Table of Content

25 May 2010, Volume 38 Issue 5

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Electronics, Communication & Automation Technology

Oblique-Projection Subspace Approach to Blind Channel Estimation of MIMO-OFDM System

Sun Ji-feng Zhang Zhi-yong

2010, 38(5):  1-5.  doi:10.3969/j.issn.1000-565X.2010.05.001

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Proposed in this paper is an oblique-projection subspace approach to the blind channel estimation of MIMO-OFDM system,which,under conditions of satisfying the identification system,divides the signal-receiving space into three subspaces including the ＂past subspace＂,the ＂present subspace＂ and the ＂future subspace＂.By obliquely projecting the ＂present subspace＂ respectively onto the ＂past subspace＂ and the ＂future subspace＂,the impact of multi-path effect on the receiving system can be effectively eliminated.In addition,a method to estimate the ambiguous matrix of channel is proposed,and the singular value decomposition is adopted to improve the anti-noise ability of the algorithm.It is found that,as compared with the noise subspace approach,the proposed approach is of lower computational complexity only with slight sacrifice of estimation accuracy.Simulated results show the proposed projection approach is efficient for identifying system channel.

Elimination of Carrier Frequency Offset in Uplink OFDMA System Based on TD-LMS Algorithm

Guan Qing-yang Zhao Hong-lin Guo Qing

2010, 38(5):  6-10.  doi:10.3969/j.issn.1000-565X.2010.05.002

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A time-domain adaptive algorithm based on least mean square（TD-LMS） is proposed to eliminate the interference due to the carrier frequency offset（CFO） from different users in uplink OFDMA（Orthogonal Frequency Division Multiple Access） system.In this algorithm,the CFO in time domain is estimated and is adjusted with an estimator.Then,the residual CFO is eliminated with TD-LMS scheme in time domain.Simulated results indicate that,as compared with the algorithm based on least square,the proposed algorithm is effective in eliminating the CFO of users,with a gain of 3dB in the same simulation conditions.

Structure and Performance of Single-Carrier Frequency-Domain Equalization with Three-Dimension Signal Mapping

Zhong Yuan-hong Chen Wei Zeng Fan-xin Zhang Zhen-yu

2010, 38(5):  11-14，21.  doi:10.3969/j.issn.1000-565X.2010.05.003

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In order to reduce the symbol error rate of the conventional single-carrier frequency-domain equalization（SC-FDE） system with cyclic prefix（CP）,a structure of SC-FDE with three-dimension signal mapping is proposed,which substitutes 3D signal mapping for the traditional 2D one and converts 3D signals to 2D ones.As only the symbol mapping is changed,the conventional SC-FDE with CP can be easily substituted.Simulated results show that,as compared with the conventional SC-FDE with 2D signal mapping,the proposed structure is of significantly improved error performance and is suitable for the transmission system with low power.

Analysis of Energy Consumption of Wireless Sensor Networks

Cui Hai-xia Wei Gang Yu Yong-cong

2010, 38(5):  15-21.  doi:10.3969/j.issn.1000-565X.2010.05.004

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By considering the energy limitation of wireless sensor networks（WSNs）,an energy consumption model crossing both the physical layer and the medium access layer is proposed based on Rayleigh fading channels and wireless links.Then,a concrete energy consumption analysis is performed for IEEE802.11 DCF and slotted ALOHA protocols.Moreover,according to the variance and saturation of wireless channels,the requirements of users for channel quality and the access control mode,the energy consumption in the working process of WSNs is theore-tically analyzed.Finally,the average power consumption,the net load energy consumption rate,and the influences of transmission power and rate variance on energy consumption are discussed by simulation.It is found that the theoretical results accord well with the simulated ones,that too large or too small transmission power and rate are unprofitable to the energy consumption,and that a combined control of transmission power and rate may benefit the decrease in energy consumption.

Game-Based Spectrum Allocation in Cognitive Radio Networks

Tan Xue-zhi Liu Yu-tao Wei Shou-ming

2010, 38(5):  22-26.  doi:10.3969/j.issn.1000-565X.2010.05.005

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Based on the utility function of cognitive users,the game of licensed users in spectrum allocation is solved with the help of the oligopoly market game model.Then,based on the utility function of cognitive users and the theories of Bertrand and Cournot equilibrium,a dynamic Bertrand game algorithm is proposed for the channel pricing of licensed users.Theoretical analysis and simulation results show that the stability of Nash equilibrium solution is related to the regulative rate,that stable channel price can be obtained in a short time when the regulative rate is less than 0.020,that the Nash equilibrium point is related to the marginal cost,and that higher channel price can be obtained with a higher marginal cost.

