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15 January 2004, Volume 25 Issue 1 Previous Issue    Next Issue
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3D reconstruction of medicine image on ray-casting basis Hu, Ying (1); Wang, Huai-Zhi (2); Xu, Xin-He (1) 2004, 25 (1):  1-4.  DOI: - Abstract ( 373 )   HTML   PDF (272KB) ( 1156 )   Compared with different reconstruct algorithms and taking account of the features of medicine images and actual requirements, a scheme based on the ray-casting technique was proposed to solve the problem of the 3D reconstruction of medical images. To improve the rendering speed of ray casting and make the technique shown in the scheme a practical routine in medical applications, a synthesized accelerate algorithm based on space leaping and series correlativity was suggested. Finally, a 3D reconstruction system of medicine image in the proposed scheme was implemented on a PC platform to obtain a nearly real-time interactive speed. Because the kernel of all these reconstruction algorithms is the ray-casting technique, a high quality result of reconstruction can be acquired. At the same time, the complexity of the whole system can thus be reduced greatly with the R and D efficiency improved. The results are very helpful to the development of the 3D reconstruction of medicine images. References | Related Articles | Metrics

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Rolling force modeling for No.5 mill in a cold continuous rolling tandem Liu, Xing-Gang (1); Tan, Shu-Bin (1); Cui, Jian-Jiang (1); Xu, Xin-He (1) 2004, 25 (1):  5-8.  DOI: - Abstract ( 279 )   HTML   PDF (159KB) ( 749 )   Taking account of the elastic/plastic deformation of both rolled piece and roller in cold continuous rolling process, the deformation zone of rolled piece can be divided into three subzones, i.e. the entry elastic deformation, plastic deformation and exit elastic deformation. The rolling force in the plastic deformation and entry elastic deformation subzones is computed iteratively with numerical integration. The rolling force in the exit elastic deformation subzones is calculated also. At last, the model to calculate rolling force of No.5 mill is obtained via the sum of the two rolling forces calculated. Some simulations were done using different steel grades specifications of rolled strips of which the relevant data were recorded in situ. This force model is thus proved accurate and able to meet the precision requirements of precomputation for cold continuous rolling process. References | Related Articles | Metrics

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Optimization of open-loop control law on standing process of inverted single pendulum Hou, Xiang-Lin (1); Cong, De-Hong (2); Xu, Xin-He (2) 2004, 25 (1):  9-12.  DOI: - Abstract ( 377 )   HTML   PDF (311KB) ( 1187 )   Based on optimal control, the process control of a nonlinear single inverted pendulum is studied. An optimization method with penalty term is proposed to compute open-loop control law. Compared with ordinary numerical methods, this method adopts optimal step length instead of fixed step length so as to set precisely the control per unit time interval in computation. The computation for the control law on the swing-up process of single inverted pendulum is thus programmed. A simulative analysis of the process is carried out, of which the results show that a high-precision control law is available to control the process of nonlinear system. References | Related Articles | Metrics

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Robust stabilization of nonlinear discrete-time systems based on T-S model Mi, Yang (1); Jing, Yuan-Wei (1) 2004, 25 (1):  13-16.  DOI: - Abstract ( 236 )   HTML   PDF (161KB) ( 488 )   The quadratic stabilization of nonlinear discrete-time systems is studied based on T-S fuzzy model. Introducing parametric uncertainty terms into building the T-S model for nonlinear discrete-time systems with uncertainty terms, the fuzzy model may approach to the original system. Based on Lyapunov stability theory, a condition for the existence of state-feedback control laws is derived to satisfy the quadratic stabilization. A linear matrix inequality equivalent to the condition is obtained, which can easily be solved using Matlab tool box. The method proposed is verified feasible through a simulative example of truck-trailer. References | Related Articles | Metrics

