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15 December 2008, Volume 29 Issue 12 Previous Issue    Next Issue
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On the sliding mode control for time-delay network systems Wang, Hong-Wei (1); Jing, Yuan-Wei (1) 2008, 29 (12):  1673-1676.  DOI: - Abstract ( 269 )   HTML   PDF (1267KB) ( 540 )   To solve the problem of congestion control in TCP (transmission control protocol) networks, a novel active queue management (AQM) algorithm is presented on the basis of sliding mode control theory. (Considering the TCP linear dynamic systems with state delay and input delay, a particular linear transformation is applied to the original uncertain time-delay system to turn it into a delay-free system. Then, an optimal sliding hyperplane is designed in a new coordinate system and the control law is chosen to constrain oscillation arising from the queue length in router effectively with accurate traceability. Simulation results verified further the feasibility of such a control strategy. References | Related Articles | Metrics

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Knowledge acquisition of fault diagnosis expert system of hydraulic tube tester Zhao, Zhen (1); Hu, Xue-Fa (1); He, Da-Kuo (1); Wang, Fu-Li (1) 2008, 29 (12):  1677-1680.  DOI: - Abstract ( 258 )   HTML   PDF (1085KB) ( 535 )   The knowledge acquisition of fault diagnosis expert system of hydraulic tube tester is investigated, and a zooming knowledge acquisition method is put forward on the basis of subtraetive clustering algorithm which is applied to analyzing the boosting pressure acted by the tester with the results to be evaluated by experts. In this way, the parameters of subtraetive clustering algorithm can be readjusted in time according to the evaluation results, thus meeting the preset requirements. The knowledge that was acquired by " zooming " effect and investigation on a class of findings in depth is verified experimentally, and its validity is proved. References | Related Articles | Metrics

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OpenMP-based multi-population PSO algorithm to solve the uncapacitated facility location problem Wang, Da-Zhi (1); Yan, Yang (1); Wang, Ding-Wei (1); Wang, Hong-Feng (1) 2008, 29 (12):  1681-1684.  DOI: - Abstract ( 354 )   HTML   PDF (286KB) ( 779 )   The OpenMP-based parallel multi-population particle swarm optimization (PSO) algorithm to solve the incapacitated facility location (UFL) problem. The parallel algorithm is operating asynchronously by dividing the whole particle swarm into several sub-swarm and the particle velocity is updated with a variety of local optima. Every sub-swarm exchange its optimal particle with its neighboring swarm after the algorithm operated for a certain number of generations The parallel multi-population PSO (PMPSO) algorithm is applied to several benchmark suits collected from OR-library, and the results are compared to that of the serial multi-population PSO. It is found that the parallel multi-population PSO is time saving in execution, especially in the large scale computation it will provide higher robustness. References | Related Articles | Metrics

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Parallel simulation-based optimization on block planning of container terminals Li, Hao-Yuan (1); Wang, Ding-Wei (1) 2008, 29 (12):  1685-1688.  DOI: - Abstract ( 216 )   HTML   PDF (353KB) ( 548 )   Applying the system simulation to the discrete events of something to be modeled, and analyzing the technological process of loading and unloading at a modern container terminal as well as the relevant operational management, a simulation model is developed involving the whole operating process in a container terminal where the container ships, anchorages, berths, quay cranes, gantry cranes, internal and external container trucks, trailers, yard gates, etc., are all taken into account. To solve the block planning problem of container Terminals, the simulation-based optimization (SBO) method is proposed, where the MPI-based parallel cluster computing technique is introduced into the solving process. Thus, the tedious computation for SBO is well improved. References | Related Articles | Metrics

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On the 3D distribution of locating reference nodes Zhou, Yan (1); Zhao, Hai (1); Cao, Wei (2); Cai, Wei (1) 2008, 29 (12):  1689-1692+1710.  DOI: - Abstract ( 253 )   HTML   PDF (310KB) ( 733 )   In view of the requirements for high locating accuracy and fast response to location information in 3-D space, the region of errors due to locating an unknown node is studied on the basis of analyzing the conventional 2-phase locating algorithm. It is found that the locating accuracy can be greatly improved if there are four locating reference nodes distributed according to a certain mode which is available to provide better service for positioning. Thus, the theorem of distribution of spatial locating reference nodes (DSLRD) is proposed to design and implement a new locating reference node distribution (LRND) algorithm in 3-D space. The new algorithm will not only save greatly the computation/storage resources but ensure the real-time veracity of locating computation. References | Related Articles | Metrics