Image Encryption Algorithm Based on Reciprocally-Disordered Diploid Chaotic Sequences Alternated in Subsection

Chen Yan-feng Li Yi-fang

2010, 38(5):  27-33.  doi:10.3969/j.issn.1000-565X.2010.05.006

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As the image encryption based on chaos is of high security and adaptability,this paper analyzes the security of the conventional image encryption algorithms based on chaotic systems and proposes a new image encryption algorithm based on diploid Logistic and Chebyshev chaotic maps.The auxiliary and the initial secret keys based on original image,as well as the reciprocally-disordered cipher sequences alternated in subsection and generated by the diploid chaotic systems,are the kernel parts of the proposed algorithm.Both the simulated and statistical results and the security analysis show that the proposed algorithm is of excellent encryption effect and high security,with a key space being up to 255×10120.

Digital Watermarking Method for Mobile Terminal Based on Image Entropy Classification

Luo Bin Gu Wei Lü Wan-li Tang Jin Li Li

2010, 38(5):  34-38.  doi:10.3969/j.issn.1000-565X.2010.05.007

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In order to protect the copyright of multimedia data of mobile terminals,improve the processing ability and enlarge the memory capacity of mobile terminals,a digital watermarking method is proposed.In this method,a novel codebook is designed based on the image entropy classification,the priority of watermarking embedding is provided for complex texture image regions to obtain high-quality watermarked image,and the conventional search algorithm is substituted with the equal-average equal-variance nearest neighbor one to accelerate the coding.Experi-mental results show that the proposed method can not only improve the codebook quality but also save the codebook training time,and that it is robust to common image processing such as JPEG compression and cropping.

Image Quality Assessment Based on Digital Watermarking in Wavelet Domain

Zhang Hua Jiang Rong-xin Chen Yao-wu

2010, 38(5):  39-45.  doi:10.3969/j.issn.1000-565X.2010.05.008

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In order to improve the precision and the watermarking invisibility of the reduced-reference image quality assessment method,a new image quality assessment method based on digital watermarking in wavelet domain is propsed.In this method,first,the texture-rich region of the original image is detected according to the characteristics of human visual system,and a watermark-embedded map is obtained.Next,a 3-level wavelet decomposition of the original image is performed.Then,a self-defined digital watermark is embedded in each wavelet coefficient block according to the watermark-embedded map,and the adaptive adjustments of quantization parameter are adopted to ensure the invisibility of watermark.Finally,the image quality is objectively assessed according to the watermark-recovering rate of the distortion image.Experimental results indicate that,as compared with the conventional image quality assessment method based on PSNR and with the reduced-reference image quality assessment（RRIQA） method,the precision,monotonicity and consistency of the proposed method are respectively 8.5% and 4.4%,5.4% and 2.2%,5.7% and 3.4% higher.

Diffused Error Concealment Algorithm Based on Human Visual System

Xiang You-jun Xie Sheng-li Zhou Zhi-heng

2010, 38(5):  46-50.  doi:10.3969/j.issn.1000-565X.2010.05.009

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In order to avoid the information loss during the compressed video transmission,an error concealment algorithm based on the diffusion equation is proposed to recover the lost information.In this algorithm,first,a distortion function considering the temporal and spatial boundary matching is presented to estimate the lost motion vectors and make an initial recovery of the lost information.Then,an anisotropy diffusion equation,which is constructed on the basis of activity-masking characteristics in human visual system,is used to make a fine recovery of the lost information.Finally,error concealments for different video sequences in discrete losing and consecutive losing cases are made by simulation.The results show that the proposed algorithm effectively reduces the blocking effect of the recovered images and achieves good visual effect,with a PSNR being averagely 3~5dB higher than that of the traditional algorithm.

