Table of Content

31 March 2005, Volume 23 Issue 2

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Articles

The Application of Discrete Measurement Event in Hybrid System State Estimation

MO Yi-wei, XIAO De-yun

2005, 23(2):  111-116. 

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By defining the discrete measurement event (DME), extra quantitative values can be extracted from quantized qualitative measurement signals.Together with continuous quantitative signals, this quantitative information acquired from quantized qualitative signals is used in hybrid state estimation to improve state estimation results and acquire better estimation performance.The application scheme of these extra quantitative values in hybrid state estimation is discussed in this paper.Moreover, its design steps and the method of implementation are given.The feasibility of the proposed state estimation approach based on DMEs is validated by simulation experiments.Simulation results show that DME can improve the speed and precision of state estimation in hybrid system.

A Novel Chip Equalization Algorithm for Sparse Channels

WU Qi-hui, ZHAO Chun-ming, GAO Zhan

2005, 23(2):  117-121. 

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High-speed packet transmission is an important characteristic in the 3^rd generation mobile communication system.The chip equalization technique is one of the important methods that enhance the performance of the high-speed packet transmission in the low spreading factor.For sparse channels, a novel RLS (SMRLS) algorithm is presented.Theoretical analysis and computer simulations show that the performance of the SMRLS is superior to conventional Rake.The new algorithm maintains the steady-state MSE of the conventional MRLS approximately, while the convergence speed is increased and computation complexity is reduced greatly.It proves to be of great value in practical application.

The Application of PBSV-DDM in EM Scattering Analysis of Electrically Large 2-D Objects

AN Xiang, LÜ Zhi-qing, HONG Wei, CUI Tie-jun, YIN Xiao-xing

2005, 23(2):  122-125. 

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A new highly efficient domain decomposition method based on the partial basic solution vectors (PBSV-DDM) is presented for solving arbitrary electrically large 2D electromagnetic scattering problems. Different from the traditional domain decomposition method (DDM) by which one needs to solve matrix equations in each sub-domain during every iteration till convergence, which is considerably inefficient and time-consuming, the matrix equations in the new PBSV-DDM algorithm could be solved for a set of standard orthogonal excitation vectors to get the partial basic solutions.Then the solution in each sub-domain is obtained only by a simple vector summation operation in every iteration procedure.Obviously, the computational efficiency would be greatly improved.The validity and computational efficiency of PBSV-DDM have been verified by numerical examples.

Image Restoration Based on the Modified Paik-Hopfield Neural Network

HAN Yu-bing, WU Le-nan

2005, 23(2):  126-130. 

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In this paper, a modified Paik-Hopfield neural network model based on the new state updating rule is proposed for restoring a degraded image.The convergence, the residual error and the energy change of the full parallel mode are thoroughly studied.An improved iteration algorithm based on the idea of "from coarse to fine" and the difference estimation between two adjacent layers is also presented.Experimental results demonstrate that this method can approximate the minimum of the energy infinitely and greatly improve the speed of convergence as well as the precision.

The Design and Implementation of the Authentication Service in WLAN Based on ACE

LI Jing, CAO Xiu-ying

2005, 23(2):  131-135. 

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Describes the authentication service in the IEEE802.11 MAC specifications and the concurrent programming mode are briefly described.The design and implementation plan of the authentication service in WLAN based on ACE is also presented.

The FDTD Analysis of the Nonlinear Lumped Element

CAI Peng, YANG Xue-xia, XU De-ming

2005, 23(2):  136-139. 

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Two kinds of nonlinear lumped elements are analyzed by the FDTD algorithm.The improved nonlinear lumped network (INL²N) -FDTD method has been used to analyze the Schottky diode in more than one FDTD grid cells.The Gunn diode has been analyzed by an effective set of FDTD iterative formulas.The analysis results are in good agreement with the relevant literature and the results of the SPICE.

A Study on Low Complexity PCGC Decoding Algorithms

LI Jin, XU Xiao-dong, JIANG Ming, YOU Xiao-hu

2005, 23(2):  140-143. 