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LQI based link evaluation algorithm and its application in wireless sensor networks Zhang, Xi-Yuan (1); Zhao, Hai (1); Zhu, Jian (1); Xu, Jiu-Qiang (1) 2008, 29 (12):  1693-1696.  DOI: - Abstract ( 218 )   HTML   PDF (503KB) ( 715 )   Communication quality evaluation is crucial to upper-layer protocols' design in wireless sensor networks. A link evaluation algorithm based on mean LQI is proposed by comparing some link quality evaluation parameters. This algorithm can reduce redundant data for energy saving under the precondition of ensuring evaluation precision. Then, an improved ETX (IETX) routing metric is presented, through the new link evaluation algorithm. The performance of the IETX metric is tested with the Micaz nodes as platform, and the result shows the reliability and energy saving effect of IETX metric. References | Related Articles | Metrics

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Load-balanced routing mechanism and relevant algorithm based on MANET accessing Internet Li, Xin (1); Li, Zhe (1); Wang, Min-Xian (1) 2008, 29 (12):  1697-1701.  DOI: - Abstract ( 207 )   HTML   PDF (1085KB) ( 561 )   For the MANET accessing Internet, some gateways are in certain positions where the mobile nodes (MNs) are used intensively to access Internet so as to cause heavier loads at those gateways and weaken their performance. A load-balanced routing mechanism and relevant algorithm are therefore developed for MANET accessing Internet with dynamic gateways and multi-paths. This algorithm uses multi-path for transmission and assigns communication traffic to many candidate paths in accordance to a certain proportion and, meantime, it balances the load of gateways by choosing them to which the load should be as low as possible. The result of simulation analysis showed that this algorithm can reduce the average transmission delay of packets and improve the throughput of the networks effectively. References | Related Articles | Metrics

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The research of P2P-SIP hierarchy based communication mechanism Yang, De-Guo (1); Wang, Hui (1); Wang, Cui-Rong (1); Gao, Yuan (1) 2008, 29 (12):  1702-1705.  DOI: - Abstract ( 307 )   HTML   PDF (329KB) ( 626 )   The combination of P2P with SIP has some problems such as the instability due to P2P nodes characteristics and lack of complete and practical design. A new media communication mechanism based on P2P-SIP was therefore designed, where the hierarchy is used to form an overlay network because of the heterogeneity of the nodes involved in. Then, an algorithm was presented to form the hierarchy. Simulation results showed that the stability of the hierarchical mechanism is higher than that of existing P2P system, thus reducing both the information quantity in media communication networks and time delay for the location and registration of information resources. References | Related Articles | Metrics

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Delay-based route optimization mechanism in mobile IPv6 Xia, Li (1); Zhang, Jun-Ya (1); Liu, Dai-Qing (2); Chang, Yue (1) 2008, 29 (12):  1706-1710.  DOI: - Abstract ( 277 )   HTML   PDF (1014KB) ( 599 )   Route optimization which is a key technology to solve the problem of triangle routing in mobile IP is based on the assumption that the direct path from a correspondent node to a mobile node is more optimal than the indirect path. However, the assumption is not always the case, and the route optimization may lead lots of packets to be out-of-sequence and degrade the performance of networks. A delay-based route optimization mechanism in mobile IPv6 is therefore proposed to solve the problem, in which the HoT and CoT messages are both stamped with the time during RRP (return routability procedure), and whether the route optimization is to be done depends on the transmission delays obtained by measuring both the direct and indirect paths from the mobile nodes. Meanwhile, LAST message as the mark of ending is sent from indirect path with a timer scheme utilized to avoid out-of-sequence packets. A simulation was done to analyze the test data of the mechanism proposed. References | Related Articles | Metrics

