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15 February 2012, Volume 33 Issue 2 Previous Issue    Next Issue
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A sufficient condition for hyperstability of switched systems Wang, Xia (1); Tang, Yu-Jun (2); Zhao, Jun (1) 2012, 33 (2):  153-156.  DOI: - Abstract ( 440 )   HTML   PDF (324KB) ( 580 )   The hyperstability property of switched systems was investigated. The imported energy of each subsystem is from the input of the switched system or from the other subsystems. The whole imported energy of each subsystem was restricted by the Popov inequality with modified integral interval. Under the conditions that all the subsystems have finite imported energy, the hyperstability and asymptotical hyperstability of switched systems were studied on the basis of the dissipative theory of switched systems. According to the positive real lemma and Kalman-Yakubovich-Popov lemma, sufficient conditions were given which made the switched system have hyperstability and asymptotical hyperstability when switching signals were slow. Simulation results verified the conclusion. References | Related Articles | Metrics

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Maximization of network lifetime in data gathering systems Wang, Yan (1); Jing, Yuan-Wei (1) 2012, 33 (2):  157-160.  DOI: - Abstract ( 618 )   HTML   PDF (831KB) ( 597 )   To avoid network holes which are easy to form in a wireless sensor network, an energy efficient algorithm based on load balancing is proposed for a data gathering system. In the algorithm, the network is firstly divided into many concentric rings, and then the number of nodes in each ring is determined in terms of balancing energy consumption between the rings. Finally, an energy-balanced routing algorithm is proposed to achieve intra-ring load balancing. Simulation results show that the proposed algorithm has longer network lifetime and outperforms the existing energy-balanced data gathering (EBDG) and non-uniform deployment energy balance (NDEB) algorithms. Since the algorithm can balance the overall energy consumption, it is robust to the number of nodes. References | Related Articles | Metrics

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Robust fault-tolerant control for uncertain linear discrete systems with time-delay Yang, Dong-Mei (1); Sun, Jun-Na (1) 2012, 33 (2):  161-164.  DOI: - Abstract ( 488 )   HTML   PDF (485KB) ( 678 )   The paper focuses on the problem of robust fault-tolerant control based on the state feedback for a class of linear discrete systems with uncertain time-delay against the actuator failures, where the uncertainties of the parameters are norm bounded. Based on Lyapunov stability theory and LMI approach, a state feedback controller with memory is designed, which ensures that the closed-loop systems are asymptotically stable in all possible actuator failures cases. An LMI sufficient condition such that the systems possess integrity against the actuator failures is given. All the parameters of the controller can be obtained using the LMI toolbox in MATLAB. The simulation results demonstrate the feasibility and effectiveness of the proposed method. References | Related Articles | Metrics

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Coverage optimization of wireless sensor networks based on mobile nodes Huang, Yue (1); Wu, Cheng-Dong (1); Zhang, Yun-Zhou (1); Si, Peng-Ju (1) 2012, 33 (2):  165-168.  DOI: - Abstract ( 670 )   HTML   PDF (1064KB) ( 810 )   To improve the coverage rate of wireless sensor networks (WSNs) monitoring some regions, coverage optimization is studied for WSNs where nodes are randomly deployed. A probabilistic detection model considering false alarm rate, which is more practical, is applied to a mixed WSN with mobile nodes. A regional coverage rate is used to evaluate network coverage effect. Coverage holes are determined by calculating the joint detection probabilities of nodes, and a mobile nodes' optimization strategy based on the best probability is proposed. Simulation results show that the method proposed can find out coverage holes effectively and repair them by moving mobile nodes in smaller distances, thus improving the network coverage rate. References | Related Articles | Metrics

