Journal of South China University of Technology(Natural Science Edition)

Effect of NO on SO₂ Oxidation Adsorption over CatalystSupport γ -Al₂O₃

Chen Ying, Li Xue- hui, Xu Jian- chang, et al

2004, 32(11): 1-5.

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The adsorption profiles and storage capabilities of NO and SO 2 over the catalyst support γ-Al 2 O 3 were ex-plored at an adsorption temperature of423K and with different atmospheres （with oxygen or without oxygen）and the states of adsorbed SO 2 and NO were studied by DFIRFS （Diffuse Reflection Infrared Spectroscopy）．Thusthe effect of NO on SO 2 oxidation adsorption at a low temperature was observed．The results show thatat a low temperatureNO can promote the oxidation adsorption of SO 2 over γ-Al 2 O 3 and that the lattice oxygen of γ-Al 2 O 3 is directly taken part in the promotion reaction．The promotion mechanism is that there arises a surface reaction of chelating nitro com-plexes resulting from γ-Al 2 O 3 adsorbing NO with the vicinal weakly adsorbed Al—O—SO 2 and that the surface reac-tion makes the weakly adsorbed Al—O—SO 2 form stable sulfate ions （SO 42－） and oxygen vacanciesrelease NOand supply the oxygen vacancies with oxygen in gas phase to form lattice oxygenthus setting the surface reaction go-ing on and on.

Measurement of Power Quality Disturbance Based on Wavelet Transform

Zhu Feng- feng Ren Zhen Hu Guo- sheng

2004, 32(11): 6-9,14.

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The quantificational detection for the change of voltage amplitude was investigated in this paper．Firsttwo conceptions were definedthat isthe amplitude and adjusting amplitude based on two real wavelet standard trans-forms．Nextit was proved thatif the two real wavelets meet some conditionsand one is an even function and the other is an odd onethe adjusting amplitudes based on the two real wavelet standard transforms are always equal to1in the wel- l balanced durationwhile the adjusting amplitudes are equal to the ratio of vo- l tage amplitude in the wel- lbalanced duration to that in the disturbance duration．Finallythe adjusting amplitudes of two selected real wavelets were used to detect the voltage waveform aberrance．Simulated results show that the novel amplitude detection figures can not only find accurately out the start point and stop point of faults but also quantitatively display the changing mag-nitude of voltage.

Wavelet Transform-based OFDM-CDMA High-speed Power Line Communications Systems

Zhou Le- rong Guo Jing- hong Wei Gang

2004, 32(11): 10-14.

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The implementation of high-speed data communication through power lines is always a difficulty in the fields of power communications and power system automation．In this paperthe equivalent M-band discrete wavelet transmission mode of OFDM transmission systems was derived based on wavelet transform．A new OFDM-CDMA communications system for high-speed power line communications was then presented on the basis of orthogonal Mband discrete wavelet transform．The computer simulation results indicate that the proposed system is of much better ability to suppress inter-channel interferenceinter-symbol interferencemult-i user interference and noise interference and is applicable to the high-speed power line communications.

Design of Servo Controller of Permanent Magnet Synchronization Motor Based on Fuzzy PI Contro

Yang Xiang-yu Cai Xiao-ming Yao Jia

2004, 32(11): 15-18,27.

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The fuzzy PI control of the servo controller of permanent magnet synchronization motor （PMSM） was presented as a replacement of the traditional PI control to improve the controlling performance of PMSM．In this method by detecting the rotor speed error and stator current error as well as their variation rate between the instant value and the referenced valuethe parameters P and I can be decided by looking up on-line empirical datathus realizing the servo control of PMSM．Simulation results prove thatcompared with the traditional PI controlfuzzy PI control can effectively increase the response speed of the systemreduce the torque pulses of the motor in both transient and stable states and improve the system stability.

Investigation into the Five-phase Space Vector PWM

Jin A-i juan Li Shao-long Li Hang-tian

2004, 32(11): 19-23.

