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15 January 2012, Volume 33 Issue 1 Previous Issue    Next Issue
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Hybrid intelligent optimal control in flotation processes Li, Hai-Bo (1); Zheng, Xiu-Ping (1); Chai, Tian-You (1) 2012, 33 (1):  1-5.  DOI: - Abstract ( 570 )   HTML   PDF (2057KB) ( 904 )   In the flotation process, the concentrate grade and the tailing grade are crucial technical indices which reflect the product quality and efficiency. There are strong nonlinearity and uncertainties in such technical indices dynamic behavior s, which can hardly be described accurately with mathematical models. The technical indices which cannot be measured online continuously vary with boundary conditions. Therefore conventional control methods are incapable of keeping the actual concentrate grade and tailing grade within their target ranges. An intelligent control method comprised of a pre-setting model based on the case-based reasoning (CBR) method, a feedback compensator and a feed forward compensator based on the rule-based reasoning (RBR) method, and a soft sensors using RBF neural network was presented. The approach proposed has successfully been applied to the flotation process of a hematite ore processing plant, and its effectiveness is proved evidently. References | Related Articles | Metrics

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A modified receding horizon control for discrete linear zero-sum games Cao, Ning (1); Feng, De-Zhi (1) 2012, 33 (1):  6-9.  DOI: - Abstract ( 487 )   HTML   PDF (1495KB) ( 630 )   The zero-sum games of discrete linear time-invariant (LTI) systems using a modified receding horizon control scheme were investigated. Different from conventional RHC, the proposed scheme updates its terminal weighting matrix in performance index as the stage moves forward. This is equivalent to lengthening the horizon size. The control policies generated by the proposed algorithm converge to the solution of the infinite horizon zero-sum games. Furthermore, it ensures the uniform ultimate exponential stability of closed-loop system without imposing any constraints on the terminal state, the horizon size, or the terminal cost. Simulation shows the effectiveness of the proposed algorithm. References | Related Articles | Metrics

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A cross-layer congestion control algorithm for wireless sensor network Li, Ming-Wei (1); Jing, Yuan-Wei (2); Chen, Xiang-Yong (2) 2012, 33 (1):  10-12+20.  DOI: - Abstract ( 480 )   HTML   PDF (801KB) ( 696 )   A congestion control algorithm based on node-congestion and link-congestion was presented with sliding mode variable. Min-data package of node outgoing traffic was preferentially transmitted in the link-congestion; and active queue management method was used for the congestion control of the node level. The controller implements the purpose that congestion control can be simultaneously carried in MAC layer and transport layer. It can adaptively adjust the data sending rate according to the local congestion status of the network nodes, and the MAC channels are adaptively allocated. The validity of the proposed algorithm was proved by the Lyapunov function. Simulation results indicate that the algorithm restrains the congestion in the wireless sensor network, and reduces significantly the queuing time. References | Related Articles | Metrics

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An adaptive sliding mode output feedback control strategy for a class of uncertain discrete systems Huang, Feng-Zhi (1); Jing, Yuan-Wei (1) 2012, 33 (1):  13-16.  DOI: - Abstract ( 568 )   HTML   PDF (1657KB) ( 560 )   The problem of sliding mode output feedback control for uncertain discrete systems was investigated. The uncertainty of the discrete system was assumed to be mismatched, with an unknown norm bound. A dead-zone adaptive law was designed to identify the unknown bound online. The discrete sliding mode controller was designed based on the multirate output sampling theory. The discrete system is asymptotically stable with the proposed controller. Multirate output sampling is achieved by setting the output signals in a faster sample rate than that of the input signals, through relevant calculation, the current system states can be evaluated from the inputs at the previous time instance and the current outputs. Finally, a numerical example is provided to demonstrate the effectiveness of the proposed control strategy. References | Related Articles | Metrics

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Analysis of a SIRS model with nonlinear incidence rate on complex networks Cao, Yu (1); Jing, Yuan-Wei (1); Yuan, Feng (1); Shao, En-Xiang (1) 2012, 33 (1):  17-20.  DOI: - Abstract ( 539 )   HTML   PDF (1215KB) ( 815 )   An improved SIRS (susceptible-infected-removed-susceptible) model with nonlinear incidence rate was proposed according to the actual exposure of people. The conclusion that the existence of the threshold and how the threshold of this model is concerned with the topology of networks was deduced by the mean-field theory and the approach in Lyapunov stability theory; The diseases will extinguish when the system satisfied the threshold condition; The existence of threshold is proved by the hypothesis theory and the system must reach the trivial steady state under some conditions, which was another conclusion. The numerical simulation results indicated that the theoretical conclusions are valid, and the SIRS model with nonlinear incidence rate approaches the actual epidemic more accurately. References | Related Articles | Metrics