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Micromechanism of short crack initiation and propagation in Ti-15-3 alloy Wang, Ping (1); Liang, Tian (1); Hou, Shi-Yao (1); Lei, Jia-Feng (2) 2008, 29 (12):  1711-1714.  DOI: - Abstract ( 267 )   HTML   PDF (1018KB) ( 549 )   Effects of grain misorientation angles on the short crack initiation and propagation in Ti-15-3 alloy were studied by means of electron back scattered diffraction (EBSD) and scanning electronic microscope (SEM). In Ti-15-3 alloy, 98% of misorientation angles between adjacent grains are greater than 10°. Among adjacent grains the big misorientation angles are favorable to short crack initiation, whereas the small ones are favorable to short crack propagation. If the included angle between the orientation of short crack tip and that of slip band of next grain is greater than 35°, the crack is easy to zigzag when passing through the next grain; if the angle is less than 35°, the crack propagates along the orientation slip band. When the short crack tip propagates to reach grain boundary and if the included angle between the orientation of short crack tip and that of grain boundary is less than 35°, the short crack propagates along grain boundary and if the angle is greater than 35°, a transgranular crack propagates. References | Related Articles | Metrics

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On the direct contact between work roll surfaces outside workpiece width during thin strip cold rolling Zhao, Qi-Lin (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2008, 29 (12):  1715-1717+1741.  DOI: - Abstract ( 259 )   HTML   PDF (591KB) ( 702 )   To investigate the influence of the direct contact between work roll surfaces outside workpiece width on thin strip cold rolling process, a simulation model was developed by means of influence function, with which the production data during rolling were taken to calculate the roll deformation on a four-high mill. Such distributive data as contact pressure, strip thickness and tensile stress were calculated to analyze the effect of work roll surface contact mentioned above on the distribution of rolling force, strip thickness, and tensile strength at exit and strip shape. It was found that when the work roll surface contact occurs, the rolling force decreases at the verge of strip, while the contact pressure between the surfaces of work roll and back-up roll increases at the end of back-up roll. The direct work roll contact enables both the strip crown and transverse thickness difference to decrease, thus resulting in thinning down the strip verge and it also makes the distribution of tensile stress at exit more uniform so as to improve strip shape and flatness. References | Related Articles | Metrics

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Application of self-learning to simulation for process control in continuous annealing Hua, Fu-An (1); Wang, Wen-Le (1); Li, Jian-Ping (1); Liu, Xiang-Hua (1) 2008, 29 (12):  1718-1720.  DOI: - Abstract ( 204 )   HTML   PDF (239KB) ( 676 )   Based on theoretical analysis, a mathematical model was developed to simulate the cooling process control in continuous annealing. To improve the efficiency of self-learning, a viewpoint was suggested that the radiant heat dissipation can be transformed equivalently into the adjustable convective heat dissipation coefficients in cooling process. In the model, the sample temperature is layered and the exponential smoothing is introduced to determine the adjusting coefficients for each and all temperature layers. In the actual cooling process, the flow rate of cooling gas can be adjusted by virtue of the process control system according to the adjusting coefficients for different layers. Application results indicated that process control system based on self-learning enable the temperature accuracy to be controlled within 10°C in the simulation of cooling process for continuous annealing. References | Related Articles | Metrics

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Preparation of Li/TiO2/ITO working electrode and its kinetics characteristics of heterophase reaction Bi, Xiao-Guo (1); Ding, Sen (2); Liu, Yan-Hua (1); Xiu, Zhi-Meng (1) 2008, 29 (12):  1721-1724.  DOI: - Abstract ( 250 )   HTML   PDF (285KB) ( 695 )   The working electrode was prepared by way of depositing TiO2 thin film on conductive ITO glass substrate via sol-gel method. As 3-electrode testing system was then formed combining it with SCE (saturated calomel electrode) as reference one, black platinum electrode as auxiliary one and PC + LiClO4 solution as electrolyte. The TiC2 thin film was characterized by AFM, SEM and XRD to test the cyclic volt-ampere characteristic curves of the potential of the working electrode at the scanning voltages ± 0.5 V, ± 1.0 V and ± 2.0 V. Testing results showed that on the curve at ± 2.0 V the Li+ inserting and extracting peaks appear clearly and that the Li+ plays a role as a rate determining step in the electrode process kinetics of the diffusion rate in the electrolyte and TiC2 thin film. However, no Li+ inserting and extracting peaks appear on the curves at ± 1.0V and ± 0.5 V. It implies that the potential of working electrode is the rate determining step of the electrode process kinetics. A conclusion is drawn that the scanning potential should be greater than ± 2.0 V when studying the characteristics of heterophase reaction kinetics. References | Related Articles | Metrics

