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15 September 2003, Volume 24 Issue 9 Previous Issue    Next Issue
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Effects of tempering temperature on microstructure and properties of a newly developed cold-working die steel Sun, Rong-Yao (1); Ru, Hong-Qiang (1); Zhao, Yuan (1); Liu, Chun-Ming (1) 2003, 24 (9):  817-819.  DOI: - Abstract ( 221 )   HTML   PDF (828KB) ( 936 )   A cold-working die steel was developed through adjusting allowing components and heat-treatment process to improve the conventional steel AISI D2 of which a lot of carbides in ledeburite offer very high wearability in combination with low impact toughness which is easy to lead D2 to break up in use and hard of forging and linear cutting. The effects of tempering temperature on the microstructure, hardness and impact toughness of the new steel (test steel) were investigated by means of metallographical microscope, hardmeter and impact taster. The results show that it has advantages of less carbides and smaller particle size if quenched at 1050°C and tempered at 500°C and its impact toughness and hardness are both higher than D2 at various tempering temperatures, e.g. HRC60 and 4.5×105 J/m2 at 500°C respectively. With coarse, big and uneven carbides removed, its structure is improved greatly, thus eliminating the break-up inactivation and prolonging the service life. References | Related Articles | Metrics

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Valence electron structure of austenite in cobalt-free high-strength high-toughness steel Geng, Ping (1); Liu, Jing (1); Dong, Li-Na (1) 2003, 24 (9):  820-823.  DOI: - Abstract ( 189 )   HTML   PDF (985KB) ( 559 )   Taking advantage of the Empirical Electron Theory (EET) of solid and molecules, an analysis was made to the valence electron structure of cells either containing or not containing carbon of austenite in Co-free high-strength high-toughness. The effect of those cells containing carbon cells was taken into account preferably in phase transformation process because the value nA of theirs is greater than that of the cells containing no carbon. In the cells containing carbon the alloying elements Ni, Si, Cr and Mo form a gathering borough together with carbon atoms, and the forces binding Ni and Si to C are greater than those binding Cr and Mo to C. The gathering borough will reduce the diffusivity of carbon, hinder dislocation from moving and delay the martensite transformation so as to keep dislocation density high in matrix, thus keeping a certain number of residual austenite in the steel, making austenitic grain size thinner and minimizing the size of martensite transformed. All of the results will benefit improving the toughness of the steel. References | Related Articles | Metrics

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Synthesis of Sialon-SiC composites and its application Yu, Jing-Kun (1); Dai, Wen-Bin (1); Dai, Shu-Ping (1) 2003, 24 (9):  824-827.  DOI: - Abstract ( 228 )   HTML   PDF (197KB) ( 1037 )   Take pyrophyllite and carbon black as raw materials to synthesize the Sialon-SiC composites by carbothermal reduction process. Then, apply the composites as additive to unshaped Al2O3-C refractories so as to investigate the effect of heating temperature on the synthesis process and the effect of addition on the properties of refractories. The results show that the composites can be easily synthesized if adding carbon black moderately into pyrophyllite and heating the mixture to 1540°C in nitrogen atmosphere. It is proved that the resistance to oxidation/slag corrosion and hot modulus of rupture of such refractories can be improved obviously if adding moderately the synthesized Sialon-SiC composites into them. References | Related Articles | Metrics

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Phase analysis and production mechanism of iron carbide Hui, Yin-An (1); Wang, De-Yong (1); Jiang, Mao-Fa (1) 2003, 24 (9):  828-831.  DOI: - Abstract ( 275 )   HTML   PDF (370KB) ( 1133 )   Based on thermodynamic analysis, the production mechanism and path of iron carbide deoxidized from iron ore in fluid bed were studied. The results show that (1) ferric oxides are deoxidized according to the theory of Gradual Deoxidizing at 700°C, and iron carbide comes from the infiltrating reaction of CO; (2) iron carbide comes mainly from the reaction of FeO to CO with partly from the reaction of metallic Fe deoxidized from iron ore to CO at 586°C to 628°C; (3) when the temperature is lower than 586°C, iron carbide in product sample comes mainly from the reaction of Fe3O4 to CO, and the content of magnetite is higher correspondingly. By means of Mossbauer spectrum and X-ray diffraction, the phase analysis we made verified that iron carbide exits in product sample. All the results here will lay a theoretic foundation for industrial production of iron carbide. References | Related Articles | Metrics

