Table of Content

25 April 2005, Volume 33 Issue 4

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Wear Characteristics of Ceramic Tools in Hard Turning of Iron-Base Sintered Alloys

Han Li-fa Xia Wei Xiao Zhi-yu Zhu Quan-li Li Yuan-yuan

2005, 33(4):  1-4. 

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On the basis of the experimental investigation into the hard turning of iron.base sintered alloys by Al₂O₃ /(W,Ti)C ceramic tools,the wear characteristics and failure mechanism of the tools were analyzed.and the effects of cutting parameters and material property on the tool wear were discussed.The results indicate that Al₂O₃ /(W,Ti)C  ceramic tools are effective for the hard turning of iron-base sintered alloys．and that the norlnal wear m0des of the tools are mainly the abrasive wear accompanied by micro-chipping and fracture and the adhesive wear . while at a higher cutting speed,the tool failure is mainly due to the fracture on the cutting edge.

Neural Network-Based Characterization of Flaws Tested by Ultrasoni

Luo Xiong-biao Chen Tie-qun

2005, 33(4):  5-9. 

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This paper proposes a method for flaw characterization on the basis of neural networks.In this me-thod ,a selection of the shape parameters defining the pulse-echo envelope reflected from a flaw is carried out by Fischer linear discriminant analysis.The selected parameters are then used as the inputs of neural networks to train the propo sed intelligent flaw characterization system. Moreover,probabilistic neural networks and back pmpagation neural networks are respe ctively adopted to determine the sizes and numbers of flaws.Experimental results for 1 35 systematic weld flaws(crack,slag and porosity)indicate that the proposed method is effective in the flaw characterization with great classification rate.

Harmonic Magnetic Field Analysis of Brushless Doubly-Fed Machines for Adjustable Speed Drives

Yang Xiang-yu Cai Xiao-ming

2005, 33(4):  10-14. 

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Aiming at the particularity of the windings in BDFM (Brushless Doubly-Fed Machine),the magnetic filed between the stator power winding and the rotor winding,as well as that between the stator control winding and the rotor winding,is coupled,thus producing the rotor winding current. The harmonic magnetic field resulting from the curents of the stator power winding,the stator control winding and the rotor winding of BDFM is also analyzed.Furtherm ore,the harmonic magnetic filed reciprocity among the above.mentioned curents is discussed. Thus,a theoretical basis for the design and harm onic analysis of BDFM is laid.

Improved Detecting Method for Harmonic and Fundamental Active and Reactive Currents

Xie Yun-xiang Chen Kun-peng Deng Yan-ping Gong Chen

2005, 33(4):  15-19. 

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In the case of unsymmetrical three-phase voltage, the phase-lock loop in the traditional i_p-i_q detecting method cannot be used to detect the phase of the positive sequence voltage. As a result.there exist errors in the transient active and reactive currents.To solve this problem,an improved i_p-i_q  detecting method is put forward.In this method,a fundamental positive sequence voltage unit based on the low.pass fiher. which can detect the phase of the positive sequence voltage,is adopted to replace the traditional voltage detecting circuit.Thus.the fun-damental active and reactive curents in the case of unsymmetrical three.phase voltage can be detected. The cor-rectness and feasibility of the proposed method are finally verified by a simulation analysi

Design of a Special Real-Time Multi-Task Operation System for Intelligent Electrical Apparatus

Ouyang Sen

2005, 33(4):  20-23,33. 

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In this paper,the characteristics of the Real·Time Multi-Task Operation System (RTOS)are intro-duced.A special RTOS(S-RTOS)is then designed based on a detailed analysis of the working characteristics of the intelligent electrical apparatus.The proposed S-RTOS overcomes such shortcomings of the traditional sequent structure software as complexity in the code structure,poor transportability and inconvenient extension. Further-more,some advanced designs are adopted in S·RTOS,including the real·time design,the resource control,the task monitoring,the interruption management,etc.Essentials of the S·RTOS design relating to the schedule mode and the task distribution are also described in detail.The verification of the S-RTOS’s schedule core by application is presented at the end of the paper

Generation of Chaos-Based SVPWM and Analysis of Its Frequency Spectral Property

Lu Yi-min Zhang Bo Mao Zong-yuan

2005, 33(4):  24-28. 