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GA-NN-based predicting model of activity of multiple slag system Wu, Ling (1); Jiang, Zhou-Hua (1); Gong, Wei (1); Li, Yang (1) 2008, 29 (12):  1725-1728.  DOI: - Abstract ( 230 )   HTML   PDF (1144KB) ( 633 )   A model based on GA-NN for predicting the activity of components in multiple slag system is developed. The artificial neural nets (NN) can implement any approximation of function with simple structure, while the genetic algorithm (GA) is a globally optimized search one based on genetics and natural selection theory, which is available to implement the iteration process through allying the genetic manipulation to the individuals in colonies for their restructuring and then evolve the increasingly improved approximate solutions generation by generation in accordance to the adaptability function for individuals. GA is always used to give the weights and thresholds of neural nets. Computing and simulating the CaO-SiO2, CaO-SiO2-Al2O3 and CaO-SiO2-Al2O3-MgO slag systems, it is found that GA-NN model has high nonlinear capability and the computation results fit well with that in relevant earlier works, thus enabling the accurate prediction of the activity of components in molten slag. References | Related Articles | Metrics

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Study on enhanced ultrasonic leaching of 12CaO·7Al2O3 Sun, Hui-Lan (1); Yu, Hai-Yan (1); Wang, Bo (1); Tu, Gan-Feng (1) 2008, 29 (12):  1729-1733.  DOI: - Abstract ( 260 )   HTML   PDF (1429KB) ( 559 )   The properties of 12CaO·7Al2O3 obtained by ways of conventional leaching and enhanced ultrasonic leaching were studied under otherwise equal conditions. The results showed that the alumina leaching rate of Na2OC 80 g · L-1 under the action of ultrasonic wave is higher than that of Na2OC 120 g · L-1 by conventional ways and that the leaching rate at 69°C under the action of ultrasonic wave is higher than that at 78°C, by conventional ways. Better effect is obtained while the ultrasonic wave is acting longer within the range 0-60 min. The leaching rate of alumina increases firstly then comes to easiness while the power of ultrasonic wave changes from 40 to 140 W. Explores preliminarily mechanism of the function of ultrasonic wave, i. e. the ultrasonic radiation can speed up the moving velocity of ions to accelerate the mass transfer and break up the agglomeration of particles and, as a result, the leaching rate of alumina is improved. References | Related Articles | Metrics

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On the influencing factors on H3BO3 recrystallization Gong, Dian-Ting (1); Li, Feng-Hua (1); Fan, Zhan-Guo (1); Liu, Su-Lan (1) 2008, 29 (12):  1734-1737.  DOI: - Abstract ( 717 )   HTML   PDF (225KB) ( 3243 )   Discusses emphatically some influencing factors on the recrystallization of H3BO3, such as the solution concentration, crystallization temperature/time and stirring speed in the solution of H3BO3-H2O system. The rate of crystallization can be up to over 88% if the crystallization temperature/time is constant and the boric acid concentration is controlled within 28.5%~31.0%. And if the crystallization temperature is selected in the range of 5~10°C, the different cooling ways all effect slightly the crystallization rate of boric acid. But, if a quenching is implemented during high temperature with the temperature cooled to a certain extent and then cooled slowly, most of boric acid crystals are provided with a certain grain size. In our lab the proper crystallization time is about 15 h. If the boric acid solution concentration is 28.5%, and final crystallization temperature is 10°C that is held for 15 h, the slow stirring speed benefits the formation of boric acid crystals. References | Related Articles | Metrics