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Robust H∞ control for time-delay systems based on augmented Lyapunov functionals Li, Sheng-Tao (1); Jing, Yuan-Wei (1); Liu, Xiao-Mei (2) 2012, 33 (1):  21-24+34.  DOI: - Abstract ( 455 )   HTML   PDF (2186KB) ( 828 )   The problem of delay-dependent robust H∞ control for systems with state-delay was investigated. An improved delay-dependent bounded real lemma (BRL) was established in terms of linear matrix inequalities (LMIs) by using augmented Lyapunov functionals and free-weighting matrices method, ensuring the resultant closed-loop system asymptotically stable and a prescribed H∞ performance level. Based on the obtained BRL, the state feedback H∞ control law with memory was given in terms of the feasible solutions of LMIs. When the time-varying norm-bounded uncertainties appeared in a time-delay system, the explicit design approach of the robust H∞ controller was also given and formulated in the form of LMIs. Numerical examples are provided to demonstrate the reduced conservatism and validity of the proposed conditions. References | Related Articles | Metrics

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Guaranteed cost control for the singular networked control system with uncertain time-delay Wang, Jun-Yi (1); Li, Chun-Ji (2); Chen, Xiang-Yong (1) 2012, 33 (1):  25-29.  DOI: - Abstract ( 539 )   HTML   PDF (1109KB) ( 701 )   The problem of guaranteed cost control for the regular and impulse-free singular networked control system was studied. For the singular networked control system with clock-driven sensor, event-driven controller and actuator, and the uncertain time-delay not more than one sampling period, the sufficient condition of the existence of guaranteed cost control law for state feedback was derived through Lyapunov theory and linear matrix inequality, and the guaranteed cost control law design method for state feedback was also proposed. Finally, the state feedback guaranteed cost control law for singular networked control system with uncertain time-delay is demonstrated by a simulation example, thus the proposed approach is valid. References | Related Articles | Metrics

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Lightweight energy-efficient distributed target tracking algorithm in wireless sensor networks Zhang, Jian (1); Wu, Cheng-Dong (1); Chu, Hao (1); Dai, Yuan-Jun (1) 2012, 33 (1):  30-34.  DOI: - Abstract ( 540 )   HTML   PDF (1925KB) ( 541 )   An energy-efficient distributed multi-sensor collaborating target tracking algorithm was presented, which dealt with the problem of node scheduling and energy conservation for the uncertainties of complex motion tracking in the research of wireless sensor networks. According to the target state and the node density within the local monitoring region, the cluster size was determined by the residual energy and the history of node scheduling to balance the energy consumption. The Gaussian Cost-Reference particle filter was utilized to reduce the dependence on noise modeling in the target tracking process. Simulation results show that the algorithm can achieve the required tracking accuracy, and the node scheduling problem is solved to balance the energy consumption. References | Related Articles | Metrics

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Vein image feature extraction and matching based on regional shapes Xue, Ding-Yu (1); Jia, Xu (1); Cui, Jian-Jiang (1); Pan, Feng (1) 2012, 33 (1):  35-38+64.  DOI: - Abstract ( 517 )   HTML   PDF (1224KB) ( 773 )   In order to recognize one's identity accurately, an algorithm of feature extraction and matching based on regional shape was presented. The vein image was transformed into binary image through preprocessing first, the binary image was then thinned, and skeletal information of the vein image was obtained. Afterwards, the four connecting areas were labeled, then the endpoints and crossing points which are linked with the connecting area were found. The edge of the connecting area was approximated with several lines through the minimal distance method, and the angles of these lines were regarded as the feature of vein image. Finally, the local region was matched through the improved longest common subsequence method, and the global image was matched by the improved Hausdorff distance method. The experimental result shows that the acquired image feature by this algorithm has stronger distinguishing, the recognition result is affected less because of information missing in collecting vein images, and the correct recognition rate exceeds 96%. References | Related Articles | Metrics