Dual-Band Broadband Coupler with SIR Branches

Chu Qing-xin Yang Lin Lin Feng

2010, 38(5):  51-54,70.  doi:10.3969/j.issn.1000-565X.2010.05.010

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As the conventional dual-band coupler is of narrow operation band,this paper presents a novel design method of dual-band broadband branch-line coupler based on stepped impedance resonator（SIR）.With this method,both the location of resonate frequencies and the bandwidth of the coupler can be adjusted in the lower and upper frequency bands.A dual-band broadband 3-dB coupler operating at 2.20/5.50GHz is also designed and fabricated,which covers not only the 1.80GHz GSM band and but also the 2.45/5.25/5.80GHz WLAN bands.The measured results accord well with the simulated ones,meaning that the proposed design method is feasible.

Design of High-Efficiency Residue-to-Binary Converter for Five-Moduli Set

Chen Jian-wen Yao Ruo-he

2010, 38(5):  55-60.  doi:10.3969/j.issn.1000-565X.2010.05.011

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As the mixed radix conversion algorithm can not simultanously deal with multiple moduli,the residue-to-binary converter based on the algorithm is of large area and long delay.In order to solve this problem,a high-efficiency and parallell conversion algorithm based on the Chinese remainder theorem is proposed,and the correspon-ding circuit is designed.The proposed algorithm uses the five-moduli set {2n-1,2n,2n＋1,2n＋1-1,2n-1-1} to deal with the five moduli in parallel,eliminates all the terms whose values exceed the dynamic range,and implements the hardware by using adders as the primitive operators.Experimental results indicate that the proposed converter is 12% more compact and 14% faster than the common ones using the same 5-moduli set.

Effective Mobility Model of Polysilicon Thin-Film Transistors

Yao Ruo-he Ou Xiu-ping

2010, 38(5):  61-64.  doi:10.3969/j.issn.1000-565X.2010.05.012

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Proposed in this paper is an effective mobility model of polysilicon thin-film transistors,which simulta-neously takes into account the number of grains inside the transistor channel,the transport properties of carriers between grains and grain boundaries and the gate bias controlling the mobility degradation effect,and adapts to the polysilicon thin-film transistors from small grains to large ones in linear region.It is found that,when the grain size Lg is less than 0.4μm,the effective mobility is mainly controlled by the grain boundaries,that the effective mobility can be improved by reducing the trap density of grain boundaries,that decreasing the gate oxide thickness may enhance control of effective mobility by gate voltage,and that clear effective mobility degradation may occur at a high gate voltage.

Stability of Polymer Thin-Film Transistors Based on Poly（3-Hexylthiophene）

Liu Yu-rong Zuo Qing-yun Peng Jun-biao Huang Mei-qian

2010, 38(5):  65-70.  doi:10.3969/j.issn.1000-565X.2010.05.013

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In order to improve the stability of polymer thin-film transistors（PTFTs）,PTFTs based on poly（3-hexyl-thiophene）（P3HT） thin films were fabricated on silicon substrate,with SiO2 as the gate insulator and with gold as the source and drain electrodes.Then,the electrical characteristics and air-stability of the devices were investigated,and the mechanism of the instability in air was discussed.The results indicate that,with the increase of exposure time,both the saturation current and the threshold voltage of the devices exposed to ambient air increase ob-viously,that the moisture of ambient air is the key to the device characteristics,and that the passivation treatment with a photoresist layer can effectively improve the stability of the devices exposed to ambient air and increase the carrier mobility by about 3 times.

Computer Science & Technology

Improvement of Fusion of Conflicting Evidence Based on Deviation

Zhang Qi Liu Qun

2010, 38(5):  71-75.  doi:10.3969/j.issn.1000-565X.2010.05.014

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In the Dempster-Shafer evidence theory,the traditional D-S evidence combination rule fails to identify the actual conditions with highly conflicting evidence,which may result in contradicting conclusions.In order to solve this problem,this paper proposes an improved algorithm for the fusion of conflicting evidence,which detects and eliminates the conflicting evidence by calculating the deviation from all evidence to the average support level of the proposition,and amends the results to combine the evidence from different recognition frameworks.Numerical results show that the proposed method can effectively deal with the conflicts and achieve accurate identification,and that it is prior to other typical algorithms in terms of convergence and reliability.