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Effect of iron reduction degree on leaching results of pre-reduced laterite ores with thin acid Chang, Yong-Feng (1); Zhai, Xiu-Jing (1); Fu, Yan (1); Zhang, Ting-An (1) 2008, 29 (12):  1738-1741.  DOI: - Abstract ( 492 )   HTML   PDF (267KB) ( 931 )   The Ni-bearing laterite ores were investigated experimentally by reducing roasting through microwave heating then leaching out in thin sulfuric acid. The effects of the amount of active carbon powder added in, microwave power and heating time on the reduction degree of iron oxide in the ores were tested, as well as the effect of iron oxide reduction degree on the leaching rates of nickel and iron. The results showed that the iron reduction degree in the ores increases with the added amount of active carbon powder, microwave power and heating time. For example, the reduction reaction process can be completed under 800 W for 12.5 min. The relationship between leaching rate of nickel and iron reduction degree is nearly linear, but the leaching rate of iron will rapidly increase if the iron reduction degree exceeds 60%. So, it is better to control the iron reduction degree to be 60%. Correspondingly, the leaching rate of nickel and iron is about 85% and not over 30%, respectively. References | Related Articles | Metrics

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Process mineralogy of low-grade double refractory gold ore and influencing factor on gold leaching Yang, Hong-Ying (1); Gong, En-Pu (2); Yang, Li (1) 2008, 29 (12):  1742-1745.  DOI: - Abstract ( 326 )   HTML   PDF (282KB) ( 1136 )   The samples used were from a gold mine in Yunnan Province, which are all of the typical of low-grade double refractory gold ore containing 2.4 g/t Au, 0.97 wt% As and 1.47 wt% C. The leaching rate of gold as a result of flotation concentrates and extraction by cyanidation is 10.43%, and it becomes 46.52% if the extraction process is roasting-cyanidation, which is thus referred to as extraordinary refractory gold ore in which the metallic minerals are mainly the pyrite and arsenopyrite and gangue minerals mainly cover the quartz, sericite, dolomite, calcite, illtie and clay mineral. Most of the occurrence state of gold in such a low-grade double refractory ore is invisible, i.e. mainly the inclusion gold or colloidal gold in sub-micro or super-micro state, the natural gold particles included in the pyrite and arsenopyrite crystals are the majority with electrum in minority. The influencing factors on low gold recovery are the inclusion gold, ore containing arsenic, carbonaceous matter and clay minerals. References | Related Articles | Metrics

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Experimental investigation on bio-leaching Cu-Ni ore tailings Yu, Juan (1); Yang, Hong-Ying (1); Tong, Lin-Lin (1); Chen, Sen (1) 2008, 29 (12):  1746-1749.  DOI: - Abstract ( 236 )   HTML   PDF (307KB) ( 704 )   The effects of pH value, mass fraction of pulp, ore particle size, inoculation concentration and dose of the surfactant Tween 20 on the bio-leaching rates of copper and nickel in Cu-Ni ore tailings were investigated through orthogonal test. The experimental results showed that the optimum conditions for copper extraction by bio-oxidation of Cu-Ni ore tailings are pH value 1.5, particle size less than 0.074 mm, inoculation concentration 50%, with no use of the surfactant Tween 20. And the optimum conditions for nickel extraction are pH value 1.0, particle size bigger than 0.147 mm, inoculation concentration 25%, with no use of the surfactant Tween 20. The copper and nickel leaching rates are thus up to 63.41% and 91.74%, respectively, after bio-oxidation. References | Related Articles | Metrics

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Composition and microstructure of biomedicine-oriented magnesium alloys Guan, Ren-Guo (1); Wang, Fu-Xing (1); Li, Jiang-Wei (1); Zhu, Li-Jie (1) 2008, 29 (12):  1750-1753.  DOI: - Abstract ( 231 )   HTML   PDF (480KB) ( 530 )   The effects of Ca and Mn on the microstructure of as-cast Mg alloy were investigated. Through the microstructure observation of Mg alloy ingot and SEM energy spectrum analysis. It is found that: the Mg-2.0Mn alloy is composed of a-Mg matrix and α-Mn point precipitates and Mg-0.5Ca alloy is composed of a-Mg matrix and Mg2Ca phase formed due to non-equilibrium solidification. Ca and Mn elements can provide grain refinement for the microstructure of Mg alloy. Finer microstructure can be obtained if Ca and Mn are added into the alloy simultaneously, with more homogenous and roundness grains and decreased amount of second-phase particles. The reasons are that the wettability of Mn is improved by Ca to enhance the dissolubility and diffusivity of Mn, and the decreasing temperature enables the Mn atoms to be precipitated continuously from the α-Mg matrix, thus providing lots of crystalline nucleus for alloy solidification. References | Related Articles | Metrics