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A multi-orientation Gabor filter and Adaboost based iris recognition method Zhang, Xiang-De (1); Li, Ming-Qi (1); Wang, Qi (1); Sun, Yan-Rui (1) 2012, 33 (1):  39-42.  DOI: - Abstract ( 484 )   HTML   PDF (1496KB) ( 762 )   A new method for iris feature extraction and recognition was proposed based on the global and local texture information of iris. The normalized iris was divided first. Then the multi-orientation Gabor filters were used to encode the whole iris and sub-block iris, and the feature vector was constructed. Furthermore, the Adaboost algorithm was adopted to choose some features whose recognition performances are good. The results of the experiments carried out on CASIA-IrisV3-Lamp database indicate that the accuracy of recognition reaches up to 99.85%. Moreover, the algorithm has good recognition performance on the NICE: II database which contains a large amount of poor quality images. It shows that the method not only can take fully advantage of the texture information of iris, but also can reduce efficiently the effect of noises. References | Related Articles | Metrics

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Gait recognition based on sparse representation Yang, Qi (1); Xue, Ding-Yu (1); Cui, Jian-Jiang (1) 2012, 33 (1):  43-46.  DOI: - Abstract ( 552 )   HTML   PDF (862KB) ( 787 )   A method based on sparse representation for gait recognition was proposed using the CASIA_B and CUSD database. The gait silhouette was centralized and normalized first, then the AEI (active energy image) was calculated based on the previous operation and used as the feature image for gait recognition. Two methods were used to establish the dictionary and calculate the decomposition coefficients for the sparse representation: one for reconstruction, and the other for discrimination. OMP (orthogonal matching pursuit) algorithm was used for coefficients decomposition. The result of experiment shows that the proposed method can effectively recognize the gait, and the accuracy of the recognition is high and recognizing speed is much faster. References | Related Articles | Metrics

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The application of harmony search algorithm in clustering analysis Yi, Yu-Feng (1); Gao, Li-Qun (1); Guo, Li (2) 2012, 33 (1):  47-51.  DOI: - Abstract ( 617 )   HTML   PDF (1195KB) ( 578 )   An improved harmony search algorithm (IHS) was proposed and used in clustering analysis. The feedback mechanism was introduced first into the harmony search algorithm, and harmony memory considering rate and bandwidth can be dynamically adjusted by calculating the difference between the best harmony and the worst harmony, which makes the IHS converge to the global optimal solution quickly. The proposed algorithm updates the decision variables which represent the cluster centers to minimize the value of objective function and get the best partition of data samples. A method which can automatically determine the true number of clusters of data samples was then proposed, the true number of clusters was calculated when the input number of cluster center is greater than the true number of clusters. Finally, four performance measures were used to compare the proposed algorithm with ANT-based and traditional harmony search (HS) based clustering analysis algorithms, it is shown that the performance of the proposed algorithm is better than the other two algorithms. References | Related Articles | Metrics

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PBIL and maximum-flow based algorithm of charge design problem Zhu, Jun (1); Jia, Shu-Jin (2); Du, Bin (1); Liu, Shi-Xin (1) 2012, 33 (1):  52-55.  DOI: - Abstract ( 502 )   HTML   PDF (767KB) ( 562 )   A mathematical model and an optimization algorithm, which is based on PBIL (population-based incremental learning) and network maximum flow, were proposed for the charge design problem of steel-making. The algorithm first finds an upper bound of the number of charges, which serves as the baseline for designing PBIL with 0-1 chromosome encoding, through a heuristic rule. Each chromosome represents a selection scheme of charges, and the network maximum flow theory is used to calculate the fitness value for chromosome. The optimal order-furnace matching strategy could be obtained after several iterations. Simulations on real production data indicated that the proposed algorithm can obtain an optimized matching solution within reasonable time, and can provide enough decision support for planners. References | Related Articles | Metrics

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Scatter search for solving multi-objective disassembly sequence optimization problems Guo, Xi-Wang (1); Liu, Shi-Xin (1); Wang, Da-Zhi (1) 2012, 33 (1):  56-59.  DOI: - Abstract ( 500 )   HTML   PDF (760KB) ( 741 )   To solve disassembly sequence optimization problems, a multi-objective mathematical model was established with optimization objectives of minimizing the disassembly time and maximizing the disassembly profit. The linear weighted method was used to transform the multi-objective model into single objective one, and an improved scatter search algorithm was presented. In the algorithm, the PPX procedure was used as a subset combination operator, and the local search disassembly sequencing operator was used to improve new solutions generated by the combination operator. The effectiveness of proposed model and algorithm for multi-objective disassembly sequence optimization problems are validated by the testing results. References | Related Articles | Metrics