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In order to overcome the limitation of power semiconductors against the capacity of the frequency control system of three-phase induction machinea mult-i phase induction machine was presented by the phase extension of three-phase induction machine．On the basis of three-phase space vector PWM（SVPWM）a novel theory and an implementation method of five-phase SVPWM suitable for the frequency control system of five-phase induction machine were then proposed．High modulation ratio of voltage and sine wave of current were finally obtained by the simulation via Matlab／Simulink．Five-phase SVPWM can be applied to the frequency control system of five-phase induction machine and is of excellent control ability.

Numerical Simulation of the Heat Transfer in an Earth-air Heat Exchange System

Wu Hu-i jun Zhu Dong-sheng Sun Jia-long

2004, 32(11): 24-27.

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The outlet temperature and heat transfer performance of an earth-air heat exchange system were numerically simulated by the superposition of natural ground temperature field and the air cooling effect．The influences of pipe depthlength and diameter on the outlet temperature of the exchanger were also studied．It is concluded by analysis that the outlet temperature of the heat exchanger changes periodically with the periodical change of pipe inlet temperatureand thatwith the increase in the pipe depth and lengththe outlet temperature and its variation degree of the exchanger decrease．The same phenomenon is obtained from the pipe with the decrease in pipe diameter．At the same timethe cooling performance of the earth-air system increases.

Optimization of the Extraction Technique of Sargassum Fusiorme Polysaccharide via Response Surface Analysis

Li Ya-na Lin Yong-cheng She Zhi-gang

2004, 32(11): 28-32.

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For the extraction of Sargassum fusiforme polysaccharide, the experimental factors and levels were selected through single factor experiment. According to the central combination experimental design principle of box benhnken, the response surface analysis method of three factors and three levels was adopted on the basis of single factor experiment, the influencing factors of various process conditions were determined according to regression analysis, and the response surface and contour map were made with the polysaccharide extraction rate as the response value. The results showed that, The optimum conditions of water extraction of Sargassum fusiforme polysaccharide were as follows: extraction temperature 85 ℃, extraction time 2.6h, water material ratio 28 ∶ 1; When extracted once, the extraction rate of Sargassum fusiforme polysaccharide reached 11.12%.

Optimum Preheating Temperature Before Tire Vulcanization

Zeng Zhao Jiang Nan Yi Yu-hua Zhang Hai

2004, 32(11): 33-36.

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A3-D finite element model was established by using ANSYS to simulate the vulcanization process of10． 00R20-type radial tire．The effects of different preheating temperatures on the temperature field and extent field of tire vulcanization were then quantitatively analyzed．The results show that the flowing time of heated water in capsulae shortens by2min and the vulcanization time in curing machine shortens by1min with an initial vulcanization temperature increasing of10℃．At the same timethe homogeneousness of tire vulcanization state improves by10％．The results also shown that higher preheating temperature will result in shorter tire curing time in curing machine and better vulcanization homogeneousness．By synthetically considering all the factors influencing the vulcanization in preheating processit is concluded that the optimum preheating temperature is not more than105℃.

A Modal Logic-Based Measurement Method of Security Protocol

Wang Tao Guo He-qing Yao Song-tao

2004, 32(11): 37-42.

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In order to introduce the quantitatively analytical method into security protocol analysisa protocol measurement method based on modal logic was defined．This method formally specifies the parameters and approaches to measure the satisfaction of security goals of the protocol contents．On this basisapproaches of mea-suring protocol redundancy and corresponding simplification were then put forward．The method was finally applied to analyze a sample protocoldescribe the contribution of each protocol content and present the inefficacy of redundancy factors to protocol targetsthus achieving the safe simplification．The method is possessed of a main feature of applying quantitative analysis to the formal analysis of security protocoland of the advantages and limitations of modal logic methods.

Dehybridization Control of a Class of Affine Nonlinear Hybrid System

Zhang Da-ke Hu Yue-ming

2004, 32(11): 43-45,50.

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In order to solve the problem of stability of hybrid systems with arbitrary switching lawsa class of affine nonlinear hybrid system was investigated．The complete dehybridization of this class of system was firstly realized according to the order-reducing character and by designing the controlling laws of sliding mode control．The control design of the system was then carried out according to the control theories and methods applied to common continuous nonlinear systems．At lasta final sliding mode control law which ensures the stability of hybrid systems was obtained by transformation．The simulation results confirm the validity of the proposed control law．

LS-SVM Modeling Simulation for the Calcination Process of Lithopone

Zhu Yan-fei Mao Zong-yuan Tan Guang-xing

2004, 32(11): 46-50.