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Reliability calculation model of a gear considering frequency of random loading actions Yue, Yu-Mei (1); Wang, Zheng (1); Xie, Li-Yang (1) 2008, 29 (12):  1754-1756+1786.  DOI: - Abstract ( 237 )   HTML   PDF (1357KB) ( 703 )   The effect of frequency of loading actions on the reliability of a gear is studied. With the conditional reliability introduced in and without the assumption that there is independent failure mode of gear, a reliability calculation model of gear with multiple failure modes is developed using the stress-strength interference model. According to the statistical meaning of random loading actions, the reliability model of a gear under frequent random loading actions is developed with the theory of order statistic. And the dependence of gear reliability on the frequency of loading actions is studied. The result shows that the gear reliability decreases with the increasing frequency of random loading actions even if no strength reduction. References | Related Articles | Metrics

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The method to determine the strength distribution and reliability computation for continuous system Hao, Guang-Bo (1); Xie, Li-Yang (1); Li, Li (1) 2008, 29 (12):  1757-1761.  DOI: - Abstract ( 238 )   HTML   PDF (280KB) ( 536 )   Because of lack of valid mathematical model to analyze the reliability of a continuous system such as pipeline, the continuous system is discredited to become a series system composed of a great number of virtual elements. A Weibull expression of the strength distribution of continuous system is deduced by minimal order statistic, then, the strength distribution is determined by parameter transform and able to be expressed by the parameters obtained from tests, and those parameters are evaluated using the maximum likelihood estimate. As a result, a reliability model of system level stress-strength interference is developed available to reflect the failure dependence among segments, and simulate the relationship between reliability and length of continuous system. It is shown that the reliability model developed can provide a basis for the reliability assessment of continuous systems of different sizes, and the reliability of a large-size continuous system is lower bounded. References | Related Articles | Metrics

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A combinational positioning kinematic algorithm for 3-RPS parallel robot in 2-DOF space Song, Wei-Gang (1); Ren, Jing (1); Zhu, Guan-Ya (1) 2008, 29 (12):  1762-1765.  DOI: - Abstract ( 329 )   HTML   PDF (376KB) ( 832 )   The 2-DOF space parallel mechanism can be applied to the working occasions that two components are under high acting force and accurate attitude is in need. The positioning-kinematics constraint equations are thus given for the 2-DOF and 3-RPS robot, with its forward and inverse kinematic algorithm discussed. The rod-length-search method for the forward solution of parallel robot position is improved. Combining with the quasi-Newton method to solve nonlinear equations, a combinational algorithm able to solve multi-solution to equation set with high computational accuracy is presented to deduce the inverse solving process of the position of 2-DOF and 3-RPS parallel robot. Exemplifications verify the algorithm's validity and how accurate it can provide. References | Related Articles | Metrics

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Architecture and technological study on virtual assembly system for prototypical products Yang, Jian-Yu (1); Zhu, Li-Da (1); Li, Hu (1); Wang, Wan-Shan (1) 2008, 29 (12):  1766-1769.  DOI: - Abstract ( 261 )   HTML   PDF (469KB) ( 566 )   Discusses the functional requirements for the prototype presentation, functional analyzing and virtual assembly of large-size or sophisticated products. A virtual reality system architecture was designed relevantly. Based on the idea of modularization, a system framework was proposed to be able to make the said system components work in either distributed or integrated way. The functions of main modules are discussed in detail, including the controlling core, assembly controlling module, graphic engine, file service module, data service module and application service module. Three of the key technologies, i. e. the initiative stereo display, assimilability evaluation and real-time collision detection are carefully studied. References | Related Articles | Metrics