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Dissolution of alumina in molten cryolite Xu, Jun-Li (1); Shi, Zhong-Ning (1); Gao, Bing-Liang (1); Qiu, Zhu-Xian (1) 2003, 24 (9):  832-834.  DOI: - Abstract ( 579 )   HTML   PDF (113KB) ( 1786 )   The dissolution behavior of alumina in molten cryolite was investigated by using a transparent quartz crucible, where the dissolution process was recorded by a video camera. The influencing factors of dissolution velocity of alumina were analyzed and discussed. The results show that there are two stages in dissolution process, i.e., the rapid dissolution and the peeling-off dissolution of alumina crusted with electrolyte. The alumina dissolves at different velocities in molten cryolite because when feeding the alumina into the crucible, the temperature of electrolyte decreases so as to form alumina/electrolyte agglomerate on the surface of electrolyte to reduce the contact area between alumina and cryolite. The dissolution velocity of alumina rates to the stirring rate, preheating temperature of alumina, melt temperature and the kinds of alumina used. References | Related Articles | Metrics

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On the steam sensor for solid electrolyte of ZrC2 mixed with Y2O3 Han, Yuan-Shan (1); Wang, Chang-Zhen (1); Tian, Yan-Wen (1); Zhai, Yu-Chun (1) 2003, 24 (9):  835-838.  DOI: - Abstract ( 242 )   HTML   PDF (979KB) ( 523 )   A steam sensor composed of concentration cells has been developed using a small tube made from ZrO2 mixed with Y2O3, which was sintered to form solid electrolyte according to a certain regime. The reference electrode used was made from H2C2O4 mixed with H2C2O4·2H2O or Na2SO4 mixed with Na2SO4·l0H2O, of which either equilibrium steam pressure was given by a physic-chemical principle. It is revealed different partial pressures of steam can be obtained if adding some nonvolatile solutes into solvent. So, the other electrode for measurement was made from pure water or KOH solution of different concentrations, thus forming concentration cells for steam. Sensitivity experiments have been done separately for the cells as above in the ranges from 0 to 35°C and from 8 to 23°C . The results revealed that the EMF of cells, E, changes regularly with lg(PH2O(I)/PH2O(II)) where PH2O(I) and PH2O(II) are the partial pressure of steam at the electrode for measurement and at reference electrode, respectively, i.e., E decreases with increase of temperature and E increases with the increase of PH2O(I) at constant temperature. A fit linear relationship is found between E and lg(PH2O(I)/PH2O(II)). References | Related Articles | Metrics

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Coupling effect in a synchronous vibration system Zhang, Tian-Xia (1); E, Xiao-Yu (1) 2003, 24 (9):  839-842.  DOI: - Abstract ( 919 )   HTML   PDF (317KB) ( 1525 )   Self-synchronous vibration system is a mechanical dynamic system with features of synergistic motion. In the system, the coupling effect comes from the interaction between the rotary motions of two eccentric rotors, thus changing the motional characteristics and forms of the system. A differential equation was derived with an analytical method of nonlinear vibration for the coupling motion of two eccentric rotors to describe mathematically the coupling parameters of the system. Based on the phase space theory, the nonlinear characteristics of coupling motion were analyzed, as well as the influence of coupling intensity on the equilibrium state. The variation range of coupling parameters was also defined. Furthermore, the synchronization development course of two eccentric rotors was studied in depth, and the necessary coupling conditions to form a synchronization state are deducted. Finally, engineering applications of synchronous vibration system were discussed, including the design and selection of structural parameters. References | Related Articles | Metrics

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Effects of nonlinear friction force on chaotic motion of rotor-bearing system at rub-impact faults Luo, Yue-Gang (1); Jin, Zhi-Hao (1); Liu, Chang-Li (1); Wen, Bang-Chun (1) 2003, 24 (9):  843-846.  DOI: - Abstract ( 224 )   HTML   PDF (256KB) ( 1173 )   Considering the strong nonlinear oil-film force and influence of nonlinear friction force, a dynamic model was set up for the rotor-bearing system at rub-impact faults. The nonlinear dynamic behaviors in running were investigated widely on a basis of modern nonlinear dynamics and rotor dynamics theory with the influence of the coefficient of relative speed between rotary and stationary parts on the bifurcation and chaotic motion of the system discussed. Lots of nonlinear phenomena investigated revealed that within the subcritical speed range both the quasi-period and chaotic motion regions increase with the increase of relative speed coefficient. However, within the supercritical speed range, the chaotic motion region decreases, but the rub-impact forces increase and the quasi-period motions become gradually the period 3 ones. These provide a theoretic basis reference for the failure diagnosis to the rotor-bearing systems at rub-impact faults. References | Related Articles | Metrics