A RCR Clock Synchronization Model with Drift Compensation

Quan Yu-juan Liu Gui-xiong Liu Bo Hong Xiao-bin

2010, 38(5):  76-79,85.  doi:10.3969/j.issn.1000-565X.2010.05.015

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Aiming at the high-accuracy clock synchronization with low cost in the industrial measurement and control system based on Ethernet,this paper presents a RCR（Remote Clock Reading） clock synchronization model with drift compensation,which is predominant in the precision of synchronization and the simplification of synchronization judgment and computation.Then,the architecture of the model is presented by integrating Timestamp Digi-tal Phase-Locked Loop in drift compensation,and the corresponding simulation is performed.Simulated results show that,as compared with the conventional message delay-based clock synchronization method NTP,the proposed model is more accurate,with an accuracy increase of one order of magnitude at least.

A Random and Scale-Free Hybrid P2P Worm Propagation Model

Chen Jun-hua Hu Chang-zhen Shi Feng Wei Sheng-jun

2010, 38(5):  80-85.  doi:10.3969/j.issn.1000-565X.2010.05.016

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In order to overcome the shortcomings of the existing models that use only the node degree distruibution to construct the worm network,a worm propagation model with both random and preferential attachments is proposed,which considers both the property of scale-free network and the characteristics of real P2P network communication,and introduces a adjustment parameter representing the new node connection probability.Then,the evolution mechanism of the model is investigated based on the mean-field theory through Matlab simulation.Theoretical and simulated results show that the connection between the suitable nodes selected from the worm network and the newly-infected host is tightly related to the connection probability and the node attraction,and that the established worm network is scale-free.

Break of the C^＊- Scheme Symmetry Caused by Projection

Yuan Feng Hu Yu-pu Ou Hai-wen Zhao Dong

2010, 38(5):  86-89.  doi:10.3969/j.issn.1000-565X.2010.05.017

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The SFLASH cryptographic scheme is a C^＊-scheme with specific parameters.It has been broken by Dubois et al with differential cryptanalytic attacks.This paper reviews the basic attacks to the SFLASH scheme,and points out that a successful attack mainly depends on the symmetry of the SFLASH scheme.Moreover,the symmetry of the C^＊-scheme is investigated,and the fact that projection can break the symmetry of the C^＊-scheme is also strictly proved.The results indicate that the SFLASH scheme with projection can effectively withstand diffe-rential attacks.

Design and Implementation of High-Speed Coprocessor for Elliptic Curve Cryptography

He De-biao Chen Jian-hua Hu Jin

2010, 38(5):  90-94.  doi:10.3969/j.issn.1000-565X.2010.05.018

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In order to enhance the performance of the processor for elliptic curve cryptography,an improved alogorithm of Montgomery modular multiplication is proposed,and a pipelined hardware structure for the algorithm is constructed.Then,the computation of point addition and point double of elliptic curve are optimized to fully take the advantages of modular multiplication.Thus,the point multiplication with 256b length parameters costs only 232704 clock cycles.The implementation on Cyclone II EP2C35 shows that the coprocessor needs 21000 slices and can fi-nish 1287 point multiplicaions per second for 256b length.

Mechanical Engineering

Multifunctional Digital Inverter Power Supply Based on ARM

Xue Jia-xiang Meng Wan-jun Xiong Dan-feng Gao Li-wen Yao Ping

2010, 38(5):  95-99,132.  doi:10.3969/j.issn.1000-565X.2010.05.019

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In order to realize various controls of different welding methods,a multifunctional digital inverter power supply is designed based on a central controller of Advanced RISC Machines（ARM）.Then,a digital human-computer interaction system based on ARM and Complex Programmable Logic Device（CPLD） is designed,which,combined with software design,implements the conversion and selection of such welding methods as CO2 gas metal arc welding,pulse MIG welding and manual metal arc welding.Finally,the processing properties of the designed multifunctional power supply are investigated according to the current and voltage signals acquired by a wavelet analyzer.The results indicate that the designed power supply with high practicability meets the requirements of diffe-rent welding processes and implements the multifunctionality of digital inverter power supply.