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In order to overcome the difficulty in the modeling of lithopone calcinationan identification algorithm based on the LS-SVM （Least Squares Support Vector Machine） was applied to the modeling of the calcination process．As the LS-SVM algorithm is of the advantages of simple structure and high speedaccording to the mechanisms of SVM and LS-SVM algorithmsa model describing the variation of rotating speed with the temperature in the calcinations process was obtained by modeling simulation．The identification performance of the proposed algorithm was finally compared with that of the ANFIS （Adaptive Neura-l fuzzy Inference System）with the conclusion that the LSSVM is more valuable when applied to the modeling of the calcination process．

Model to Determine Dispersed Homogeneous Degree of Carbon-black in Rubber Based on LS-SVM

Kang Chun-Jiang Wang Guo-Qiang Liao Qin

2004, 32(11): 51-54.

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In order to decrease the rejection ratio in the rubber-producing processthe dispersed homogeneous degree of carbon-black in rubber should be indirectlyreal time and accurately determined．Support Vector Machines based on the principle of structural risk minimization is a new machine learning method which is of excellent classification and generalization ability when being used in the small sample decision．In this papera6-band determination model of dispersed homogeneous degree of carbon-black in rubber was established on the basis of mult-i class Least Squares Support Vector Machinesand some practical data were determined by the model．The results show that the proposed model is practical and average rate of false determination reduce to3．6％and can determine the dispersed homogeneous degree of carbon-black in rubber quickly and correctly．

Motion Analysis of Four-axis WEDM Machine Tool and Its Application to NC Verification

Zhai Hong-jun, Liu Zheng-xun, An Lu-ling, et al

2004, 32(11): 55-60.

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In this paperby the motion analysis of four-axis wire-Electric Discharge Machining （WEDM） machine toolsit is concluded thatduring the machining of intricate ruled surfaces only with linear boundary curvesthe maximum inclining angle of the wire and the maximum displacements of the machining table and the wire guiding head occur on the vertices of the boundary lines．Based on the conclusionan algorithm to calculate the maximum angle and displacement is proposed and then applied to the NC verification of WEDM to avoid the motion collision and profile interference．A verification example shows that the proposed method can effectively ensure the machining accuracy．

A General Fast Algorithm for Large-magnification Super-resolution Image Reconstruction

Zhang Di Du Ming-hui

2004, 32(11): 61-65.

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In order to tackle the difficult problem that the computational complexity of super-resolution image reconstruction rapidly and exponentially increases with the increase in amplificationthis paper proposes a general fast superresolution image reconstruction algorithmin which the translation relation of multi low-resolution images is used to divide the images into several groups．Each group is then reconstructed by means of the super-resolution algorithmand the grouping-reconstructing process is continuously repeated till the desired resolution is achieved．Experimental results show a significant reduction of computational complexity of the algorithm while a basically constant visual output quality is retained．

A RS Decoder for IP Block Error Correction and Its Implementation on FPGA

Yang Bo Yin Jun-xun Shi Lei

2004, 32(11): 66-69.

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To reduce the FPGA resources that RS decoder occupiesthe algorithm of RS decoding was studied．An approach to implement RS decoding in IP block error correction system on Actel ProASIC PLUS chip was also presented． In this approachRS（10081） was adopted for error correction．Based on the complicated operationthe solution to the decoderthat isthe modified BM algorithmwas then describedwhich can save more resources than the traditional one．Experimental results indicate that the decoder can accomplish the task of IP block error correction and can accept an input data rate up to30Mbit／s．The primary architecture of ProASIC PLUS chip and the key technology of its implementation on FPGA were finally presented．

Comparison of Calculating Models of Cohesive Riverbank Stability

Wan Yan-chun Liu Yue-Qin

2004, 32(11): 70-74.

