Table of Content

30 November 2006, Volume 24 Issue 6

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Articles

A Simple Formula for ICI Caused by Single Frequency Offset in Wireless OFDM System

SHU Feng, CHENG Shi-xin, CHEN Ming, YOU Xiao-hu

2006, 24(6):  551-554. 

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Normalized interchannel interference (ICI) power (NIP) caused by normalized single frequency offset (NSFO) has been derived to be one third of the square of NSFO by mathematical skills under the condition that each path has the same SFO.Compared with Moose's and Feng's bounds, this simple formula provides both easy and precise calculation for NIP. Simulation indicated that this identity holds when|NSFO|≤0.2 and N_c≤4 where N_c is the total number of subcarriers. Finally, this simple formula is applied in derving NIP expression resulting from Doppler spread in a wireless channel.

An Improved Alignment Method and Its Application to the Localization of Facial Features

JI Zhen-hai, ZOU Cai-rong, ZHAO Li

2006, 24(6):  555-559. 

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This paper presents a new method to align the facial feature points, which is developed from the generalized procrustes analysis, and improved by adding nonlinear information of facial points and using the active shape model and the kernel trick.Experiments show that the improved method has better performances in obtaining more detailed modes of face shape and better accuracy in searching unknown target image points.Meanwhile less time is spent for the search.

A Novel Time-Domain Equalization Algorithm for Narrow Band Interference Suppression

ZHANG Yu-heng, WU Qi-hui, WANG Jin-long

2006, 24(6):  560-564. 

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From the steepest descent analysis of Wiener filtering, a new algorithm termed AJ (anti-jamming) LMS equalization is proposed, which adaptively adjusts the weight factors of the equalizer based on the estimated channel. Results of analysis and simulation show that performance of AJLMS is better than the LMS algorithm in terms of narrow band interference (NBI) suppression although computation complexity is increased to some extent.

Time-Varying Channel Estimation and Pilot Tone Placement for MIMO OFDM Systems

HU Die, YANG LÜ-xi

2006, 24(6):  565-568. 

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Time-varying channel estimation for MIMO OFDM systems is challenging.Based on piecewise linear model, this paper proposes an estimation method that first estimates the slope of linear variant and the channel impulse response at the middle time of the current OFDM symbol using pilot sequences, and then estimates the whole channel impulse response through the estimated parameters.Along with the estimation scheme, pilot tone placement is studied.It is better to group pilot tones together into clumps that are equispaced in the frequency domain.Simulation results show effectiveness of the proposed scheme and demonstrate superiority of using the equispaced-grouped pilot sequences.

Transmission Characteristics Analysis for Trapezoidal-Ridge Metal Waveguide Using 2-D FDFD

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

2006, 24(6):  569-572. 

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Transmission characteristics of trapezoidal-ridge metal waveguide are analyzed using 2-D FDFD.The general 2-D FDFD equations in the Cartesian coordinate system and difference equations for the trapezoidal bevel edge of the waveguide are presented.Transmission characteristics of single and double trapezoidal-ridge waveguides are then analyzed using these equations.Computed results are in good agreement with the previously published ones, showing validity of the method.

Generalized PDA Algorithm and Iterative Detection for MIMO System

XIAO Hai-yong, BI Guang-guo, JIN Xiu-feng

2006, 24(6):  573-576. 

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By studying the existing probabilistic data association (PDA) algorithm for MIMO system, this paper proposed a generalized probabilistic data association (GPDA) algorithm for system with the number of receiving antennas less than transmitting antennas and more than half of transmitting antennas.Factors affecting the system performance are discussed, and the GPDA algorithm is revised to be suitable for iterative detection.Simulation results indicate that the GPDA method can effectively improve the detection performance, and the iterative detection can further improve the performance.

Sidegating Effect of GaAs MESFET with Planar Selective Ion Implantation

LU Sheng-li, DING Yong, SHI Long-xing

2006, 24(6):  577-581. 