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The parallel concatenated gallager code (PCGC), a new kind of channel code which concatenates the low density parity check (LDPC) code in parallel, can be decoded in the two-layer iterative style.The PCGC decoder has good performance, but its high computation complexity interferes with its hardware implement.In this paper two kinds of low complexity PCGC iterative decoding algorithms, and the simulation results prove that the algorithms have excellent performance are proposed.

Design of a Disturbance Reduction Controller for a Class of Nonlinear Systems with Multiple State and Input Delays

WANG Zhan-shan, ZHANG Hua-guang

2005, 23(2):  144-148. 

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To cope with the unmeasurable external disturbance having known waveform but unknown magnitudes, a disturbance compensator is designed for a class of nonlinear systems with multiple state and input time-variant delays.When the unbounded disturbance enters the time-delay systems, the systems state variables will go out of control.Thus it is necessary to design a reduction controller to compensate or minimize the effects of the disturbance.In order to obtain the estimation of state and disturbance, an augmented system is constructed by the nonlinear system and the disturbance system, and a time-delay composite state observer is designed to give the estimation of state and disturbance.Hence, the disturbance reduction controller is derived and the systems state variables are kept in control.An illustrative example shows the effectiveness of the proposed methods.

A Study of the Timing Recovery Method for OFDM on the Digital AM Broadcasting System

RUI Hua, XU Da-zhuan, ZHU Qiu-ming

2005, 23(2):  149-154. 

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OFDM is an effective modulation technique for high-rate and high-speed transmission over the frequency selective fading channel.However, the OFDM system can be extremely sensitive and vulnerable to timing synchronization errors.In this paper, a low-complexity two-stage timing recovery scheme is proposed. The timing recovery process can be divided into symbol synchronization and sample clock synchronization.In the former process, an improved ML algorithm is proposed.Its performance can approach the optimal ML algorithm without estimating SNR and therefore can have lower complexity.In the latter process, an simple synchronization algorithm is proposed using scatter pilots to estimate sample clock phase errors, and a low pass loo p filter is used to track the symbol timing drift caused by sample clock frequency offset.Simulations are carried out on DAMB channels, and the results indicate that our proposed scheme can achieved good performance and are robust to multipath fading channels.Its low complexity enables the scheme to operate easily run on the DSP chip.

An Equalization Multi-thread Scheme to Realize IEEE802.11 MAC Protocol

CHEN Li-quan, HU Ai-qun, HU Jun, LI Wei-zheng

2005, 23(2):  155-159. 

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There are 22 models in the finite state machine of IEEE 802.11 MAC protocol.When a single thread or multi-thread schemes are used to realize this MAC protocol, the equalization between efficiency and realization is not easily achieved.The proposed equalization multi-thread scheme can realize the balance between system efficiency and feasibility.The results from simulations also support this point.

A Signal Processing Method for the Coriolis Mass Flowmeter Based on a Normalized Lattice Notch Filter

NI Wei, XU Ke-jun

2005, 23(2):  160-164. 

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An adaptive normalized notch filter is applied to filter the sensor output signals of a Coriolis mass flowmeter and calculate its frequency.An adaptive line enhancer based on the above-mentioned notch filter extracts the required signals from the noisy data.The sliding Goertzel algorithm is used to calculate the real time phase difference between two signals of this kind.With the frequency and phase difference obtained, the time interval of the two signals and the mass flowrate are derived.The simulation results show that the algorithms studied in this paper are efficient.

The Design of a Payment Gateway Emulator for the TPC-W Benchmark and Its Performance Analysis

LUO Zhen, LI Sheng-li, XIE Xia

2005, 23(2):  165-168. 

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The architecture of TPC-W benchmark is introduced briefly in this paper, which followed by description of the schema of payment gateway emulator (PGE) and its interactive authentication process with the server under test (SUT).It compares the performance of web server with and without the payment gateway emulator and then analyzes its performance with the change of test mode and database size.The result shows that TPC-W benchmark can simulate the true behavior web server so as to evaluate server's performance exactly with different workload by changing the parameters within the range of possibilities and find the performance bottleneck.