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Evolutionary game analysis based on the problem of cadres movement Zhang, Xue-Feng (1); Fan, Kai (1); Li, Guang-Yang (1); Wang, Hao (2) 2012, 33 (1):  60-64.  DOI: - Abstract ( 398 )   HTML   PDF (965KB) ( 613 )   In order to improve the efficiency of the leadership and bring up unit culture, a decision making model and a payoff matrix were established for the current leadership and the previous leadership. A replicator dynamic equation was used to analyze the evolution of previous work styles. According to local stability of Jacobi matrix, the possible stable states of evolution were analyzed under the circumstances that the different incomes of different strategies meet the distinct relationships. The analysis results show that the evolution direction in the system is related to the reward and penalty parameters in the payoff matrix. The proposed model provides a theoretical reference to enforce scientific management for organizational departments. References | Related Articles | Metrics

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Design and implementation of a multi-core embedded gateway for linking WSN and internet Zhao, Hai (1); Shao, Shi-Liang (1); Zhu, Jian (1); Zhang, Kuan (1) 2012, 33 (1):  65-68.  DOI: - Abstract ( 469 )   HTML   PDF (1304KB) ( 921 )   Focusing on the bandwidth limitation of transmission between Internet and WSN (wireless sensor network), a multi-core embedded gateway was designed. The gateway was designed using dual-ported memory CY7C026 as the public memory block, ATmega128(L) as the processor module, RTL8019AS as the full-duplex Internet controller, and CC2420 RF chip as the wireless communication module. Nut/OS was utilized to reduce network protocol. Using multiple chips for parallel processing, seamless link could be enforced between Internet and WSN. The experimental results show that the system can provide high stability and improve the transmission bandwidth. References | Related Articles | Metrics

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A route optimization scheme for mobile network based on improved HMIPv6 Gao, Tian-Han (1); Guo, Nan (2) 2012, 33 (1):  69-72.  DOI: - Abstract ( 446 )   HTML   PDF (913KB) ( 558 )   Taking the NBS (NEMO basic support) protocol mobile network as the research subject, a route optimization scheme based on improved HMIPv6 mobile network was proposed to solve mobility management and route optimization problems. HMIPv6 and NBS were integrated to construct hierarchical mobile network architecture. Utilizing the regional mobility management mechanism, the registration costs of mobile nodes are reduced. Moreover, a novel route optimization scheme was also introduced through improving HMIPv6 to eliminate pinball routing of mobile network node. The analytical results show that the proposed scheme outperforms NBS in both additional packet overhead and mobility management overhead. References | Related Articles | Metrics

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Distributed authenticated skip list for secure P2P storage Xu, Jian (1); Zhou, Fu-Cai (1); Li, Xin-Yang (2); Zhu, Zhi-Liang (1) 2012, 33 (1):  73-76.  DOI: - Abstract ( 502 )   HTML   PDF (517KB) ( 749 )   Aiming at the problem of data authenticated in P2P storage environments, a distributed authenticated skip list (DASL) based on Goodrich's method was proposed. The path-searching algorithm, object authentication algorithm as well as object insertion/deletion algorithm based on the distributed object location algorithm were also presented. The analysis of DASL cost was given and the employed probability theory and statistical analysis were compared. Such analysis show that the DASL scheme is more efficient than sign-all scheme. The implementation of the DASL does not rely on the location algorithm, which makes it simple, expandable, and feasible. Therefore, the DASL can be easily applied to the existing P2P storage system and fulfills the data authentication requirements. References | Related Articles | Metrics

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Effect of strain of Co-W thin film on effective magnetic anisotropy energy Qin, Gao-Wu (1); Xiao, Na (2); Li, Song (1); Ren, Yu-Ping (1) 2012, 33 (1):  77-80+85.  DOI: - Abstract ( 483 )   HTML   PDF (1577KB) ( 655 )   Co-11at%W films with different thicknesses (9~80 nm) were deposited on MgO (220) single crystal substrate with Cr underlayer (100 nm) by magnetron sputtering. The epitaxial growth relationship between Cr and Co-W layer is Cr(112)[111¯]//Co-W(101¯0)[1¯21¯0] and Cr(112)[11¯0]//Co-W(101¯0)[0001]. With the increasing of Co-W film thickness, the in-plane strain of Co-W layer decreases from-0.388?4% to -0.2711%, while the out-of-plane strain decreases from 0.7813% to 0.5445%, and the first order effective magnetic anisotropy constant K1eff decreases from 3.82×106 erg/cc to 2.58×106 erg/cc correspondingly. The results showed that the effective magnetic anisotropy energy of magnetic layer can be tuned by adjusting the strain between underlayer and magnetic layer. References | Related Articles | Metrics