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Optimal modeling in SR-EAF power supply curves Feng, Lin (1); Mao, Zhi-Zhong (1); Yuan, Ping (1) 2012, 33 (2):  169-172.  DOI: - Abstract ( 461 )   HTML   PDF (442KB) ( 736 )   Analyzing the electric characteristics of a supplemental reactor electric arc furnace(SR-EAF) and comprehensively considering the influencing factors on production cost, we developed an optimized power supply model, where the multiple objects aiming at shortening smelting time, reducing electric power consumption per ton of steel, decreasing electrode consumption and prolonging lining life were employed in optimization. The effects of current on electrodes and linings and effects of a supplemental reactor and the output voltage of a transformer on power supply strategy were taken into account in this model, with such parameters optimized as the current of electric arc, the values of a supplemental reactor and service voltage. A new power supply strategy based on the optimized parameters was proposed and applied in actual production, which increased power supply efficiencies and economic benefits. References | Related Articles | Metrics

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Online detection of outliers of control process data Liu, Fang (1); Mao, Zhi-Zhong (1) 2012, 33 (2):  173-177.  DOI: - Abstract ( 609 )   HTML   PDF (779KB) ( 699 )   A new method for detecting the outliers of control process data is proposed to compensate the deficiencies of the conventional wavelet methods. A wavelet method is used to decompose the fitting error of the output and its estimate, and a RBF model with backfeed structure is developed to reduce the effect of the outliers on the precision of the RBF network, thus improving the robustness of the network. HMM is introduced into the analysis of the wavelet coefficents, which can recognize the outliers without presetting the detection threshold. Experiment and application show the validity of the proposed method. References | Related Articles | Metrics

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A FCM clustering algorithm based on global spatial similarity Yi, Yu-Feng (1); Gao, Li-Qun (1); Guo, Li (3) 2012, 33 (2):  178-181.  DOI: - Abstract ( 492 )   HTML   PDF (865KB) ( 768 )   The data in a class are discrete in spatial distribution when segmenting images using a conventional FCM clustering algorithm. For better results of image segmentation, an improved FCM clustering algorithm is proposed. In this algorithm, a global spatial similarity and a global intensity similarity between the pixels of an image and a cluster center are separately calculated and the proportion of the spatial feature to the intensity feature is adjusted according to the requirements, which enhances the continuity of the segmentation results in spatial distribution. Simulation results show the better segmentation accuracy obtained by the proposed algorithm, compared with the conventional FCM clustering algorithm. References | Related Articles | Metrics

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An improved differential evolution algorithm for reliability problems Li, Ruo-Ping (1); Feng, Da (2); Ouyang, Hai-Bin (1); Gao, Li-Qun (1) 2012, 33 (2):  182-186.  DOI: - Abstract ( 528 )   HTML   PDF (473KB) ( 655 )   Based on the classic differential evolution algorithm, an improved adaptive differential evolution algorithm is proposed. In this algorithm, the mutation rate is taken as a component of the solution space, varying with the evolving of the algorithm, so that the parameters of the algorithm can adapt well to the requirements of each stage in the evolution, thereby improving the performance of the algorithm. The algorithm was applied to system reliability analysis and the simulation analysis of three typical systems was performed. The result shows that the algorithm proposed has better optimization ability in comparison with relevant other algorithms. References | Related Articles | Metrics

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Output feedback sliding mode control for discrete-time MIMO systems Yu, Chi (1); Wang, Hong-Wei (2); Gong, Ming-Long (2) 2012, 33 (2):  187-190.  DOI: - Abstract ( 569 )   HTML   PDF (316KB) ( 816 )   For a class of multi-input multi-output (MIMO) uncertain discrete-time systems, of which the states are not fully measured, an improved output feedback sliding mode controller was designed. First, a sliding mode surface function was established by using Lyapunov function method and linear matrix inequality(LMI) technique, with the stability of the sliding mode system proved. Then, a reaching law based on power function was presented to weaken the chattering of the system. Simulation results show the feasibility and effectiveness of the algorithm proposed. References | Related Articles | Metrics