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This letter studies the sidegating effect of GaAs MESFET under the same processing technology of planar selective ion implantation.In the experiments, characteristics of the sidegating effect were analyzed.The observations strongly depend upon the peculiarities of channel-substrate (C-S) junction and impact ionization of traps-EL² under high field.The obtained results are of particular pertinence to the design of low-noise and high integrated GaAs IC' s.

Topological Visualization Method for DT-MRI Dataset

BAI Heng, WANG Shi-jie, LUO Li-min

2006, 24(6):  582-587. 

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A topological visualization method for DT-MRI dataset is introduced.The 3D diffusion tensor is projected onto a two-dimensional slice plane, and the in-plane diffusion is considered.By topology analysis, the topological structure of the corresponding diffusion tensor field is extracted.Topological features of cerebral tissue such as corpus callosum and thalamencephalon, detected in the horizontal, coronal and sagittal plane, indicate that the topological method provides an accurate and synthetic depiction of the underlying framework.Compared with simple fiber tracking, the topology-based visualization represents complex structure by simple points and lines, resulting in a clearer description.Connectivity of field can also be dramatically enhanced.

Modularization of Metabolic Network Based on Graph Clustering Algorithm

HOU Jing, SONG An-ping, WANG Zhuo, ZHANG Wu, LI Yuan-yuan, LI Yi-xue

2006, 24(6):  588-592. 

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This paper proposes a new methodology to disclose the functional information of complex metabolic network based on graph clustering algorithms and modular structure comparison, and indicates photosynthesis evolution in view of systems biology.In addition, two graph clustering algorithms, the Markov clustering and simulated annealing clustering, are introduced.The corresponding clustering results of chloroplast and cyanobacteria are presented.A similarity measure is defined to find the conservative functional module between chloroplast and cyanobacteria, and the overall structure of modules is compared with the counterparts in different species.

Delegation-by-Certificate Based and ID-Based Proxy Signature Schemes

WANG Xiao-feng, ZHANG Jing, WANG Shang-ping, ZHANG Ya-ling

2006, 24(6):  593-597. 

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A delegation-by-certificate proxy signature scheme and an ID-based proxy signature scheme are proposed under assumption of a factorization problem.The new schemes have such desirable features as strong un-forgeability and nonrepudiation, distinguishability, verifiability, identity confirmation of original and proxy signers, and revocability of the proxy signature delegation.The ID-based proxy signature scheme overcomes the limitation of some existing schemes that do not include ID information of signer and proxy signers.The proposed schemes allow online signature of the original signer, and are simple and efficient, and capable of resisting existing attacks.These schemes can be used in distributed computing, mobile agent, e-commerce and e-government systems.

Temporal Logic Semantics Model and Its Implementation Using PVS

XU Qing-guo, MIAO Huai-kou

2006, 24(6):  598-603. 

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As a specification language, temporal logic is powerful enough in expressing the properties for program.In order to prove the theorem that expresses the property using temporal logic formula in a prototype verification system (PVS), this paper establishes a semantics model for temporal logic as well as the semantics interpretation.As an example, a program for solving the square root for an integer is investigated.Some properties of this program are specified in temporal logic formulas.An interface for verifying program by PVS is provided.

Backstepping Control of Synchronization for Biomathematical Model of Muscular Blood Vessel

GONG Chong-ying, LI Yi-min, SUN Xi-hao

2006, 24(6):  604-607. 

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In this paper, a method of vasospasm synchronization is proposed using a Backstepping technique.Vasospasm is a biomathematical model of muscular vessel arising in diseases such as miocardial infarction.A suitable controller is designed by selecting a series of Lyapunov functions, making synchronization error between the master and slave systems approach an equilibrium point.Global stability and synchronization can be achieved.In theory, a vessel in spasticity would synchronize with the normal vessel.Simulation results are presented to show the effectiveness of the proposed approach.

Analysis of Terrain Information Using Elevation Matching Based on Entropy

LI Xiong-wei, LIU Jian-ye, KANG Guo-hua

2006, 24(6):  608-612. 