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Microstructure and mechanical properties of high heat input welding steel Zhang, Peng-Yan (1); Gao, Cai-Ru (1); Zhu, Fu-Xian (1) 2012, 33 (1):  81-85.  DOI: - Abstract ( 560 )   HTML   PDF (2563KB) ( 568 )   In order to study high heat input welding steels for industrial production processes, a high heat input welding steel for crude oil storage tank was developed in domestic steelworks by titanium nitride and oxide refinement dispersion technology. The process and condition of alloying addition were controlled. The impact toughness of a traditional steel and the trial steel was compared after welding thermal simulation and vertical position gas-electric welding. The effects of density, type and size of inclusion on heat affected zone were analyzed. The results showed that the mechanical properties of this steel meet the demand of national standard, and the yield ratio is below 0.9. The microstructure of fusion line with a heat input of 400 kJ/cm consists of proeutectoid polygonal ferrites and numerous acicular ferrites, therefore the welded joints have excellent low temperature toughness. TiOx-Al2O3-MnS complex inclusions with the size of 1~3 μm are the most favorable sites for the nucleation of IAF (intragranular acicular ferrites). References | Related Articles | Metrics

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Online simulation and application of welding heat cycle Feng, Ying-Ying (1); Luo, Zong-An (1); Zhang, Dian-Hua (1); Su, Hai-Long (1) 2012, 33 (1):  86-89.  DOI: - Abstract ( 502 )   HTML   PDF (1578KB) ( 593 )   A software for welding heat cycle simulation was developed based on the Windows XP system. The software was programmed by LabVIEW 8.2 and STEP 7 and was embedded in the MMS series thermo-mechanical simulator which developed by State Key Laboratory of Rolling and Automation, Northeastern University. The results showed that the online simulation of welding heat cycle process can be achieved by the software, which can reflect and describe quantitatively the main influencing factors of heat cycle and the correlation among them. Through the acquisition of welding heat cycle curve and the analysis of the sample morphology, the experimental study of heat affected zone affected by the peak temperature, etc. can be completed, and the application of online simulation of welding heat cycle process can be realized. References | Related Articles | Metrics

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Comparative study of desulphurization with powder injected into hot iron through lance and slot porous plug Zhou, Jian-An (1); Sun, Zhong-Qiang (2); Zhan, Dong-Ping (1); Liu, Chun-Ming (1) 2012, 33 (1):  90-93.  DOI: - Abstract ( 574 )   HTML   PDF (991KB) ( 716 )   A comparative experimental study on desulphurization of hot iron with nickel by injecting powder through slot porous plug fixed at the bottom of ladle and a usual overhead injecting technology was carried out in an industrial 20 tones ladle. The results showed that when the consumption of calcium carbide powder is 4 kg/t, the desulphurization ratio of the bottom powder injection is 81%~90%, and the heat loss is 23~36°C; the desulphurization ratio of overhead powder injection is 59%~73% and the heat loss is 45~70°C. Although the difference of injecting time between them can be neglected, the total processing time of bottom injection technology is 5 min shorter than that of top injection technology. Therefore, compared with the other desulphurization technologies, the technology of injecting powder with the bottom position has a number of advantages, such as, the higher desulphurization efficiency, the less heat loss and the short recycle time. References | Related Articles | Metrics

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Effects of reducing atmosphere and gangue composition on reduction swelling of oxidized pellets Wang, Zhao-Cai (1); Chu, Man-Sheng (1); Tang, Jue (1); Xue, Xiang-Xin (1) 2012, 33 (1):  94-97+102.  DOI: - Abstract ( 561 )   HTML   PDF (1622KB) ( 836 )   The oxidized pellets were prepared with Fe2O3 and additional SiO2, CaO and MgO separately. The influences of two reducing atmospheres, including H2 and CO and gangue composition on pellets' reduction swelling were investigated. The results showed that the increasing of H2 in reducing atmosphere is good for lowering the reduction swelling, which ensures the intact grain structure and good quality of pellets. Meanwhile by adding a little CaO in Fe2O3 pellets, some liquid phases are generated in sintering and the metallurgical properties of pellets are improved. However, the amount of CaO should be controlled. Guaranteeing the product quality, slag connection can be obtained in sintering by controlling the TFe of pellets properly and adding some gangue, which lead to the improved strength and reduced reduction swelling. In addition, the properties of the pellets containing some MgO are improved due to the formation of a stable crystal structure. References | Related Articles | Metrics