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A new method of measuring blood pressure indirectly Zhao, Hai (1); Peng, Hai-Xia (1); Zhu, Jian (1); Li, Xue-Bo (1) 2012, 33 (2):  191-194.  DOI: - Abstract ( 710 )   HTML   PDF (410KB) ( 1249 )   Existing detectors for pulse flow parameters can be used only after blood pressure measurement and their operation is inconvenient. Thus a new method was proposed for measuring the human body arterial blood pressure values. Based on the relationship between arterial blood pressure and the characteristic parameters of the photoelectric volume pulse waves, correlation analysis between the parameters and arterial systolic and diastolic blood pressures was performed to determine which parameters strongly correlate to the arterial systolic and diastolic blood pressures, with the dependence of arterial blood pressure on these parameters obtained by linear regression, and human blood pressure was thus indirectly obtained. Compared with the conventional methods, the proposed one is more convenient, can be applied to non-invasive optical detectors and has more potential applications. References | Related Articles | Metrics

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High-temperature oxidation thickening and sticking behavior during hot rolling in ferritic stainless steel Zhang, Chi (1); Wang, Xiao-Nan (1); Liu, Zhen-Yu (1); Wang, Guo-Dong (1) 2012, 33 (2):  195-198.  DOI: - Abstract ( 723 )   HTML   PDF (1857KB) ( 1431 )   High-temperature oxidation thickening of an ultra purified 21%Cr ferritic stainless steel (FSS) was studied by high-temperature oxidation test. A new method for simulating the sticking phenomenon of FSS during hot rolling was developed to investigate the effects of surface oxidation on the sticking behavior. The sticking mechanism was also discussed. The results indicated that the oxidation scale formed in heating furnace is thick and the secondary scale formed during hot rolling is very thin. The cracks on the hammers which formed during cycling rolling and cooling are the nucleation sites for sticking. The oxidation scale has a protective effect on the surface quality of the slab during hot deformation, decreasing the sticking phenomenon. References | Related Articles | Metrics

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Effects of ultra-fast cooling on yield ratio of X80 pipeline steel Zhou, Xiao-Guang (1); Lu, Min (2); Liu, Zhen-Yu (1); Wang, Guo-Dong (1) 2012, 33 (2):  199-202.  DOI: - Abstract ( 613 )   HTML   PDF (1761KB) ( 637 )   How ultra fast cooling affected the yield ratio of X80 pipeline steel was investigated by Metalloscope, SEM and TEM. The optimal technique for the pipeline steel with low yield ratio, high strength and high toughness was proposed. The experimental results revealed that both the strength and yield ratio of X80 pipeline steel increase gradually with decreasing the ending temperature of ultra fast cooling. When the ending temperature is about 655?°C, the microstructure of the steel consists of acicular ferrite, bainite and M/A islands, which make the steel have a good balance between strength and toughness. Under the cooling mode of "ultra fast cooling+air cooling+laminar cooling", the yield ratio decreases with increasing air cooling time. Ultra fast cooling can not only enhance the strength, but decrease the yield ratio of X80 pipeline steel, which is important for developing high strength and high-deformability pipeline steel. References | Related Articles | Metrics

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Microstructure and texture of high Nb interstitial-free steel Hou, Zi-Yong (1); Xu, Yun-Bo (1); Wang, Jia-Fu (1); Wu, Di (1) 2012, 33 (2):  203-207+227.  DOI: - Abstract ( 727 )   HTML   PDF (2418KB) ( 852 )   The microstructures and texture evolution of a novel high Nb bearing IF steel and conventional Nb+Ti bearing IF steel with the same cold rolling and annealing processes were investigated comparatively. The results revealed that the recrystallization temperature of the high Nb bearing IF steel is higher than that of the conventional Nb+Ti bearing IF steel, which is attributed to the addition of relatively high carbon content and excessive Nb which is a carbide forming element. Grain size of the high Nb bearing IF steel annealed at 875°C is finer (12.1 μm) than that of the conventional Nb+Ti bearing IF steel (15.4 μm); furthermore, the tiny Nb(C, N) precipitates (10~30 nm), which can refine grains, are found. The intensity of ND//{111} orientations (γ-fiber texture) favorable to r-value in the high Nb bearing IF steel is stronger and grows faster, in comparison with the conventional Nb+Ti bearing IF steel. EBSD analyses showed that there is more homogenous microstructure, more small-angle grain boundaries (&le15°) and low ΣCSL boundaries in the high Nb bearing IF steel. References | Related Articles | Metrics