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Direct-profile-design method for generating noncircular gear pairs Lin, Jing (1); Xie, Li-Yang (1) 2003, 24 (9):  847-850.  DOI: - Abstract ( 220 )   HTML   PDF (189KB) ( 925 )   A working pressure angle was defined as a function of rotating angle of noncircular gears, called Working-Pressure-Angle or WFA function. A method for generating noncircular gear pairs was thus developed and named. Direct-Profile-Design (DPD) method, where WPA function is used to obtain the desired tooth profiles of generated pairs, was put forward. The length of a tooth profile normal between the tooth profile and pitch curve was defined as the normal length of a tooth profile. This length relates to WPA by a first order differential equation. The differential equation ensures one tooth profile to be engaged with the other profile. As demonstrated, this new method is applicable to any type of gear pairs including circular or noncircular. In addition, using this method is relatively easier to generate new tooth profiles and investigate the geometrical and mechanical properties of gear pairs, and the desired geometrical and mechanical properties will come true in design. References | Related Articles | Metrics

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Implementation and examination of multi-agent based modeling framework of manufacturing system Yuan, Feng (1); Xie, Li-Yang (1) 2003, 24 (9):  851-853.  DOI: - Abstract ( 204 )   HTML   PDF (138KB) ( 660 )   Introducing the traditional function- and process-based modeling frameworks of manufacturing system, the characteristics of software object, software component and intelligent agent were discussed. Then, a new modeling framework of manufacturing system on multi-agent basis was presented and implemented, which was comprised of software object dimension at autonomous levels, software life cycle dimension and multi-view model dimension. Based on the engineering methodology of agent-oriented software, the software system of multi-agent based framework of manufacturing system was developed. It is shown that software agent is more autonomous and intelligent than software object and software component, and the multi-agent based framework is suitable for open manufacturing system with distributed data and decentralized control. It will be a new approach to software system integration of manufacturing system. References | Related Articles | Metrics

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Reliability model of mechanical transmission system ( III ) - Reliability optimization using single gear reducer Sun, Zhi-Li (1); Chen, Liang-Yu (1); He, En-Shan (1); Ding, Jin-Yuan (1) 2003, 24 (9):  854-857.  DOI: - Abstract ( 490 )   HTML   PDF (302KB) ( 1568 )   Setting up a reliability design model for mechanical transmission system and describing the treatment of correlated variables, a single cylindrical gear reducer was exemplified to illustrate the design of reliability optimization with all of random influencing factors on reducer's operation taken into account. The objective function of reliability design was derived taking variables independent transformation as theoretic basis by which the correlated intensities among individual parts can all be transformed into independent variables from each other, thus making sure the correctness and exactness in calculation. With various constraint conditions defined, a solution was obtained using the penalty function for exterior points to have the advantage of unlimited initial points. Thus, a better result came true through optimization. Finally, the reliability and exactness of this approach was verified by Monte Carlo method and the result showed the similarity between them. References | Related Articles | Metrics

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Analysis on tooth surface curvature of equal-base-circle bevel gear Gong, Yun-Peng (1); Li, Wei-Ping (2); Zhang, Wei-Hua (1) 2003, 24 (9):  858-861.  DOI: - Abstract ( 260 )   HTML   PDF (160KB) ( 451 )   Equal-base-circle bevel gears can be cut precisely in an economical way, which is of importance to large size bevel gears. Taking tooth trace modification into account, the equation of cutter center trace was derived. To carry out tooth profile modification, the modified cutter profile equation was determined for equal-base-circle bevel gear profiles. According to differential geometry theory, the primary curvature and primary direction and normal curvature in different directions of cutter surface were obtained. Based on the theory of conjugate tooth surface, the primary curvature, primary direction and normal unit vector of gear tooth surface were derived from the geometry structure of cutter surface and the special relative motion between the cutter and tooth blank, which can be used to predetermine the meshing properties. All of these lay a foundation for gearing analysis, modification and strength calculation. The modification design of equal-base-circle bevel gear, which is available to improve meshing quality, can be carried out easily by NC technique. References | Related Articles | Metrics

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- - 2003, 24 (9):  862-865.  DOI: - Abstract ( 270 )   HTML   PDF (238KB) ( 2067 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  866-869.  DOI: - Abstract ( 225 )   HTML   PDF (192KB) ( 797 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  870-873.  DOI: - Abstract ( 260 )   HTML   PDF (150KB) ( 664 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  874-876.  DOI: - Abstract ( 272 )   HTML   PDF (150KB) ( 874 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  877-880.  DOI: - Abstract ( 248 )   HTML   PDF (1780KB) ( 592 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  881-884.  DOI: - Abstract ( 250 )   HTML   PDF (1147KB) ( 809 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  885-888.  DOI: - Abstract ( 286 )   HTML   PDF (323KB) ( 833 )   - References | Related Articles | Metrics

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- - 2003, 24 (9):  889-891.  DOI: - Abstract ( 237 )   HTML   PDF (136KB) ( 647 )   - References | Related Articles | Metrics