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Study on forced cooling problem of high temperature balk cargo Chen, Wen-Zhong (1); Liao, Bai-Feng (1); Shi, Xue-Min (1); Liu, Hui (1) 2012, 33 (1):  98-102.  DOI: - Abstract ( 536 )   HTML   PDF (1656KB) ( 569 )   The temperature of balk cargo graphite produced by continuous graphitizing furnace was approximately 2600°C. Experiments were limited by the high temperature. In order to study the forced cooling situation of high temperature balk cargo, the numerical simulation was conducted on the optimized cooling unit by using the software Fluent. The temperature distributions of the cooling process for graphite were obtained. The results showed that the inlet temperature of the cooling unit is very high. To protect the cooling unit, heat-resisting materials are required. The outlet temperature falls to 324?K, which is much lower than the requirement. The cooling effect is remarkable. Both of the outlet temperatures of the water in two stage cooling units meet the requirements. There are in good agreement between the simulation results and the measurements. According to the simulation results, the cooling effect is tested and the further optimization for the optimized cooling unit is guided. References | Related Articles | Metrics

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Finite element analysis for dynamic characteristic of deep-groove ball bearing operating from acceleration to constant speed Zhang, Yu (1); Xie, Li-Yang (1); Wu, Ning-Xiang (1); Lu, Bing-Wu (2) 2012, 33 (1):  103-107.  DOI: - Abstract ( 564 )   HTML   PDF (1880KB) ( 645 )   A 3D finite element model for dynamic contact problem of deep-groove ball bearing was established. Considering the deformation of bearing components and actual loaded forms, the explicit dynamics solver LSDYNA was adopted to calculate dynamics response of bearing which operate from acceleration to constant speed and was subjected to three kinds of radial load. The result shows that the bearing experienced strong vibration in acceleration phase which extends to the beginning of constant speed. The equivalent stress was much higher than the yield strength of bearing steel regardless of radial load. With the increase of running time of constant speed of the bearing, the vibration was weaken obviously and the bearing entered a stable working status. The fluctuant range of the radial displacement of the shaft is smaller and the distance between bearing axis and the shaft center is farther when the radial load is higher. The shear stress parallel to rolling direction appeared asymmetrically in rolling element due to the simultaneous existence of pressure and friction force. References | Related Articles | Metrics

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Experimental study on the best testing parameters in eddy current testing method for small crack of steel bar Sun, Hong-Chun (1); Xia, Yong-Fa (1); Cui, Yu (1) 2012, 33 (1):  108-110+115.  DOI: - Abstract ( 445 )   HTML   PDF (1197KB) ( 631 )   In order to improve the accuracy of eddy current testing of steel bar with small cracks and reduce the nonlinear error due to select inappropriate testing parameters, 25# steel bars with 0.1 mm crack depth were detected by using the eddy current detector and the external probe under different frequency and lift-off value based on experimental model, and then the phase information was obtained. The influences of working frequency and lift-off value on the phase signals were studied for the eddy current testing. According to the minimum principle for the average standard deviation of linear fit, the best linear section was achieved between the detection parameters of the eddy current testing signal and phase parameter, which raises the detection accuracy of the bar with small cracks, and has important guiding role for choosing the eddy current testing parameters of external bars. References | Related Articles | Metrics

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Research on theoretical modeling of 3D chip of orthogonal turn-milling Zhu, Li-Da (1); Li, Hu (1); Yang, Jian-Yu (1); Wang, Wan-Shan (1) 2012, 33 (1):  111-115.  DOI: - Abstract ( 375 )   HTML   PDF (1984KB) ( 542 )   Aiming at the problems of varying chip thickness and depth due to the complex motion in orthogonal turn-milling, the mathematical models of centric and eccentric chip formation were proposed based on the orthogonal turn-milling theory, respectively. Consequently, the mathematical expressions of chip depth and thickness for both the circumference edge and the face edge were obtained. The theoretical model of orthogonal turn-milling chip was validated by comparing the geometric chip formation with the experimental one under the same cutting condition. The chip model may provide a theoretical foundation and reference for the research on orthogonal turn-milling mechanisms. References | Related Articles | Metrics

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Numerical simulation of gas drainage with high-position boreholes along coal seam Wang, Qing-Yuan (1); Yang, Tian-Hong (1); Chen, Shi-Kuo (1); Li, Tie-Liang (2) 2012, 33 (1):  116-119.  DOI: - Abstract ( 426 )   HTML   PDF (1327KB) ( 684 )   In the coal seam 19 of Baliancheng Coal Mine, the 62.1%~71.6% of gas emission was from goaf. A gas drainage procedure with high-position boreholes along seam in goaf was proposed in order to control the gas disaster. Based on the key stratum theory and the "O" shape circle theory, fissure pattern in the overburden rock strata above the goaf was analyzed. Through the study of the gas migration in overburden rock fissure, it is regarded that the gas flow follows the Darcy's law. A numerical simulation was done with the commercial software COMSOL-Multiphysics for gas drainage. It clearly illustrated the gas migration during the flow drainage. The results showed that the gas drainage reduces the gas pressure effectively. This study may provide theoretical basis for site gas drainage and is of important practical significance. References | Related Articles | Metrics