The Effect of MOSFET Output Impedance on Linearity in the CMOS Gilbert Mixer

TANG Shou-long, LUO Lan, LU Sheng-li

2005, 23(2):  169-173. 

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The nonlinearity behavior of the CMOS Gilbert mixer is investigated.The impact of MOSFET output impedance on distortion is studied in depth.The mixer nonlinear model and optimal drain-to-source voltage bias are presented in this paper.The rate of error between the analytical predictions and the Cadence SpectreRF circuit simulation results is less than 10%.

The Recursive Constant Modulus Algorithm for Fast Moving-Targets Tracking

GUO Yan, LI Ning, LI Li, FANG Da-gang, PEI Yu-ling

2005, 23(2):  174-177. 

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A new blind beamforming algorithm to fast track several movable users was proposed in this paper. Instead of forming independent beams at different times by the conventional method, the information of the users' DOA obtained from the previous beamforming is made full use of.It can greatly speed up the subsequent beamforming and lead to enormous saving in the required real time computations.Therefore, the new beamforming algorithm could keep up with the moving targets more quickly, which is of great importance in real communication systems.Simulation results confirm our ideas.

An Efficient Diagnosis Algorithm for the Test of Embedded SRAM

REN Ai-ling, LING Ming, WU Guang-lin, LI Rui

2005, 23(2):  178-182. 

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This paper puts forward an self-diagnosis bit-oriented algorithm(MARCH-TB +), according to the testing algorithms,we use a shared built-in-self-test structure(parallel structure) to test and diagnose embedded SRAM(2k×1).The experimental results show that the proposed testing algorithm has high fault coverage, strong diagnostic ability and requires less testing time.

The Design of Low Distortion High Speed Sample/Hold Circuit

XIA Wei-yi, WU Jian-hui

2005, 23(2):  183-186. 

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A low distortion, high speed switched capacitor sample and hold circuit has been designed.A novel bootstrapped switch is used to degrade the nonlinearity and the method to decrease the settling time of the amplifier is proposed.The simulation shows that it achieves more than 70 dB linearity at a sampling rate of 40 MHz.

ANN-CE: An Improved Neural Network Method for Predicting DNA Binding Sites

XU Dong, WANG Yi-fei

2005, 23(2):  187-191. 

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The neural network technology has achieved great success in the field of bio-sequence analysis.But a neural network based on MSSE is not the final solution to the problem of predicting DNA binding sites.In this paper, An improved neural network method, ANN-CE, to predict DNA binding sites is presented.It is a three layered back-propagation neural network in which the error function is a cross entropy function.The result shows that the predicted sensitivity and specificity of ANN-CE increased by 11.40% and 11.91% respectively compared with the back-propagation neural network based on MSSE with the same architecture.

A Study on the Theory and Experiment of Measuring the Residual Stresses Distribution in Thick Pre-stretched Aluminum Plate 7050T7451

WANG Shu-hong, ZUO Dun-wen, LI Xiang-feng, WANG Min

2005, 23(2):  192-195. 

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According to the characteristics of the thick pre-stretched aluminum alloy plate, a new method of measuring the residual stresses in thick plate is deduced by the elastic mechanical theory.The residual stresses distribution along the thick direction of plate 7050T7451 is measured by the new method, and the results of measurement are analyzed.It is shown that the new method deduced in this paper is simple and accurate, and is very useful in engineering.

A Research on Aero-Engine Maintenance Level Prediction Based on Statistical-Rough Sets Theory

LIANG Jian, ZUO Hong-fu, CHANG Ji-bai, ZHAO Hong-hua, ZHOU Zuo-cheng

2005, 23(2):  196-199. 

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The airlines pay close attention to maintenance cost for efficiency improvement and consumption reduction.In this paper, basing on the theory of rough set, the problem of how to determine proper shop visit workscope before the aero-engine being removed is discussed.The key point is to obtain related rules between the on-conditional parameters and the performance of engine units.The uniformity of rough set and statistical methods are employed to find out the significance of each attributes by its knowledge entropy.The rules can be generated by determining the significant degree of each attribute.According to the experimental results, the proposed new method can improve the prediction accuracy for drawing up shop visit workscope.The method has been partly adopted by airlines, and it is proved to be helpful to reduce the costs of airlines.