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New approach to design of nonlinear robust excitation controller Zhang, Xiu-Hua (1); Zhang, Qing-Ling (1); Xie, Yan-Hong (2) 2004, 25 (1):  17-19.  DOI: - Abstract ( 249 )   HTML   PDF (225KB) ( 626 )   A kind of nonlinear robust controllers for power systems was studied. Applying the latest achievements in the field of control theory, i.e. Hamilton-Jacobi inequality of nonlinear control theory, an approach to the design of nonlinear robust excitation controller is proposed. It takes account of the nonlinearity of power systems and the interference effect, so it has higher versatility. Nonlinear characteristics are kept completely in the design process without linear technique used, so as to enhance the capability of the system and enable the control theory to be applied further to power systems. Compared with the excitation controllers designed via conventional linearization, the newly designed ones have superiorities in simpler construction and more efficient stability. References | Related Articles | Metrics

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Determination of principal components in PCA model on basis of fault reconstruction Li, Yuan (1); Xie, Zhi (1); Wang, Gang (2) 2004, 25 (1):  20-23.  DOI: - Abstract ( 262 )   HTML   PDF (1215KB) ( 1053 )   Based on the theory of fault reconstruction, the determination of the principal components in PCA (principal component analysis) model is studied, the performance of PCA model is analyzed. In the fault diagnosis based on PCA theory, the faulty variables can be reconstructed in the direction of vectorized faults data, with the variance of reconstruction error (VRE) projected separately onto principal component sub-space (PCS) and residual sub-space (RS). An optimal reconstruction is convincing only if the sum of all VREs in both PCS and RS come to minimum, among which the corresponding principal components are referred to as optimum principal components. An evaluation is carried out for the performance of PCA model by virtue of cumulative percent variance (CPV) and multi-correlation coefficients. The results show that the principal components determined as above in PCA model can ensure enough information in PCS. The reasonableness and effectiveness of the determination method is proved through a fault diagnosis for industrial PCV polymerization process. References | Related Articles | Metrics

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Landmarks optimization of triangulation of autonomous mobile robot Zhang, Xiang-De (1); Niu, Ji-Xiang (1); Dong, Zai-Li (2) 2004, 25 (1):  24-27.  DOI: - Abstract ( 347 )   HTML   PDF (1755KB) ( 949 )   A geometric precision criterion is deduced for robot triangulation, showing the effect of landmark set-up on robot localization. It is proved that the precision of robot localization will be the highest one if all the distances between the robot and every landmark are equal to each other and then both the angles included between two adjacent landmarks to the robot are also equal to each other in case the number of relevant landmarks is not less than three. An optimal selection algorithm of landmarks is thus given. Experimental results showed further the validity of the conclusion as above. References | Related Articles | Metrics

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Dynamic lightpath protection in WDM grooming networks He, Rong-Xi (1); Wang, Guang-Xing (1) 2004, 25 (1):  28-31.  DOI: - Abstract ( 236 )   HTML   PDF (163KB) ( 504 )   Under the constraints of the number of transceivers per node and wavelength continuity, the problem of provisioning dependable connections with different bandwidth granularities in wavelength division multiplexing (WDM) mesh networks was investigated. A novel protection graph model (PGM) was proposed to represent current state of the network such as transceivers, wavelengths, protected-lightpaths and bandwidth. Based on PGM, two dynamically dedicated lightpath-protection algorithms named minimal wavelength-link method (MWM) and minimal transceiver method (MTM) were developed. Based on dynamic traffic of different loads, the performances of the two schemes have been investigated via simulations. The results show that MWM outperforms MTM in blocking probability and traffic throughput, while the simulation time of MTM is less than that of MWM. References | Related Articles | Metrics

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Approach to eliminating transient route oscillations in IBGP Qu, Rong-Xin (1); Zhang, Chun-Hong (1); Gao, Yuan (1) 2004, 25 (1):  36-39.  DOI: - Abstract ( 251 )   HTML   PDF (171KB) ( 474 )   This paper studies the transient route oscillation in IBGP (Internal Border Gateway Protocol) when the route reflection is working as one of the mechanisms extended from BGP (Border Gateway Protocol). An abstract IBGP model is given based on graph theory to analyze dynamically the behavior characteristics of a transient route oscillation system in IBGP. Based on these characteristics, an asymmetric configuration with MRAI (Minimum Route Advertisement Interval, a BGP-specific timer) used is proposed to eliminate the transient route oscillations in IBGP and improve the stability and convergence of IBGP system. Then, the abstract IBGP model is used once more to analyze dynamically the behavior characteristics of the asymmetric configuration to prove its effectiveness. Finally, the effects of symmetric and asymmetric configurations on the stability and convergence of IBGP are analyzed by means of simulation. References | Related Articles | Metrics