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Modeling and identification of hydraulic bending roll control system Chen, Shu-Zong (1); Zhang, Dian-Hua (1); Sun, Jie (1); Li, Xu (1) 2012, 33 (2):  208-212.  DOI: - Abstract ( 545 )   HTML   PDF (1545KB) ( 781 )   Based on the analysis of a hydraulic bending roll control system, a transfer function of every link in the system was constructed, and then a theoretical model of the whole control system was established. In view of the difficulty in determining theoretical model parameters, a system identification method for a four-high mill was presented, with an accurate model of bending roll control system achieved using ARX(auto regressive exogenous) model. In the hydraulic bending roll closed-loop control system, an oil pressure setting and actual oil pressure were respectively used as the system's input and output, and the model parameters were estimated by least squares estimation method. The results showed that the output response of the identification model can reflect the dynamic characteristics of actual system well, which proves the feasibility of the ARX identification method for bending roll control system. References | Related Articles | Metrics

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Hot deformation behavior of alloy 800H Cao, Yu (1); Di, Hong-Shuang (1); Ma, Tian-Jun (2); Zhang, Jing-Qi (1) 2012, 33 (2):  213-217.  DOI: - Abstract ( 639 )   HTML   PDF (1231KB) ( 722 )   The hot deformation behavior and microstructure evolution of alloy 800H were investigated by high temperature single-pass compression tests at the temperatures ranging from 850 to 1050°C and the strain rates ranging from 0.01 to 10 s-1. Based on the data of single-pass compression tests, the flow stress curves of alloy 800H under different deformation conditions were plotted, and the mathematical model of flow stress was established through nonlinear regression. The hot deformation constitutive equations at different temperature intervals were established through linear regression. The effects of hot deformation conditions on the microstructure were analyzed. The results showed that the dynamic recrystallization is more likely to occur at a low strain rate and high deformation temperature. When deformation temperature is below 950°C, the dynamic recrystallization is inhibited by Cr23C6 carbide precipitated at grain boundaries. References | Related Articles | Metrics

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Development and application of ultra-fast cooling control system for H-beam Guo, Fei (1); Zhao, Xian-Ming (1); Peng, Liang-Gui (1); Wu, Di (1) 2012, 33 (2):  218-221.  DOI: - Abstract ( 496 )   HTML   PDF (847KB) ( 965 )   Ultra-fast cooling (UFC) equipment for H-beam steel is outlined. The UFC system can be adapted for the cooling requirements of H-beams with different specifications through the signal transfer in basic automation and the co-operation of hydraulic cylinders. Based on the development of H-beams and the requirements of UFC process, the temperature-drop models of water/air cooling were established, and the temperature control was achieved by modular design. The UFC process became reasonable gradually through the self-learning of the models. Operation results showed that the temperature difference between web and flange can be reduced to 30°C, and the readings of magnetic feet on the two hydraulic cylinders are broadly in line, thus the UFC system is controllable, precise and reliable. References | Related Articles | Metrics

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Effect of high magnetic field on solidification structure of half-infinite liquid Al/solid Cu diffusion couple Xu, Bo (1); Tong, Wei-Ping (1); Zuo, Liang (1); He, Ji-Cheng (1) 2012, 33 (2):  222-227.  DOI: - Abstract ( 505 )   HTML   PDF (2105KB) ( 734 )   The solidification of Al-Cu alloy was investigated by the liquid Al/solid Cu diffusion couples under the high magnetic field. The results showed that the α-Al cellular/dendrite crystal, Al-Al2Cu eutectic lamellar and Al2Cu hypereutectic are formed separately along the solidification direction. When a high magnetic field (up to 12 T) is applied to the liquid Al/solid Cu couples, the cellular crystals disappear, the primary dendrite arms coarsen and deflect from the solidification direction, the eutectic is distorted and its spacing depends nonlinearly on the magnetic field intensity, the interface of hypereutectic becomes regular, and the diffusion distance of Cu atoms decreases. XRD results showed that the peak strength of the α-Al (100) crystal plane becomes weak, but that of the (111) crystal plane is stronger. Those phenomena may be attributed to the magnetic field suppressing melt flow and the magnetic anisotropy. References | Related Articles | Metrics