All-Position Automatic Welding Process for Tube Sheet of Heat Exchanger

Wang Zhen-min Zhang Dong Li Jin Huang Shi-sheng

2010, 38(5):  100-104.  doi:10.3969/j.issn.1000-565X.2010.05.020

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In this paper,the characteristics of the all-position automatic welding procsss for the titanium alloy tube sheet of heat exchanger were analyzed in detail,and some experiments were carried out by using a self-developed full-digital tube sheet welding system.Then,the effects of the main process parameters on the welding quality were explored,and optimal conditions for the welding were determined,that is,a peak current of 80～100A,a base current of 20～30A,a pulse current frequency of 5～10Hz,a duty ratio of 50%,a rotating speed of 3～4r/min and a pulse mode for the current rising and falling.Finally,the correctness of the optimal conditions was verified by the on-site welding of tube sheet of heat exchanger for a 1GW supercritical thermal-power generating unit.

Shaping Law of Matrix-Hole by Electrochemical Machining with Template Cathode

Li Dong-lin Zhu Di Li Han-song

2010, 38(5):  105-109.  doi:10.3969/j.issn.1000-565X.2010.05.021

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In this paper,first,template cathode is applied to the electrochemical machining of matrix-hole,and the corresponding shaping law is investigated.Next,a mathematical model to describe the actual machining process is established.Then,by considering the effects of nonlinear electrolyte,the parametric finite element method is adopted to simulate and numerically analyze the erosion process.Finally,some experiments are performed to verify the proposed model.The results indicate that the simulated erosion depth and diameter accord well with the actual ones,that the two-side electrochemical machining with template cathode helps to reduce the taper of the matrix-hole and shorten the machining time,and that the electrochemical machining with template cathode helps to obtain matrix-hole on metal sheet with low cost and high efficiency

Balling Phenomenon in Selective Laser Melting Process

Wu Wei-hui Yang Yong-qiang Wang Di

2010, 38(5):  110-115.  doi:10.3969/j.issn.1000-565X.2010.05.022

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In order to obtain metal parts with high density and accuracy,the balling phenomenon in selective laser melting（SLM） process should be eliminated.In this paper,the evolution mechanism and weakening method of balling are theoretically analyzed,finding that the change of processing parameters,such as laser power,scan speed and powder layer thickness can effectively weaken the balling because there is sufficient melting amount of the substrate.When the substrate is melted to a certain degree,the fresh molten pool is divided into an upper pool formed by metal powders and a lower one formed by a part of substrate.The former always has a tendency of balling due to the liquid-gas interfacial tension,while the latter without balling can obstruct the balling course of the former.Thus,if there is enough metal liquid in the lower pool,the balling of the upper pool during the SLM can be completely eliminated.The above-mentioned statements have been validated by the SLM experiments at a laser power of 150W or 80W and various scan speed and powder layer thickness,with Cu-based alloy powders in an ave-rage diameter of 75μm as material.

Model Reconstruction and CAM Process of Molar Crown

Lei Xiao-bao Liao Wen-he Zhang Lin Dai Ning Yang Feng

2010, 38(5):  116-121.  doi:10.3969/j.issn.1000-565X.2010.05.023

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Molar crown used in dental restoration is unique in design and processing due to its complex profile structure.In this paper,by using the reverse reconstruction technology,the point cloud data of molar crown are obtained,which are used to reconstruct and re-design part models.Then,by analyzing the processing technology through theoretical analysis,simulation and experiment,reasonable milling parameters are selected to eliminate the effects of tool and workpiece deformation on the milling quality and to reduce the machining error due to the chatter of part and tool.Finally,in view of the characteristics of molar crown,a suitable NC tool path is generated,and a molar crown meeting the design requirements is machined.The proposed method gives a reference to the machining of parts with complex structure.

Numerical Simulation of Coupling of Melt Flow and Die Deformation in T Die

Ma Xiang-jun He He-zhi

2010, 38(5):  122-126.  doi:10.3969/j.issn.1000-565X.2010.05.024

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In order to investigate the flux uniformity of melt at the outlet of T die,the melt flow and die deformation in a T die are analyzed by a coupling numerical simulation with CFD software Polyflow.The results show that the deformation of the flow channel surface along mold thickness nonlinearly varies in the extrusion direction and the die width direction,which results in great discrepancy between the simulated melt flux uniformity at the outlet and the theoretical one without considering die deformation.Moreover,it is pointed out that,with the increase of extrusion output,the slit deformation along the mold thickness increases and the melt flux uniformity at the oulet decreases,and that opposite results can be obtained when the die thickness increases.