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Terrain unaided factor and terrain information entropy are defined for the terrain contour matching (TERCOM) elevation-aided navigation system.Statistical characteristics of terrain information entropy are described, and the entropy relation between terrains of different sizes introduced.Mathematical models of various terrain parameters are presented, including SNR, roughness, slope, correlative length and terrain information entropy, etc.Based on a digital elevation model (DEM), qualitative and quantitative analyses are given with graphs of terrain navigation performance and suitability.By means of statistical analyses and threshold value settings, a suitable terrain is selected with better navigation performance.From the results a terrain database can be established for navigation, terrain suitability evaluation and flight course planning.

Application of Nonlinear Dynamic Inversion Control in Flight Control of Hypersonic Vehicle

LIU Yan-bin, LU Yu-ping

2006, 24(6):  613-617. 

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Unlike conventional aircrafts, hypersonic vehicles require that the propulsion system be integrated into the airframe.As a result, the hypersonic vehicle model is highly nonlinear and possesses significant input-output coupling. In order to provide satisfactory nonlinear decoupling ability and maintain good longitudinal stability, we apply nonlinear dynamic inversion control in designing the flight control system of the hypersonic vehicle.Simulation studies show that the approach can meet the control system requirements.

Attitude Determination of Miniature Air Vehicle Based on MEMS-INS

LI Rong-bing, LIU Jian-ye, DUAN Fang, NIU Xin-yuan

2006, 24(6):  618-622. 

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A prototype of attitude determination for miniature air vehicles (MAV) is constructed.The performance of MEMS inertial sensors and the bias models with respect to temperature are analyzed.A nine-position calibration method for non-orthogonal and alignment error is present.The noise of MEMS inertial sensors is analyzed using correlation theory.Based on micro inertial navigation system and the noise characteristic of MEMS inertial sensors, attitude integrated algorithm adapt to real application in MAV is constructed.The performance of horizontal attitude is tested on rotating floor.Bias stability of gyro and accelerometer is 0.036 (°) s and 0.01 m/s², and the RMS errors of roll and pitch are 0.33ånd 0.28°respectively.Test results indicate that error compensation on sensors and system has an integrated effect with attitude error reduced by 50%.MEMS-INS-based attitude determination can meet the need of autonomous attitude stabilization of MAV.

Application of Nonresonant Photoacoustic Cell in Fire Detection

JIANG Ya-long, CHEN Tao, YUAN Hong-yong, ZHANG Yong-ming, ZHU Yu-quan, WANG Jin-jun

2006, 24(6):  623-626. 

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The photoacoustic technology has great advantage in fire detection.Design of photoacoustic cell is a key factor affecting the measurement results.This paper introduces application of nonresonant photoacoustic cell in fire detection. The environmental disturbance has less influence on the measurement results due to low modulation frequency.Small photoacoustic cells (approx.1 cm³) can reduce the dimension of the whole detection system.Changes in carbon monoxide concentration in a smolding cotton fire and flaming spirits fire are measured.The results indicate that nonresonant photoacoustic cell has a better performance in fire detection.

Correction of Anamorphic Vision Image with Perspective Lines

YANG Yong-yue, DENG Shan-xi, WANG Xun-si

2006, 24(6):  627-632. 

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Anamorphic vision images are corrected with perspective model of lines.An approximate line passing through the center is approached by anamorphic curves.Intersection of two different approximate lines is regarded as the image center.Distortion is analyzed with a radial anamorphic model.The anamorphic coefficient is combined with the vision process to correct an anamorphic image for the final calibration of the liner model.

Analysis of Railway Catenary System Based on Markov Theory

WAN Yi, DENG Bin, LI Hui-jie, TIAN Zhi-jun, KE Jian

2006, 24(6):  633-636. 

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Reliability of the railway catenary system is a key to the safety of trains.In this paper, a mathematical model is established using the Markov theory and statistics based on the repairable characteristics of catenary.Availability, reliability and the mean failure time are derived.Reliability of the Bao-Cheng Railroad is analyzed and forecasted with the model.It is compared with the reliability of overseas catenary.Effective measures are proposed to improve catenary reliability.This study provides a theoretical basis and a new method for reliability design, maintenance and management of the railway system.