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In this paperby taking the pore water pressure and the hydrostatic confining pressure into consideration three typical calculating models of cohesive riverbank stability were presented via suitable optimization and were then applied to a practical stability measurement．The corresponding results were finally comparedwith the conclusion thatfor natural riverbanksthe predigesting model is simpler and more applicablebut is less precisewhile for the prediction of riverbank shape after failurethe probability model is betterand the precision of the layered model is the highest in the three modelsalthough its calculating load is the greatest．These three models are all applicable to the stability calculation of cohesive riverbanks with a plane-like failure．

Wind Tunnel Test of Inclined Long-span Flat Roof in Complex Circumstance

Liu Yue-xing, Wang Fan, Wu Bo, et al

2004, 32(11): 75-80.

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In order to investigate the distribution characteristics of the mean wind pressure and the fluctuating wind pressure on the inclined long-span flat roof in complex circumstancean actual construction was employed to measure its pressure by applying a rigidity model．This measurement is carried out in a simulated wind field of the aerosphere boundary．The wind-pressure coefficient distributions of the structure in different wind directions were then obtained．It is concluded by the analysis of experimental data that the pressure distribution changes with wind direction and the buildings around the structurewhich mainly exhibits three typesand that the wind load of the roof obtained by the experiment is different from that obtained by the Load Code for the Design of Building Structure．

Ruin Probability with Credit Risk Under the Effect of Interest Rate

Tu Yu-qing Liu Shen-quan

2004, 32(11): 81-85.

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In order to investigate the survival probability of insurance companies with credit risk and avoid their going bankrupta ruin model with credit risk in finite discrete time under a constant interest rate was introduced and the ruin condition was givenas well as the survival probability with credit risk in finite discrete time under a constant interest rate．By using this modelthe ruin probability and the distribution of the ruin time were derived．By the analysis of ruin probabilitythe recursive formulae for the distributions of the surpluses before and at the instant of ruintogether with the joint distribution of the two surpluses were finally obtained．

Application of Green Quasifunction Method in Elastic Torsion

Wang Hong Yuan Hong

2004, 32(11): 86-88.

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In this papera Green quas-i function is firstly set up by using the basic solution of Poissonʾs equation．This function satisfies the homogeneous boundary condition of Poissonʾs equation．Nextthe boundary value problem is changed into an integral equation by applying a Green function．Thenby establishing a normalized boundary equationthe irregularity of the kernel of integral equation is overcome．The elastic torsion can be considered as a boundary value problem of Poissonʾs equation．For any complicated areaa normalized boundary equation can always be found according to the R-function theoryso the elastic torsion problem can be transformed into a second-class Fredholm integral equation without irregularity．Numerically illustrated results show that the proposed method is of high accuracy and can be used to solve other complicated boundary value problems in mechanics and physics．

A Spherical Covering Model Used to Cure Tumors

Hong Yi Tao Zh-i sui

2004, 32(11): 89-92.

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A mathematical problem arising from the therapy of tumors was investigated．In the ultrasound-guided radio-frequency ablation to cure tumorsthe tumor is assumed to be sphere-likeand the expendable size of the ablation electrode is assumed to be a small spheroid．Medical treatment requires that all the cells on the tumor surface be killed． The mathematical problem is how to utilize the sphere with a radius r to cover the spherical surface with a radius R （r ＜R）．In this paperthe regular tetrahedron algorithm and the n-side regular prism algorithm were discussedaccording to the geometric properties of spheres and polyhedral angles and by using the method of stepwise covering．To solve the problemthe pineapple-shaped algorithm and the spherical crown stepwise covering method were proposed thus giving a minimal ablation placement algorithm which can be applied to the therapy of tumors．

C-normal Subgroups and Solvability of Finite Groups

Liu Guo-gang

2004, 32(11): 93-96.

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It is proved in this paperif some subgroups of the finite group Gsuch as the maximal subgroupSylow subgroup and its subgroupsare also C-normal subgroups of group Gsome sufficient conditions as well as necessary and sufficient conditions for the solvability of group G can be obtained．By determining whether its subgroups are Cnormal subgroupsthe solvability of group G can be determined．In the proofthe method of contradiction of the extreme minimal rank of group G is adopted．This method is a combination of induction and reduction to absurdity．Besidesa new subgruop set L（G）that isthe maximal subgroups excluding the guided group of G is introduced into the proof．

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