made, has been applied.Using this algorithm, optimization of disposition actuators is confined to a limited range, and subsequent calculations are easy and fast.The genetic algorithm has been used in the optimization, ensuring a good performance.

Gaussian Approximation of Irregular Repeat-Accumulate Codes over Mixed Gaussian/Erasure Channels

GAO Hong-feng, XU Zong-ze

2006, 24(2):  176-180. 

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Gaussian approximation models the message density in message passing decoders as Gaussian distribution.In this paper, irregular repeat accumulate (IRA) codes over the mixed white Gaussian noise/erasure channels are designed using Gaussian approximation.Recursive equations of density evolution and analytic expressions of bit error rate are derived.The analytic results not only provide a way to predict asymptotic performance of IRA codes but also help us design good IRA codes over the mixed channel.Comparison between simulation results and thresholds computed from analytic results shows that predication from the theoretical results is accurate enough.The optimized IRA codes designed for the mixed channels have better performance than that of IRA codes designed for AWGN channels when the designed erasure probability is close to the actual probability.

Quadratic Guaranteed Cost Control of a Class of Uncertain Discrete Time Delay Switched Systems

SUN Wen-an, SHEN Lian-shan, ZOU Kai-qi, LI Pi-xian

2006, 24(2):  181-186. 

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For a class of discrete-time state delay switched systems with norm-bounded time-varying parameter uncertainty, this paper addresses the problem of designing the guaranteed cost state feedback controller of quadratic stabilization under arbitrary switching laws.A condition for the existence of guaranteed cost controllers is derived.This condition can be solved easily with the MATLAB LMI toolbox.A numerical example shows the effectiveness of the method.

Approximate String Match of Special Points in Signatures and Random Forgery Elimination

QUAN Zhong-hua, HUANG De-shuang, ZHANG Guang-zheng

2006, 24(2):  187-192. 

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For on-line signature verification, extraction and matching of special points is one of the most important problems.Because the special points can be regarded as features, and used as references in segmentation and alignment. This paper proposed an approach based on approximate string match to match the sequence of special points.By calculating the edit distance between strings consisting of the types of special points, this method can quickly detect random forgeries.This can improve the speed of the system.

Energy Oriented Optimization of Allocation Strategy for On-Chip Memory

JIN Jing, PU Han-lai, LING Ming

2006, 24(2):  193-198. 

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In this paper, an allocation strategy for on-chip memory is proposed to optimize energy of memory system. With data, global variable, instruction and branch instruction, the strategy uses ECFG to get the effect of energy and capacity caused by the object relationship.By using refined knapsack arithmetic with ILP, experiment results are obtained showing that, for most applications, general energy consumption of a memory system decreases by up to 50%. Especially, when an application's capacity approaches the content of SPM content, this figure is higher than 95%.

A Novel Algorithm for Localizing Near-Field Source Using Uniform T-Shaped Linear Array

SHAN Zhi-yong, ZHOU Xi-lang, NIU Jia-xiao

2006, 24(2):  199-202. 

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A novel algorithm based on a T-shaped array for location of near-field source is presented.Under the far-field assumption of the actual near-field, equations for the bearings of far-field and the range and bearing of the near-field source are derived from two horizontal subarrays.The range and bearing of the near-field are obtained, and the bearing of another subarray determined.The azimuth and elevation of the near-field source can be determined from two bearings. The location of the near-field can then be estimated.More accurate results can be obtained by a local search.Simulation results show that the algorithm is accurate, effective and suitable for real-time applications.

Biased Sampling of Data Streams Based on Density

YANG Yi-dong, SUN Zhi-hui

2006, 24(2):  203-207. 

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As an important kind of data source, data stream has received increasing attention.Data stream management systems and data mining based on data streams have also attracted much research interest.With dynamical gridpartitioning of the data space, distribution density of data streams is approximated, and based on which a density biased sampling method is presented.To test its efficiency, the proposed sampling method is applied to clustering data streams. Experimental results show promising applicability of the approach.

An Analytical Solution to the Problem of Convection, Diffusion of Multi-phase Gases with Gas-Solid Reaction

XU Zeng-he, LI Ming-chun, TIAN Yan-wen

2006, 24(2):  208-212. 

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The gas-solid reaction aA(g)+bB(s)=cC(g)+dD(s) taking place in packed bed is studied.Convection reaction-diffusion equations for gaseous reactant and gas product are presented and solved analytically.Case computation shows that the radius of pellet affects concentration of gases considerably, and the effect can be measured by Thiele module.Since Thiele module is proportional to L² and Peclet module is proportional to L, the length of reactor itself is an important factor to affect the reaction and conversion.The overall rate of REV has greater influence on the reaction and conversion that take place in packed bed than that of convection.Therefore it is important to give the exact reaction term.

Mechanical Property Test of Polyimide/SiO₂ Film in Polyimide Regeneration Studies

DONG E-liang, KANG Xin, LIN Bao-ping, HE Xiao-yuan, WANG Feng-quan

2006, 24(2):  213-217. 

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The test method of dynamic mechanical thermal analysis (DMTA) is discussed.Measurement of mechanical properties of the polyimide/SiO₂ film using the digital speckle correlation method (DSCM) is proposed.Sub-pixel search and bilinear interpolation are used in digital image processing.As DSCM cannot be used directly in measuring large deformation, an improved multilevel DSCM is proposed.Results of Young's modulus obtained with the two methods are compared.

Research Notes

Energy Efficient Transmission for FGS Video over Markov Wireless Channel

ZHANG Ying, WU Biao, ZHANG Zhao-yang, LI Zhi-gang

2006, 24(2):  218-220. 

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In this paper, an energy efficient transmission for wireless FGS stream over a Markov fading channel is proposed.Under delay and quality constraints, the goal is to transmit an FGS stream using minimal energy by adjusting the number of bit-planes as well as slot positions for data transmission.