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A new space vector pulse-width modulation strategy, namely,CSVPW M,is proposed based on the chaos theory.Unlike the conventional SVPW M with fixed switching frequency, CSVPW M uses a chaotic changing switc-hing frequency to spread the harmonics continuously into a wideband area, so that the peak harm onics can greatlv be reduced.The proposed SVPW M scheme is then simulated on an induction motor fed by a voItage source invert-er.The results show that the motor operates in a similar way as with conventional SVPW M supplying. and that larger harmonic voltage and current are effectively suppressed. The proposed method would be a new way to reduce the electromagnetic noise caused by harm onic

Blind Watermarking Algorithm Based on Wavelet Transformand Visual Perception Characteristics

Wo Yan Han Guo-qiang

2005, 33(4):  29-33. 

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In this paper,an adaptive blind watermarking algorithm based on the wavelet transform and the human visual perception characteristics is proposed by drawing on the concept of the human perception-based image com-pression.In this algorithm ,the carrier image is first decomposed by means of the wavelet transform,and the wave-let coefficients of the image are classified into 9 kinds according to the characteristics of the illumination mask,the
texture mask and the edge mask in the visual system.Then,the bilevel waterm arking image is disaranged for 3 times,thus obtaining three random waterm arking sequences,which,according to the classification of the wavelet coefi cients,are finally embedded into 3 bands of carrier wavelet(‘oeflq(’ients with different intensities.The pro-posed algorithm can detect watermarking images without the help of the original carier images and the original wa· termarking images.Experimental resu lts show that the proposed algorithm is robust enough to some image degrada-tion processes such as cropping,J PE( compression,noise adding,image enhancing and filtering.

Establishment of Dedicated Short-Range Comm unication Protocol Model

Zhong Hui-ling Xu Jian-min Peng Xuan-rong

2005, 33(4):  34-38. 

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A configuration of DSRC(Dedicated Short-Range Communication)protocol which meets the communi-cation environment in China and the need of multi-application is proposed, with the development background of DSRC protocol and the existing national standards introduced.The flame format and the vehicle-r0ad c0mmunica-tion process of the protocol are then described.On this basis,a mathematical model of the protocol is established.The assumptions of the model and some data that would be used in the solution of the model are finaIIy Dresented

Form-Finding Analyses of Membrane Structures with Elastic Bars

Han Da-jian Su Jian-hua

2005, 33(4):  39-44. 

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hen applying the general methods for the form-finding of membrane structures,the connecting nodes between the membrane structure and the supporting structure are regarded as fixed nod es.and the dis-placements of the supporting structure at the connecting nodes are not talcen into account. thus resulting in the diference between form -finding results and actual situations To solve this problem, the interaction between the
membrane structure and the supporting structure in the form-finding process is analyzed based on the Force Den-sity Method.Correspo nding software for the form-finding is then programmed. Finally,two examples are pre-sented to verify the feasibility of the proposed method .

Experimental Study of Unbonded PC Flat Slab-T-Shaped Column Connections Under Reversed Loads

Li Guang-xing Cai Jian Su Jie Wu Yuan-qing

2005, 33(4):  45-49. 

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Based on the experimental study of six unbonded prestressed concrete fiat slab-T-shaped column connec-tions under low-cycle reversed loads．the loading processes and the failure features of the connection specimens were analyzed.The effects of the section parameters of the T-shaped column and the unbalanced moments in differ-ent directions on the performance of the connections,such as the stiffness,the degradation of the bearing ability,the energy-consumption ability and the distortion-recovery ability,were also analyzed by comparison.Moreover,the seismic behavior of the connections was also evaluated.The results indicate that the connections are of excellent seismic behavior,and that the web length c l of the T-shaped column is decisive to the seismic behavior of the connections.

Bridge Damage Identification via Multi Measurement with a Moving Mass

Li Da-jun Huo Da Han Qiang

2005, 33(4):  50-52,78. 

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A new damage identification method is proposed for testing bridge structures.In this method,a moving mass is used to measure the structures in different positions.The measured nature frequencies are used as the only index to determ ine other model parameters,thus identifying the damage of the structures.Moreover,the theoretical model of the proposed method is established and the corresponding equations are deduced.A numerical simulation is finally carried out to verify the effectiveness of the proposed method.