Image Analysis for Mandibular Molar and Post-Core Prosthesis

WANG Wei, LIU Gen-di, DONG E-liang, HE Xiao-yuan

2006, 24(6):  637-641. 

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A normal mandibular molar and its post-core prosthesis were embedded in periodontal support simulated by composite resin and formed a embedded block with size 18 mm×16 mm×22 mm.By digital optical test, their displacement and strain were obtained under a vertical applied force.Meanwhile, mechanical characteristic were analyzed.Based on the study, the following results are obtained. (1) With loads at the same level, the strain of postcore prosthesis is higher than the strain of original molar;therefore, high occlusion loads should be avoided. (2) By postcore prosthesis, advantage of inherent geometry features of left root can be taken, which is a gradual process of dispersing occlusion loads. (3) It is proved that the digital optical method is an alternative means in stomatology.

Ejector in Compression/Ejection Hybrid Refrigerator: Design and Performances

LIU Jing-hui, CHEN Jiang-ping, CHEN Zhi-jiu

2006, 24(6):  642-646. 

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This paper presents a method to determine diameter of mixing chamber in the ejector of a vapor compression/ejection hybrid refrigeration system (VCEHRS), and discusses its performances that vary with the working condition.The results show that an optimum diameter exists, corresponding to the maximum COP of VCEHRS.The performance deviates from the designing target when the working condition varies.The variation of refrigeration capacity of VCEHRS is smaller than that of traditional refrigeration systems.

Research Notes

Design of Low-Density Parity-Check Codes for Digital Amplitude Modulation Broadcasting System

WANG Jia-qing, YU Xiao-yan, WU Le-nan

2006, 24(6):  647-649. 

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The recently proposed extrinsic information transfer (EXIT) chart is a powerful yet simple method for optimizing irregular low-density parity-check (LDPC) codes.In this paper, the technique is applied to a digital amplitude modulation broadcasting (DAMB) system with satisfactory results.Simulation results show that optimized LDPC codes outperform turbo codes in various broadcast channels.This may provide references in developing DAMB systems.

A New Method for Single Observer Passive Location Based on Slow Moving Platform

GAO Wei, ZHOU Xi-lang, WU Lin-sheng, ZHANG Wei-jiong

2006, 24(6):  650-652. 

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This paper develops a method to estimate position of emitter based on distribution characteristics of bearing measurement errors.Having obtained an initial position with a least-square method, a more precise result can be worked out from information contained in the bearing measurements.Better results are attainable by using this method without la rge-scale matrix operations.Simulation results show its effectiveness.

FDTD Analysis of Symmetrical FSS Based on Even-Odd Mode

ZHOU Yong-gang, XU Jin-ping

2006, 24(6):  653-655. 

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In this paper, periodic boundary conditions in the time-domain excited by single frequency odd mode and even mode incidence are derived.The scattered field of a 2-D FSS formed by infinite-periodic strip grating with a dielectric support and excited by a single-frequency obliquely incident plane wave is simulated with FDTD based on the odd-andeven mode technique.Compared with the dual-plane wave method, perfect agreement between numerical results is achieved.At the same time, the required memory size is reduced by 50% and the computation efficiency is improved by 100%.Validity and applications of the proposed method is demonstrated.

Call Admission Control Using Quality Degradation Strategy in Wireless Multimedia Networks

WU Yue, LI Jian-hua, BI Guang-guo

2006, 24(6):  656-660. 

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This paper presents a call admission control scheme using quality degradation strategy to provide QoS in wireless multimedia networks.The proposed scheme is adaptive to bandwidth of multimedia call, which keeps the total call blocking probability and dropping probability for real time traffics lower than those in the fixed reservation scheme at a price of slight degradation of multimedia calls.Different policies are enforced for three different degradation levels to prevent fast bandwidth loss especially under heavy load conditions.Simulation results show that the proposed call admission control scheme outperforms other known schemes in terms of smaller CBP and CDP for real-time traffic and slower degradation in heavy load network traffics.