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Sliding-mode control of biped robot Zhou, Yun-Long (1); Xiang, Long-Jiang (1); Xu, Xin-He (1) 2003, 24 (9):  892-895.  DOI: - Abstract ( 242 )   HTML   PDF (264KB) ( 662 )   Using Newton-Euller method, a dynamics model of biped robot with 12 degrees of freedom was built, and then a sliding-mode control model of biped robot was also built. Stability analysis of sliding-mode control is made by a simpler Lyapunov function, and the angle acceleration of 12 degrees of freedom is compensated using the sliding-mode control method. To prove the effectiveness of sliding mode control method on trajectory tracking control, a simulation experiment was done, where the random errors of some given ranges were added to every joint angle instead of the errors caused by such factors as the structure parameters, moment of inertia and friction. The experiment results show that the trajectory tracking errors of angle and angle velocity at each joint angle are small insomuch that the expected effect comes true and prove that the sliding-mode control method Is available to control the trajectory tracking of biped robot with 12 degrees of freedom. References | Related Articles | Metrics

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Blow-up and chaos of the solutions to a category of nonlinear wave equations Chi, Dong-Xuan (1); Wang, De-Jia (1); Zhu, Wei-Yong (2) 2003, 24 (9):  896-899.  DOI: - Abstract ( 235 )   HTML   PDF (246KB) ( 651 )   The nonlinear wave equations are a category of nonlinear evolution equations describing mainly the things changing with time and having waved shape. Because most of these equations feature the interruption and chaos of their evolution traces in solution, their dynamics states contain blow-up and chaos in general. The state of a category of nonlinear wave equations with preventable blow-up factor and the blow-up problem of the solutions to these equations are studied. By way of approximation, the conditions of interruption occurrence are given. With the interruptive solutions discussed, the state at their interrupting point is analyzed. The chaos phenomenon is verified at the interrupting point of the interruptive solutions under certain conditions, according to the Li-Yorke theorem. References | Related Articles | Metrics

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Applications of fourth-order cumulant algorithm to blind beamforming Wang, Jin-Kuan (1); Liu, Zhi-Gang (1); Xue, Yan-Bo (1); Liu, Fu-Lai (1) 2003, 24 (9):  900-902.  DOI: - Abstract ( 285 )   HTML   PDF (174KB) ( 1146 )   Features of beamforming algorithms were analyzed. Considering blind beamforming algorithms without knowing the array manifold, direction of arrival, training sequence, the correlation matrix including noise and jamming and so on, a blind beamformer based on fourth-order cumulant was designed. Because of making directly use of high-order cumulant statistical information on received signals, both the interferences by Gauss noise and nonGauss noise can be eliminated effectively. The simulation test results show that this algorithm is more adaptable to multipath environment and has advantages of quicker convergence and better robustness to S/N change in comparison with MVDR beamformer. References | Related Articles | Metrics

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Adsorption of zinc ions by diatomite Shen, Yan-Bai (1); Zhu, Yi-Min (1); Wei, De-Zhou (1) 2003, 24 (9):  907-910.  DOI: - Abstract ( 334 )   HTML   PDF (177KB) ( 1337 )   The adsorption process of Zn2+ by white diatomite from Changbai Mountain Area in Jilin Province was investigated, with various influencing factors discussed. Test results show that the adsorption process is efficient and quick, in which an equilibrated adsorption can be got within about 10 minutes and better adsorption effect will come true with pH value under neutral conditions than under acidic conditions. Solution temperature affects obviously the adsorption effect. Up to 99.71% Zn2+ can be removed using 10 g/L diatomite to adsorb it from the solution with a concentration of 9.8 mg/L Zn2+ . After a secondary adsorption, the removing rate approaches to 100%. By SEM it is found that the surface and pores of diatomite are the main adsorbing positions. References | Related Articles | Metrics

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Tensor analysis of seepage flow from structural plane network of rock mass Yang, Tian-Hong (1); Zhang, Yong-Bin (1); Leng, Xue-Feng (1); Tang, Chun-An (1) 2003, 24 (9):  911-914.  DOI: - Abstract ( 245 )   HTML   PDF (182KB) ( 613 )   Study on permeation characteristics of engineering rock mass is a key technique to the analysis of seepage flow and stability design. Based on actual statistics used in the probability model for the typical structural plane of rock mass, a typical fracture network model is set up by discrete medium method, and a way to calculate the equivalent permeability coefficient tensor of the structural plane network of rock mass is put forward. An equivalent continuous medium model to reflect the anisotropy of seepage flow of rock mass is used to analyze the seepage flow problems of rock mass in areas of interest, which is set up specially for hydrogeological objects with sloping edges in mine-fields. As shown by examples, the technique is available to not only make a macroscopic seepage flow analysis in engineering rock mass, but indicate in depth the essence of seepage flow from fissures. References | Related Articles | Metrics

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- - 2003, 24 (9):  915-918.  DOI: - Abstract ( 166 )   HTML   PDF (153KB) ( 673 )   - References | Related Articles | Metrics