Effect of Aerodynamic Coupling Among Modes on Buffeting Redponse of Bridges

zeng Xian-wu Han Da-jian

2005, 33(4):  53-58. 

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The bufeting analysis of bridges has traditionally been accomplished by the single-mode-based SRSS (Square Root of the Sum of the Squares)method.As the main spans of bridges become longer and Ionger,the efect of the aerodynamic coupling among modes becomes so significant that it should not be neglected any more.In this paper,ten transfer functions are defined to further investigate the efect of the aerodynamic coupiing among mod es by analyzing the variation of the transfer functions with wind velocity. This investigati0n is based on the multimod e buffeting analysis procedure proposed by Scanlan. A torsional coupling ystem with 2 degrees of freedom is used as the object,and the characteristics and mechanism of the aerodynamic coupling are discussed.

Selection of Experim ental Routes for the Investigation into Bus Driving Cycles in Big Cities

Zhang Quan Jin Wen-zhou

2005, 33(4):  59-62. 

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In the investigation of the driving cycles of vehicles. the selection of experimental routes is known to be a significant factor in achieving objecitiveness and representativeness 0f the measured and resolved driving cycles.In this paper,the process of selecting experimental routes for the investigation into bus driving cycles in Guangzhou is introduced.A double-key-factor method for the selection is proposed according to on.site investigations and ana.lyses.This method is based on the average transiting speed and the standard deviation of transiting speed between two stations.The proposed method is applied to the selection of 1 5 experimental routes for the investigation into the bus driving cycles in Guangzhou．Data analysis result shows that the 1 5 routes fully represent the bus driving cycles in Guangzhou.

Optimization Method of Toll Discount Rate in Electronic Toll Collection Systems

Liu Wei-ming Li Rong

2005, 33(4):  63-68. 

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In order to establish proper toll discount rate and thus adopt and popularize the ETC(Electronic Toll Col-lection)technique reasonably,in this paper,the disaggregate method is applied to respectively analyze the rela-tionships between the fare discount rate and the selection of ETC technologies,average delay of the system, as well as the ratio of cost increment to benefit increment.Based on the analyses.an optimized model of fare discount rate is proposed,which minimizes the average delay and the ratio of cost increment to benefit increment. Moreover.an optimization algorithm on the basis of golden section method is presented.Thus, the optimum discount rate in an ETC system with certain roadway configuration can be calculated.

Numerical Simulation of Penetration of Composite Ceramic/Metal Armours

Zhang Xiao-qing Yao Xiao-hu Yang Gui-tong Huang Xiao-qing

2005, 33(4):  69-72. 

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The numerical simulation of the penetration of composite ceramic/metal armours was carried out bv using a large-scMe nonlinear Finite Element code IS-DYNA. Some processes in the penetration, such as the forming process of the conoid-shaped zone of the fragmented ceramic,the bending and cracking processes of the metal back-up plate,the mushrooming of the projectile and the vanishing process of the projectile head,were then investiga-ted.Furthermore,the curves of the coordinates of the projectile.armor interface and the rear end of the Drojectile varied with time were given.The simulated results are compared with the results of a theoretical analVSis aS well as the experimental results.It is concluded that the three kinds of results match fairly well with each other. The effect of the ratio of the ceramic thickness to the metal backup plate thickness on the impacticn-resistance abilitv of the composite arm our is also analyzed,with the result indicating that there is an optimum ratio for the impaction-resist-ance ability.This conclusion is valuable for the design of composite ceramic/metal armours.

Retention Efect of Ground Blast-Furnace Slag on the Leaching of Cr(VI)from Hardened Fly Ashes

2005, 33(4):  73-78. 

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The retention effcts of two kinds of ground blast-furnace slag(GBFS)on the leaching of Cr(VI)from hardened fly ash slurry and the hardened fly ash compacted at the optimum moisture content were investigated in this paper.The results show that:(1)the leaching of Cr(VI)from hardened fly ashes can be effectively restrained by GBFS with proper treatment;(2)the retention efect of GBFS on the leaching of Cr(VI)depends on the types of fly ashes,the preparation method of specimens and the fineness and content of GBFS;(3)better retention effect is achieved when GBFS and OPC(Ordinary Portland Cement)are used together;and(4)generally speaking,the leaching of Cr(VI)from hardened fly ashes decreases with the prolonging of curing time.It is also indicated that the formation of ettringite and C- S- H gel in hardened fly ashes contributes significantly to the fixation and stabili.zation of Cr(VI).