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Analysis of dynamic elastic modulus of thin-wall cylindrical shells made from composites Li, Jian (1); Guo, Xing-Hui (1); Guo, Ming-Tao (1); Yan, Yun-Hui (2) 2008, 29 (12):  1770-1773.  DOI: - Abstract ( 258 )   HTML   PDF (432KB) ( 883 )   A method combining tests with theoretic analysis was presented to investigate the dynamic elastic modulus of the thin-wall cylindrical shells made from composites. Frequencies and modes of the thin-wall cylindrical shells made from glass-epoxy composite were obtained from tests of steady-state sinusoidal shock. FEM was applied to compute the dynamic flexural elastic modulus corresponding to the natural frequencies of different orders. With the results fitted, the Lorentzian relation between the frequency of shock-exciting force and dynamic elastic modulus was given. The results showed that the value of dynamic flexural elastic modulus is much less than that of the static one and decreases with the increasing frequency. The Lorentzian function is thus proved available to describe properly the relationship between dynamic flexural elastic modulus and vibrational frequency, and the theoretical value of the natural frequency calculated by the Donnell's shallow-shell theory coincides well with the testing results if applying the Lorentzian function to the calculation. References | Related Articles | Metrics

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Screening adsorbents for polycyclic aromatic hydrocarbons in plant oil used to treat contaminated soil and performance evaluations Gong, Zong-Qiang (1); Hu, Xiao-Min (1); Xu, Xin-Yang (1); Li, Pei-Jun (2) 2008, 29 (12):  1774-1777.  DOI: - Abstract ( 252 )   HTML   PDF (320KB) ( 780 )   To recycle the plant oil for remediation of the soil contaminated by polycyclic aromatic hydrocarbons (PAHs) which are contained in the oil, an adsorption process was employed to remove PAHs. Both column and batch adsorption experiments were conducted to screen the most suitable adsorbents from 10 possible ones via the evaluations of their physical and chemical properties. The results of dynamic absorbing column experiments showed that activated carbons F400 and F300 as adsorbents have the highest absorbabilities for PAHs from the plant oil, i. e. 55.39 μg ·g-1 and 23.82 μg · g-1, respectively. The fact reveals that the particle size of adsorbent has imported effect on PAH absorption, whereas the other adsorbents could hardly absorb PAHs from the plant oil. The results of batch adsorption experiments also showed the two kinds of activated carbons have the highest PAH absorbabilities, i.e. 211.85 μg·g-1 and 203.79 μg · g-1, respectively. References | Related Articles | Metrics

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Quantitative study on deterioration of mechanical properties of soilmass under chemical corrosion Cui, Qiang (1); Feng, Xia-Ting (1); Cheng, Chang-Bing (2); Yang, Cheng-Xiang (1) 2008, 29 (12):  1778-1781.  DOI: - Abstract ( 224 )   HTML   PDF (346KB) ( 628 )   A new quantitative method is presented to describe the deterioration of mechanical properties of soilmass under chemical corrosion. The aim is to analyze the chemical corrosion effect on the environment medium on the basis of chemical kinetics in combination with the microstructrual study on soilmass. Leaching tests were conducted and a conclusion was drawn that the change of unconfined compressive strength of clay taken from Guizhou is relevant to the goethite content of clay. Based on the analyses of electrical, magnetic and quantum chemical properties of minerals of clay, the type and numbers of cementation bonds between kaolin and goethite were determined. Analyzing kinetically of the chemical reaction between goethite and hydrochloride, the primary parameters, such as kinetic reaction rate order were obtained. Then, a mathematic model was developed to describe the time-dependent unconfined compressive strength of clay under chemical corrosion. And the numerical simulation results indicated that with the increasing corrosion time, the unconfined compressive strength of clay decreases then become stable finally. References | Related Articles | Metrics

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Study about culvert structure stress forecast based on AGA-BP system Fan, He (1); Ning, Bao-Kuan (2); Liu, Bin (1) 2008, 29 (12):  1782-1786.  DOI: - Abstract ( 232 )   HTML   PDF (337KB) ( 511 )   To solve the problem of neural network overtraining and blind network structure due to empirical formulae so as to forecast the stress in highly filled culvert better, an AGA-BP network system is developed via combining the advantages of GA and BP network together. By introducing the adaptive cross and mutative probability formula into the system to improve the conventional cross and mutative genetic operation, the local search ability is enhanced. Meanwhile, AGA fitness function is defined as the standard deviation of BP network's accumulation forecast errors and also one of genetic termination criteria. Taking the model test data as sample, the network architecture is determined by two methods, i.e. AGA-BP system and empirical formulae, to forecast the culvert stress. The results of both methods are compared with each other, and the AGA-BP system is verified more feasible and excellent in forecasting the highly filled culvert stress. References | Related Articles | Metrics