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Optimization of caving space for different angles of end-wall during pillarless sublevel caving Xu, Shuai (1); An, Long (1); Li, Yuan-Hui (1); Dai, Xing-Hang (1) 2012, 33 (1):  120-123.  DOI: - Abstract ( 580 )   HTML   PDF (1605KB) ( 580 )   Based on the principle for optimizing the caving space, the optimal index in line with "the maximum difference between the recovery ratio and dilution ratio" was determined, and the shape of ore-rock mass drawn down with these structural parameters was measured using side drawing approach. According to the shape parameters of ore-rock mass drawn down, together with the analogy method among similar mines and the empirical method, it was determined that the optimal caving spaces range from 3.6 m to 4.8 m. Besides, it was suggested that the end-wall leaning forward may be helpful in decreasing the dilution ratio and reducing the mixed waste rock. In accordance with the practice of foreign operating mines, the similar experiments of drawing space under the similarity ratio of 1:50 were conducted, and it was determined that the optimal drawing spaces are 3.6, 4.0, 4.4 and 4.8 m at the end-wall angles of 80°, 85°, 90°, respectively. The experimental results indicate that the optimal caving space for Meishan Mine is 4.4 m and the end-wall angle is 90° when the structural parameters are 18 m×20 m. References | Related Articles | Metrics

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Product characteristics of vanadium-titanium magnetite from Panxi by high pressure grinding roller Yuan, Zhi-Tao (1); Guo, Xiao-Fei (1); Yan, Yang (1); Han, Yue-Xin (1) 2012, 33 (1):  124-127+132.  DOI: - Abstract ( 519 )   HTML   PDF (2034KB) ( 759 )   Vanadium-titanium magnetite from Panxi was superfinely crushed by high pressure grinding roller. The particle size characteristics of the crushed product from different crushing processes were analyzed, and the modification of the work index of ball mill and emerging of the micro-crack by different crushing manner were studied. The results showed that, in crushed products, the reduction ratio increases and the size distribution becomes more uniform with increasing of the pressure on roller surfaces. The particle size decreases but uniformity reduces with increasing of the edge products circulating mass. And the fine fraction content of crushing products from -3.2 mm classification closed-circuit by HPGR increases obviously compared with that by Jaw Crusher and particle size distribution is more uniform. Large amount of intracrystalline cracks and cleavage cracks are generated in vanadium-titanium magnetite crushed by HPGR, which makes the Bond work index of ball mill (objective particle size is 0.074 mm) of vanadium-titanium magnetite 14.05% lower than that by Jaw Crusher. References | Related Articles | Metrics

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Wet pre-concentration of comminuted products by high-pressure grinding roller for lean hematite Liu, Lei (1); Yuan, Zhi-Tao (1); Han, Yue-Xin (1); Lü, Xue-Fang (1) 2012, 33 (1):  128-132.  DOI: - Abstract ( 519 )   HTML   PDF (2149KB) ( 598 )   The pre-concentration of comminuted products by high-pressure grinding roller for lean hematite was studied, using the cylindrical ferromagnetic medium. The effects of various factors including rod diameter, rod gap and background magnetic field intensity (BMFI), on indexes of pre-concentration were emphatically investigated and the force analysis of single mineral particles with different diameters in the separation zone was done. The results showed that as rod gap decreased, rod diameter and BMFI increased, the tailings grade and the tailings yield are reduced, but the Fe recovery is increased. Under the same BMFI, the magnetic capturing force increases on the coarse particles and decreases on the fine particles with the rod diameter increasing. For the actual locked particles, considering the gravity and viscous resistance of particles, the increase of rod diameter is beneficial for the capture of coarse particles but has no influence on the capture of fine particles, while the decrease of rod diameter is good for the capture of fine particles but bad for the capture of coarse particles of lean intergrowth. References | Related Articles | Metrics