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High temperature mechanical properties of low carbon steel Di, Hong-Shuang (1); Kang, Xiang-Dong (1); Wang, Guo-Dong (1); Liu, Xiang-Hua (1) 2004, 25 (1):  40-43.  DOI: - Abstract ( 787 )   HTML   PDF (203KB) ( 2087 )   The hot ductility and strength of low carbon steel were studied by using Gleeble-1500 thermal stress/strain simulator according to the hot deformation schedules of heating and solidifying separately. θd and θs, zero ductility temperature (ZDT) and zero strength temperature (ZST) respectively, were measured. Meanwhile, crack sensitivity and fracture microscopic structure were analyzed. The results show that the measurements of solidifying method are closer to the actuality. The brittle temperature of tested steel is from 1350°C to melting point. The cross section contraction rate of the test steel is greater than 60% in the range from 1100-1300°C, which shows the steel has higher resistance to high temperature cracking. The θd and θs of the steel are 1350°C and 1400°C respectively. References | Related Articles | Metrics

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Comparison and analysis of different testing methods of minimum ignition energy of dust cloud Li, Xin-Guang (1); Dong, Hong-Guang (1); Radandt, S. (2); He, Ji-Cheng (3) 2004, 25 (1):  44-47.  DOI: - Abstract ( 358 )   HTML   PDF (158KB) ( 1754 )   The three important time/space-dependent influencing factors on the measurement of dust, were tested quantitatively by a 1.2 L Hartmann bomb, 20 L-sphere and vibratory sieving tube, as the testing apparatus for dust cloud, and the results were compared. Then, a special instrument was used together with the three apparatus to measure the minimum ignition energy of dust cloud. The results were also compared. Based on such results the influencing factors on the measurement of the minimum ignition energy were discussed. It is revealed that the influencing factors on the dust dispersity are the way to disperse dust and the magnitude of initial turbulivity. With respect to the dust dispersion effect, 20 L-sphere is the best, the 1.2 L Hartmann bomb is the second, vibratory sieving tube is the poor one. The fact implies that the vibratory sieving tube is improper to testing minimum ignition energy. References | Related Articles | Metrics

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Microstructure of Mg alloy ZK60 in different magnetic fields Xu, Guang-Ming (1); Bao, Wei-Ping (1); Cui, Jian-Zhong (1); Gu, Xiao-Feng (1) 2004, 25 (1):  48-50.  DOI: - Abstract ( 234 )   HTML   PDF (503KB) ( 560 )   The microstructure and distribution of alloying elements of magnesium alloy ZK60 were studied experimentally and comparatively, which was solidified under the actions of no magnetic field, low-frequency a.c. electromagnetic field and magnetostatic field, separately. In addition, the distributions of different electromagnetic fields in the solidification process were simulated numerically. The results showed that applying either low-frequency a.c. electromagnetic field or magnetostatic field on the alloy in its solidification process could refine effectively grains and affect the distribution of alloying elements within the grain and on grain boundaries, with discontinuous eutectic net structure found on grain boundaries. The effect of grain refining by magnetostatic field is evidently better than that by low-frequency a.c. electromagnetic field. Furthermore, the eutectic compounds aggregated on grain boundaries are reduced greatly, and lots of dispersive sphere-like particles of compounds are found within grains and in the vicinity of grain boundaries, which are beneficial to improving the overall properties of the magnesium alloy. References | Related Articles | Metrics