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Risk-oriented evaluation based on fuzzy proximity for clusters Gao, Fei (1); Li, Kai (1); Liu, Rui (2) 2008, 29 (12):  1787-1790+1802.  DOI: - Abstract ( 254 )   HTML   PDF (118KB) ( 500 )   Analyzing the causes of periodic, structural and network risks for mature clusters, a risk-oriented evaluation system including 21 indices is proposed. Then, the characteristic patterns of operation of a mature cluster at different risk levels are described. According to the complexity and uncertainty of cluster system, a TOPSIS (technique for order preference by similarity to ideal solution) comprehensive evaluation method in multi-object decision making theory is also proposed. The way the asymmetric proximity between the cluster's risk index system and actual operation conditions are calculated and, based on TOPSIS, the positive and negative ideal grades are determined. The proximities between each and every operation condition and ideal grades are thus compared to determine the risk level of mature cluster. An example is given to show the feasibility of the method. References | Related Articles | Metrics

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Analysis of human factor accidents in railway operation and countermeasures Guo, Fu (1); Hao, Jin-Quan (1); Liu, Chun-Hai (1) 2008, 29 (12):  1791-1794.  DOI: - Abstract ( 504 )   HTML   PDF (242KB) ( 1522 )   Based on the data of train operation accidents from 2001 to 2005 provided by a railway administration. The human errors were categorized into five types, i. e. omission, agent, disorder sequence and timing. By data processing statistically and data analysis, it was found that the main types of human error are the agent error and omission error. With correlation analysis made between human errors and their main causes, it was also found that the education, training and information communication especially the organizational management are the important factors of agent error, while the omission errors have relates to the operations and design factors especially the running procedures. The analysis of root causes of the human factor accident showed that the agent errors are mainly poor quality of basic operations, violation of regulations and reckless acts, while the omission errors are mainly because of carelessness and inefficient monitoring. To improve the current situation, some measures are suggested to take from three aspects: designing the man-machine system optimization, strengthening the control management and developing the human factor database. References | Related Articles | Metrics

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Fixed point theorems of increasing operator and its iterative solutions Sun, Tao (1); Wu, Li-Bing (1); Duan, Xiao-Dong (2) 2008, 29 (12):  1795-1798.  DOI: - Abstract ( 244 )   HTML   PDF (1827KB) ( 706 )   Let E be a Hilbert space, some new theorems of existence of fixed point of increasing operator are obtained in strongly measurable space Lp [I, E ], as well as the iterative solutions to increasing operator. Moreover, we get the conclusion that the conjugate space of Lp [I, E] is Lq [I, E] and, for application, the maximal and minimal solutions to a class of nonlinear integral equations in Hilbert spaces and relevant monotone iterative technique are studied. References | Related Articles | Metrics

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FEM study on stability of superconducting magnet withstanding over-current impulse Bai, Zhi-Ming (1); Wu, Chun-Li (2) 2008, 29 (12):  1799-1802.  DOI: - Abstract ( 264 )   HTML   PDF (373KB) ( 665 )   The quench behavior was simulated using the FEM software COSMOS 4.0 for a superconducting magnet which was wound by Bi2223/Ag tape was subjected to an over-current impulse. Programming the VB data analysis to discuss the simulation results, how the transverse and longitudinal temperature distributions change in the core of the magnet winding were known, thus giving the maximum temperature curves in the winding of superconducting magnet under different over-current impulses at 20 K as ambient temperature. Then, the allowable duration of an over-current impulse was taken as the criterion to judge the stability of a superconducting magnet withstanding over-current impulse, based on the local high temperature resulting from over-current impulse in relation to the minimum propagation current at the temperature. This will provide a significant reference for the study on the operating stability of high-temperature superconducting magnet. References | Related Articles | Metrics