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Evaluation on deep reduction of iron ore based on digital image processing techniques Gao, Peng (1); Han, Yue-Xin (1); Li, Yan-Jun (1); Sun, Yong-Sheng (1) 2012, 33 (1):  133-136.  DOI: - Abstract ( 510 )   HTML   PDF (1576KB) ( 698 )   The deep reduction of iron oxides and the growth of iron particles were conducted during reduction for refractory iron ore. Currently, metallization rate as an evaluation index of reduction can only evaluate reductive degree, but not particle size characteristics of iron particles. For building intact evaluation system of reduction, digital processing technology was used to analyze features of iron particles. Furthermore, formula for calculating the cumulative granularity property curve of iron particles was derived by utilizing the two-dimensional characteristic parameters, which collected and handled from digital images of material after reduction in combination with the spherical feature of iron particles, with which the size characteristics of iron particles under different conditions could be evaluated effectively. The experimental results showed that the separating index of iron powder products follows the changing tendency of iron particle size precisely. Consequently, evaluation method for the deep reduction of iron ore with digital image processing techniques is feasible. References | Related Articles | Metrics

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Deep reduction tests of antelope iron ore in Linjiang area Li, Yan-Jun (1); Han, Yue-Xin (1); Zhu, Yi-Min (1); Liu, Jie (1) 2012, 33 (1):  137-140.  DOI: - Abstract ( 527 )   HTML   PDF (1438KB) ( 549 )   Deep reduction single factor condition tests on antelope iron ore with the grade of 34.79% from Linjiang area in Jilin Province were conducted, and effect of the factors such as reduction temperature, reduction time and thickness of feed layer on deep reduction and magnetic separation result was investigated. The results indicated that reduction process is considerably influenced by reduction temperature and reduction time. Optimal conditions are as follow: reduction temperature 1275°C, reduction time 50 min, thickness of feed layer 30 mm, excess coal blending multiples 2.0, reduction coal particle size -1.5 mm, and ore particle size size -2.0 mm. Under these conditions, final product with content of Fe 93.05%, recovery 85% and metallization rate 91.29% is obtained, which meets the H92 standard requirement of direct reduction iron product of steelmaking field in China. References | Related Articles | Metrics

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Optimal stock replenishment model of perishable merchandise based on stochastic replenishment intervals and nonlinear deteriorating rate Zhang, Chuan (1); Liu, Bao-Zheng (2); Ji, Shou-Feng (1); Zhang, Cui-Hua (1) 2012, 33 (1):  141-144.  DOI: - Abstract ( 605 )   HTML   PDF (1602KB) ( 738 )   A set of multi-cycle stock replenishment strategies of perishable merchandise with price-varying demands was researched. The deteriorating rate is a nonlinear time-varying function and the replenishment interval is a random variable, whose density function is evenly distributed at intervals. An optimal replenishment model with replenishment level as the decision-making variable was constructed. Matlab was utilized to seek the extremum optimization solution. An example was given and sensitivity of the replenishment intervals was analyzed. The example showed that because goods tend to deteriorate, stock-out often occurs. In order to avoid this from happening, the replenishment intervals can be shortened to reduce commodity vacancy periods. In sum, this model provides a decision-making method for goods delivery of distribution centers and stock replenishment of supermarkets. References | Related Articles | Metrics

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An equilibrium analysis of competition between two-sided platforms with agent multi-homing Liu, Da-Wei (1); Li, Kai (1) 2012, 33 (1):  145-148.  DOI: - Abstract ( 839 )   HTML   PDF (507KB) ( 1959 )   In order to analyze the equilibrium conditions of competition between two-sided platforms with agent multi-homing, a baseline model with two-sided network effects was constructed, and by changing the model's assumptions, the conditions under three cases were discussed, including two-sided single-homing, one side multi-homing and partial multi-homing. Based on the studies of equilibrium price and market share under the three cases, it is found that multi-homing has a direct effect on the platforms' pricing strategies, and the platform tends to charge multi-homing agents and provide discounts for single-homing agents. The agent multi-homing not only influences the equilibrium conditions but also results in the tilt prices in two-sided markets. References | Related Articles | Metrics

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Superconvergence of the discontinuous finite element method for solving first-order hyperbolic problems Zhang, Tie (1); Li, Zheng (1) 2012, 33 (1):  149-152.  DOI: - Abstract ( 448 )   HTML   PDF (2095KB) ( 633 )   The discontinuous finite element method for solving the first-order hyperbolic problems was studied and the stability and convergence of this method were analyzed. For the k-order discontinuous finite elements, the negative norm error estimates are established on the solution domain and some suitably chosen subdomains by using the dual argument technique. Further, based on the negative norm error estimates, the O(h2k+1/2)-order superconvergence is shown for the error on average on these domains and their outflow faces. These theoretical results are verified by numerical experiments. References | Related Articles | Metrics