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Properties of sinter-forged WC/FY-1 steel matrix composites He, Feng-Ming (1); Xiu, Zhi-Meng (1); He, Chun-Lin (1); Ru, Hong-Qiang (1) 2004, 25 (1):  51-54.  DOI: - Abstract ( 237 )   HTML   PDF (216KB) ( 584 )   The specimens of WC/FY-1 steel matrix composites were prepared through sintering, forging and alloying processes in order to investigate the microstructures and the properties. The results show that the density, strength, hardness and wearability of the sinter-forged FY-1 steels increase greatly with the FY-1 master alloy powder addition, but the impact toughness decreases. The addition of FY-1 master alloy powder to the WC/FY-1 steel matrix composites can activate the sintering process by liquid sintering. On the other hand, the WC additive improves significantly wearability of the WC/FY-1 steel matrix composites, by which the wear-out of 15% WC/FY-1 steel matrix composite is just one filth of the W18CV4V alloy steel that is used widely to make guide rolls at present. The properties of the 15% WC/FY- 1 steel matrix composite can meet the requirement for material to make guide rollers for high-speed wire rolling mill. It is expected that the composites will be applies to roll making soon. References | Related Articles | Metrics

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Effect of electromagnetic field on graphite formation in cast iron Zhang, Guo-Zhi (1); Zhang, Xiao-Li (1); Hu, Huo-Sheng (1); Jia, Guang-Lin (1) 2004, 25 (1):  55-57.  DOI: - Abstract ( 308 )   HTML   PDF (291KB) ( 741 )   A pulse (commutative traveling wave) electromagnetic field was designed as an experimental setup for solidification, where the effect of pulse electromagnetic field on the graphite in cast iron in solidification process and its solidified microstructure was investigated. The results showed that in solidified grey cast iron the number of austenite dendrites reduced clearly with graphite coarsened. After nodulizing process, the number of nodular graphite decreases and the rate of vermicular graphite increases greatly. A new approach to stabilizing the rate of vermicular graphite of compacted graphite cast iron is thus proposed. The mechanism that how the electromagnetic field affects the formation of graphite is discussed. The effect of electromagnetic stirring of electromagnetic field and thermal effect of induced current can damage the stability of the austenite shell around graphite cores, thus bring about the growth of branched graphite to form vermicular graphite. The interference of pulse electromagnetic field can stabilize the rate of vermicular graphite only if the residue of Mg and Re is sufficient or nearly sufficient, otherwise, the insufficient Mg and Re as additives will cause the interference to form flake graphite. References | Related Articles | Metrics

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Viscosity measurement and modeling for slag systems CuCr alloys prepared via Al thermit-SHS (I) Zhang, Ting-An (1); Dou, Zhi-He (1); Xu, Shu-Xiang (2); Yang, Huan (1) 2004, 25 (1):  58-61.  DOI: - Abstract ( 229 )   HTML   PDF (191KB) ( 739 )   The viscosity model proposed by Sichen Du and S. Seetharaman et al was applied as a reference to the slag systems without SiO2, based on the constitutional characteristics of Al2O3 slag systems. A new viscosity model was developed for viscosity measurement, focusing on the reaction of aluminium thermit. The feasibility of taking CaO-Al2O3 and CaO-Al2O3-MgO systems as the constituents of the slag systems of CuCr alloy prepared via aluminium thermit-SHS is studied, according to the principle of additive selection in combination with relevant phase diagrams. An analysis was made comparing the experimental measurements with the viscosity values calculated in accordance to the new model. The result shows that it is successful to use the new model to determine the viscosity value of the slag systems which are constituted via the reaction of aluminium thermit. References | Related Articles | Metrics

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Transient transfer matrix method for complicated rotor systems with rub-impact fault Yao, Hong-Liang (1); Liu, Chang-Li (1); Li, He (1); Wen, Bang-Chun (1) 2004, 25 (1):  62-65.  DOI: - Abstract ( 253 )   HTML   The Raccati transfer matrix method and Newmark-β method are combined together to analyze the transient and steady responses from rotor systems with rub-impact fault. Multi-iteration method was used to obtain the accurate value of transient rub-impacting force. The transient transfer matrix method proposed above is applied to complicated rotor system with rub-impact fault, such as a rotor system involving multi-disk, multi-step, or others, with factors such as gyroscopic moment and nonlinear oil-force taken into account. At last, a two-step rotor system with partial rub-impact fault pertaining to nonlinear stiffness is analyzed using the method, by which a lot of nonlinearities are found, and the feasibility of the method is therefore verified. References | Related Articles | Metrics