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Isothermal section of Fe-rich corner in Fe-Pt-Au ternary system at 950C Xu, Xiao-Ning (1); Ren, Yu-Ping (1); Li, Jun-Jie (1); Qin, Gao-Wu (1) 2012, 33 (2):  228-231.  DOI: - Abstract ( 517 )   HTML   PDF (1203KB) ( 904 )   In order to control the homogeneous distribution of fine L10-FePt nano-phase in a non-magnetic matrix, it is necessary to systematically study phase diagrams of Fe-Pt-X systems. In this work, phase relationships and equilibrium phase compositions in the Fe-rich corner of the Fe-Pt-Au ternary system at 950°C were studied by both alloying method and diffusion couple technique using X-ray diffraction and scanning electron microscopy assisted with energy dispersive spectroscopy (SEM-EDS), thus the isothermal section of Fe-rich corner was constructed in this system at 950°C. The results showed that there exists a wide (γ Fe+αAu) and a narrow (γFe+L10-FePt) two-phase regions. The solubility of Au in the γFe phase increases from ~4% to ~15% with the addition of Pt, whereas the solubility of Fe in the αAu phase decreases rapidly. With the addition of Au, the solubility of Pt in the γFe phase decreases and the (γFe+L10-FePt) two-phase region remains unexpanded. References | Related Articles | Metrics

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Effect of NaY on microstructure and conductivity of (PEO)16LiClO4-EC composite electrolyte Qi, De-Jiang (1); Ru, Hong-Qiang (1); Bi, Xiao-Guo (2) 2012, 33 (2):  232-235.  DOI: - Abstract ( 510 )   HTML   PDF (1545KB) ( 791 )   Using nanosized NaY molecular sieves as filler, a novel solid-state composite polymer electrolyte (CPE) film (PEO)16LiClO4-EC-x wt% NaY (x=0, 3, 5, 8, 12, 20, 35) was prepared. Scanning electron microscopy, EDS analysis and AC impedance techniques were used to investigate the effect of NaY on the microstructure and conductivity of CPE films. The results showed that the addition of an appropriate amount of NaY inhibits the growth of PEO spherulites, and forms ultrabranch shape and crosslinked network which are beneficial to lithium-ion transport, thereby expanding the amorphous region where the lithium-ions transport. Meanwhile, an appropriate amount of organic solvent EC makes NaY powders distribute well in the electrolyte matrix. The ionic conductivity of (PEO)16LiClO4-EC-12 wt% NaY reaches 1.890×10-4 S·cm-1 at room temperature. References | Related Articles | Metrics

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Heat treatment technology for Cu/Al composite plates Liu, Jing (1); Yin, Jie (2); Xie, Pei-Pei (1); Wang, Ping (2) 2012, 33 (2):  236-238+257.  DOI: - Abstract ( 572 )   HTML   PDF (1529KB) ( 625 )   By using a metallograph and a universal material testing machine to observe the interface microstructure of Cu/Al composite thin plates and test their mechanical properties, the effect of heat treatment parameters on them was investegated. It is concluded that the strength of the composite plates decreases and their plasticity increases with increasing the annealed temperature or holding time. The interface width of the composite plates is 2~5 μm after annealing, with brittle compounds (CuAl2, CuAl and Cu9Al4) observed. The composite plates annealed at 410°C for 10 min exhibit the optimal balance of mechanical properties, i.e., heating up to 410°C then holding 10 min is an optimal annealing schedule. References | Related Articles | Metrics

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Theoretical analysis model for social stock of metallic substance Yue, Qiang (1); Wang, He-Ming (1); Lu, Zhong-Wu (1) 2012, 33 (2):  239-242.  DOI: - Abstract ( 613 )   HTML   PDF (608KB) ( 582 )   Combining substance flow analysis and groups of products life cycle chains, a theoretical analysis model for social stocks of metallic substance was developed. It is concluded from the model that the social stocks of metallic substance and their net increments are closely related to the factors such as metal product consumption, annual variation rate of metal product consumption and service lives of metal products, i.e., they will increase with the increase of the three factors. If the service lives of metal products are prolonged beyond average service lives, recycling rate of the social stocks will decrease. Analysis results can provide some reference for the decision making on industrial policies of metal industry. References | Related Articles | Metrics