Interactive Aid Technology for Virtual Assembly Manipulation

Zhang Dan Zuo Dun-wen Jiao Guang-ming Xue Shan-liang Li Jian-ping Zhou Hua-lin

2010, 38(5):  127-132.  doi:10.3969/j.issn.1000-565X.2010.05.025

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In order to improve the precision and efficiency of assembly manipulation in virtual assembly systems,first,a method to capture the assembly intention is proposed based on the constraint element-bounding box.Next,according to the feature parameters and fitting types of constraint elements,the pose transform is classifed into three cases： placing a point onto a line,placing a point onto a plane and being parallel a line to a line.Then,a precise positioning solving algorithm of constraints is proposed based on the pose transform of element decomposition.Moreover,the motion navigation for assembly is realized by solving the degree of freedom of the parts and mapping the motion component in the target constraint direction.Finally,a typical assembly case is studied to present the interactive aid process of assembly manipulation and demonstrate the effectiveness of the algorithm.The proposed algorithm has been successfully applied to the desktop virtual assembly system for aerospace products.

Biological Engineering

Investigation into Novel Nanocomposites as Non-Viral Gene Carrier

Wang Xiao-ying Liu Bo Lin Lu Wu Jun Sun Run-cang

2010, 38(5):  133-138.  doi:10.3969/j.issn.1000-565X.2010.05.026

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In order to obtain ideal non-viral gene carriers,trisaccharide-g-chitosan（TCS） was synthesized and was intercalated into rectorite（REC） to prepare novel nanocomposite.The product was then characterized by means of XRD and TEM,with its cellular compatibility being also analyzed.Moreover,REC,TCS and the prepared nanocomposite were respectively combined with plasmid DNA to form novel complexes,whose gene transfection effects in vitro were also evaluated.The results indicate that REC,TCS and the prepared nanocomposite all have good cellular compatibility,that the TCS/DNA complex is about 75nm in size at a N/P ratio of 3,that the addition of REC may increase the size up to 191nm,that the stability of TCS/DNA complex is positively correlated to the relative molecular mass of TCS and may degrade due to the addition of REC,and that TCS/REC-DNA complex can enter into hepatoma cells with fluorescence expression.It is thus concluded that TCS/REC nanocomposite is a potential non-viral gene carrier.

Response of Metabolic Pathway of Trehalose in Heat-Resistant Yeast Saccharomyces cerevisiae to Heat Stress

Ye Yan-rui Zhu Yi Li Li-li Lin Ying Du Hong-li Han Shuang-yan

2010, 38(5):  139-143.  doi:10.3969/j.issn.1000-565X.2010.05.027

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In order to fully reveal the heat-response mechenism of yeast,the content of trehalose in heat-resistant yeast Saccharomyces cerevisiae under heat stress was determined,and the expression of the genes involved in the trehalose metabolism was analyzed via the real-time quantitative polymerase chain reaction.The results show that,under the heat stress at 42℃,the content of intracellular trehalose significantly is up to 0.20g per gram of dry cell after 240min,which is about 4 times that without heat stress,and that,with the further prolonging of stress time,the content of intracullar trehalose decreases.The change of expression of the genes involved in the trehalose metabolism shows high consistency with that of the content of intracullular trehalose,which means that trehalose plays an important role in the adaptive process of yeast to a high temperature.

Cloning and Expression of Type Ⅲ Polyketide Synthase Gene in Fallopia multiflora

Sheng Shu-jing Zhao Shu-jin

2010, 38(5):  144-148.  doi:10.3969/j.issn.1000-565X.2010.05.028

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In order to regulate the secondary metabolic pathway of a Chinese traditional medicinal material Fallopia multiflora by genetic engineering technology,a gene named FmPKS2（GenBank accession number： GQ984139） was cloned via the rapid amplification of complementary DNA end and bioinformatics analysis.The gene consists of 1498bp nucleotides for coding sequence,encodes 392 amino acids with a predicted relative molecular mass of 43160 and an isoelectric point of 5.85,and contains several highly hydrophobic regions with a hydrophobic coefficient of-0.154.Phylogenetic analysis reveals that FmPKS2 shares the closed relationship with chalcone synthase of polygonaceae family.The transcription of FmPKS2 can be found in all different tissues of Fallopia multiflora,with the highest quantity in rhizomes.