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Experiment and modeling of dynamic response system on virtual lathe Yang, Guo-Zhe (1); Xu, Feng (1); Gong, Ya-Dong (1); Wang, Wan-Shan (1) 2004, 25 (1):  70-73.  DOI: - Abstract ( 199 )   HTML   PDF (262KB) ( 729 )   Aiming at the vibration of virtual lathe's cutting operations, an experiment was done. Based on experimental results, the cutting vibrations are decomposed into three parts, i.e. the random vibration, forced vibrations and the regenerated chatter, and each of them is modeled. The effect of spindle rotation on the amplitude responses of forced vibration is analyzed. The models developed are applied to NC simulation of cutting vibration process to predict the physical process of metal working by lathes, so as to improve the applicability of the virtual cutting software. Compared the results from simulation and from experiment for chattering process, the program developed can be regarded as reliable. References | Related Articles | Metrics

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Modules and configuration design of reconfigurable modular robots Li, Shu-Jun (1); Zhang, Yan-Li (2); Zhao, Ming-Yang (3) 2004, 25 (1):  78-81.  DOI: - Abstract ( 289 )   HTML   PDF (124KB) ( 2150 )   To meet the requirement of rapid reconfiguration of robot systems, the structure of modules of modular robots was studied. 7 kinds of modules were developed, including 3 as joints with 1 DOF, 2 as links, 1 as base and 1 as connecting module for different series of modules. The design of joint modules takes into account not only kinematic independence but also control independence. The connective parts of all modules were designed in cylindrical form for convenient reconfiguration and increasing rigidity. A modular base can thus be set up by the modules of which each has a series of dimensions. The configurations of 3 DOF series robot system were presented. The feasibility of these modules was verified. References | Related Articles | Metrics

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Technological investigation on taper grinding for hybrid bearing ceramic ball Lu, Feng (1); Wu, Yu-Hou (2); Zhang, Ke (2) 2004, 25 (1):  82-85.  DOI: - Abstract ( 214 )   HTML   PDF (189KB) ( 1053 )   The HIPSN ceramic balls were made by taper-grinding technological process. The effect of such parameters as grinding pressure/speed and time interval of adding abrasive additive on the grinding efficiency was analyzed. How to improve the rate of utilization of diamond abrasive and reduce the cost of grinding operation were particularly investigated, and the results indicated that the rational and stable grinding technology should be as follows: the optimum grinding pressure to single workpiece is 6-8 N at a speed of 450-800 r/min, and the favorable time interval of adding abrasive additive is about 60 min. The HIPSN ceramic balls can be ground well using the process mentioned above by which the surface roughness of HIPSN ceramic ball can be up to 0.01-0.02 μm with a spheroid error 0.09-0.18 μm, both are available to meet the special applications. References | Related Articles | Metrics

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Crack resistance of composite beams of steel-high strength concrete slab Xu, Wei (1); Zhu, Fu-Sheng (1); Wang, Lian-Guang (2); Xu, Feng (2) 2004, 25 (1):  92-95.  DOI: - Abstract ( 226 )   HTML   PDF (190KB) ( 431 )   4 composite beams of steel-high strength concrete were tested to investigate their crack resistance. It was found tiny cracks appear firstly on the bottom surface of concrete slab when about 40% of limit load is acting on a beam. Then the cracks increase and further extend out gradually between loading points, and at last, some of them go through the slab from bottom to top. The relationships between strain and load have been obtained for both steel and concrete slab of composite beam, with their bearing mechanisms discussed correspondingly. The formulas to calculate the load causing cracks are given to the beam on elastic basis. The results of calculation and testing show that they are in good conformity to each other. In addition, a width formula is also given to the composite steel-high strength concrete slab. References | Related Articles | Metrics

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- - 2004, 25 (1):  96-98.  DOI: - Abstract ( 115 )   HTML   PDF (160KB) ( 715 )   - References | Related Articles | Metrics

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- - 2004, 25 (1):  99-102.  DOI: - Abstract ( 162 )   HTML   PDF (208KB) ( 1353 )   - References | Related Articles | Metrics