The Precision Measurement for Large Diameters Based on Multi-roller Method

JIN Shi-qun, DING Xiao-mu, FEI Ye-tai, YU Xiao-fen, CHEN Xiao-huai

2005, 23(2):  200-203. 

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A multi-roller and multi-sensor measurement solution based on the analysis on the intrinsic limitations of the single-roller method is proposed to measure the large diameters accurately.In the measurement system designed, the multiple rollers and data fusion technology are used to eliminate the sliding signals, as well as the separating and correcting the measurement errors aroused by the thermal-deformation and pressure deformation to improve the measurement accuracy of the system observably.In this paper, the measurement principle and system of the roller method are introduced and the measurement errors are analyzed.The experimental results show that the measurement accuracy of designed system exceeds 5 μm/m.

A Robust Design Based on the Dissipation Theory for the Linear-Course Trajectory Control of Underactuated Ships

LI Tie-shan, YANG Yan-sheng

2005, 23(2):  204-208. 

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The idea of strict dissipation is introduced into the straight-line tracking control system for underactuated ships.The robust dissipative control for the system with bounded exogenous disturbances is studied. Based on the dissipative inequality, a globally robust state feedback controller is developed so that the resulting closed-loop system is both strictly dissipative and asymptotically stable.Furthermore, the proposed algorithm is able to enable an underactuated ship to be globally and ultimately stabilized on a prescribed straight line under external disturbances.Numerical simulation results are presented to validate the effectiveness and transient performance of the proposed controller.

The Magnetic Properties and Bioactivity of Ferromagnetic Glass-Ceramics in the System Fe₂O₃-CaO-SiO₂

YANG Jia-kuan, YANG Shu-hua, HE Gui-li, XIAO Bo

2005, 23(2):  209-213. 

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Bioactive and ferromagnetic glass-ceramics are useful as thermoseeds for hyperthermia treatment of cancer.The ferromagnetic glass-ceramics in the system FeO-Fe₂O₃-CaO-SiO₂ have been prepared with the addition of a small amount of B₂O₃ and P₂O₅.The microstructure analysis, XRD, magnetometer test and soaking in simulated body fluid have been carried out in the study of the ferromagnetic glass-ceramics.The results show that the glass-ceramics have two important properties:magnetic properties and bioactivity.Better microstructure with the main crystal magnetite and secondary crystal wollastonite evenly distributed can be obtained through the optimal heat treatment carried out directly under 1 000℃ for two hours without nucleation, and the magnetic properties of the ferro-magnetic glass-ceramics thus made are the best in quality.With the increase of Fe content, the magnetic properties tend to increase.On the other hand, Fe can suppress the formation of the apatite on the surface of glass-ceramics.It is, therefore, necessary to carry out in-depth research to find the way to balance the effects of Fe.

A Research on Multicast Access Control Based on Policy

LIU Li, LI Jin-sheng, HONG Pei-lin, ZHU Wen-tao

2005, 23(2):  214-217. 

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The current multicast model provides no access control mechanism.Any host can send data directly to a multicast address or join a multicast group to become a member.After analyzing the different types of multicast participants and the requirements of access control, a multicast access control system based on policy ACL is put forword.And after the model of this system is given, the process of requesting, replying and ACL configuration of the host access is also elucidated in this paper.

Research Notes

The Proof of the Equivalence of the Message Passing Algorithm to the Belief Propagation Algorithm

DU Peng, BI Guang-guo

2005, 23(2):  218-220. 

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The details of three important LDPC decoding algorithms, including hard-decision based algorithms, message passing algorithms and the belief propagation algorithm are presented in this paper.It proves the equivalence of the message passing algorithm to belief propagation algorithm.The results show that the message passing algorithm is a realization of the belief propagation algorithm in the logarithm domain.