Mechanism Analysis of the Antioxidant Activities of Hesperidin and Its Derivatives

Zhu Si-ming Yu Shu-juan Yang Lian-sheng Gao Wen-hong Zhang De-cong

2005, 33(4):  79-82,91. 

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Th e antioxidant mechanism of hesperidin and its derivatives was discussed bv means of the Complete Neglect of Differential Overlap(CNDO).The results indicate that,for 4 antioxidants,namelv,hesperidin.dios-min,methylhesperidin and hesperidin chalcone.their antioxidant activities mainly result from the complexation of a flavonoid with metal ions and are not due to the effect of deoxidization. Moreover.neohesperidin dihydrochalcone was found to be a good antioxidant with excellent complexation effect and deoxidization ability. The complexation of hesperidin with Fe” was finally testified by experiment

Mathematical M odel and M echanism of Supercritical Fluid Extraction Enhanced by Ultrasonic

Ding Cai-mei Qiu Tai-qiu Luo Deng-lin

2005, 33(4):  83-86. 

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By using the interpolated ultrasonically-enhanced supercritical fluid extraction(USFE)device designed by the researchers.the mathematical model and mechanism of USFE were investigated.The experimental results indicate that the proposed model not only proves the enhancement of supercritical fluid extraction by ultrasonic,but also predicts well the USFE process and the supercritical fluid extraction(SFE)process.Meanwhile,it can reflect the actual extraction process.It iS also indicated that the low-frequency ultrasonic has a greater effect on USFE than the high-frequency ultrasonic and that the mechanism of USFE lies in the mechanical fluctuant effect and the ther-real effect caused by ultrasonic in microenvironment.

Improvement of Gel Properties of Bighead(Aristichthy Nobilis) by Two Protein Additives

2005, 33(4):  87-91. 

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The effects of two protein additives,namely,egg white powder and wheat gluten,on the gel properties of bighead surimi were investigated by testing the texture and microstructure of the surimi gels.SDS·polyacrylamide gel electrophoresis(SDS-PAGE)was used to investigate the corresponding mechanism.The results show that,with the two additives.the gel properties of bighead surimi are obviously improved and a gel network with a firm and u-niform structure is form ed.The research also shows that higher additive concentration will result in greater improve-ment,and that egg white powder can increase the whiteness of bighead surimi gels,while wheat gluten has an op-posite effect on the whiteness.SDS·PAGE results indicate that egg white powder and wheat gluten have little effect on the intensity of the myosin heavy chain(MHC)of bighead surim gels.

Adaptive String Method for the Study of Rare Events

Dou Hai-yong

2005, 33(4):  92-95. 

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An adaptive string method is proposed based on the string method. In this method,a moving mesh meth-od is adopted to control the tangent movement of mesh points.Bigger density of the mesh points near these states can be obtained by choosing an appropriate monitor function in the moving mesh method, thus accurately locating the positions of the critical points on the minimal energy path and calculating the energies at the critical points. The proposed method is then applied to the study of the double well potential system and the Mueller potential problem.The results show that the proposed method is a reliable numerical method for studying rare events in complex sys-tems.

Weighted Generalized M ean Curvature Operator with Subcritical Exponent Growth

Yang Jun Shen Yao-tian

2005, 33(4):  96-100. 

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The existence of the nontrivial solution of a weighted generalized mean curvature-div((1+I ▽uI ²)^p-2/2▽u)=λIuI ^r-2u+μ|u|^q-2/|x|^su in some c0nditions,such as the Dirichlet boundary c0nditi0n and the condition that r and q are less than the critical exponent,is investigated in this paper. In the investigation,the Sobolev-Hardy ine.quality,the theorem of almost everywhere convergence of the gradient u_n and the Mountain Pass Lemma Satisfying the(PS)_c conditions are adopted.Thus,the dificulties in verifying the Mountain Pass geometric conditions and the PS conditions are conquered.