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Calculation of best switching time of heat accumulating combustion Liu, Hui (1); Li, Ya-Bing (2); Chen, Wen-Zhong (1) 2012, 33 (2):  243-246.  DOI: - Abstract ( 749 )   HTML   PDF (475KB) ( 747 )   To research the influence of switching time on the temperature fluctuations in a combustion chamber, the discharge temperature of gas and excess heat recuperation efficiency in a regenerator, the best switching time was determined with high excess heat recuperation efficiency. A mathematical expression was established according to the relationship of the switching time to excess heat recuperation efficiency. A proper switching time was obtained from the expression with the highest excess heat recuperation efficiency obtained. For validation, the reasonable switching time was calculated on the certain conditions and compared with the diathermy time. Considering the effects of preheat temperature and gap volume of the regenerator on the switching time, the best switching time can be determined. References | Related Articles | Metrics

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Direct reduction of ore-coal composite pellets bearing low carbon content Zhu, Bing-Xiu (1); Wei, Guo (1); Jiang, Xin (1); Shen, Feng-Man (1) 2012, 33 (2):  247-250.  DOI: - Abstract ( 555 )   HTML   PDF (1176KB) ( 747 )   Using the direct reduction technology and the principle of melting and separation of slag and iron, the reduction of ore-coal composite pellets bearing low carbon content at a low temperature was investigated experimentally. The results showed that the reduction rate of these pellets was very fast. When the reduction reaction lasted for 10 min and for 20 min, the apparent reductivity reached about 84% and 88% (the maximum value), respectively. When the reaction time was prolonged further, a small quantity of direct reduced iron (DRI) on the surface of the pellets was re-oxidized. The FeO remained in the pellets after the reduction reaction reacted with SiO2, forming 2FeO·SiO2 with the low melting-point, which is beneficial to melting and separation of slag and iron. References | Related Articles | Metrics

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Cu-Zn-Al-Fe/HZSM-5 catalyst for direct synthesis of dimethyl ether Wang, Ming-Hua (1); Wang, Feng-Luan (1); Li, Chao (1); Zhai, Yu-Chun (1) 2012, 33 (2):  251-253.  DOI: - Abstract ( 586 )   HTML   PDF (573KB) ( 600 )   Cu-Zn-Al-Fe catalyst was prepared by the hydrothermal method, using HZSM-5 as a support. The influence of nitrate content, aging temperature and Fe content on the catalyst was investigated. SEM, BET, FT-IR and XRD were applied to the characterization of the catalyst. Dimethyl ether (DME) was synthesized by feeding CO2 and H2 into a reactor under the pressure of 4 MPa, the temperature of 260°C and the H2/CO2 ratio (volume fraction) of 3. The results showed that when the mass fraction of nitrate is 10% and the aging temperature is 150°C, the particle size of the catalyst is the minimum (about 500 nm) and the specific surface area is 200.6 m2/g. During synthesizing DME, the catalyst with 5%Fe shows the best effect, with CO2 conversion ratio of 41.4% and DME selectivity of 45.2% obtained. References | Related Articles | Metrics

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FLUENT simulation on vibration of oil return pipes for 5 m finishing mill edging rolls Tong, Kun (1); Liang, Dong-Wei (1); Song, Jin-Chun (1); Ni, Ke (1) 2012, 33 (2):  254-257.  DOI: - Abstract ( 633 )   HTML   PDF (1530KB) ( 767 )   The vibration of oil return pipes for edging rolls of a finishing mill which produces 5 m wide steel plates was systematically analyzed, and a mathematical model of the pipeline was established . 3D models for the oil return pipe were built and meshed by using the Gambit software. Simulation results were obtained with the FLUENT software. It is revealed that the vibrations and noises are caused by the cavitations and turbulence in the oil return pipe. A method for improving the oil return pipe was proposed and verified by simulation. The results showed that the cavitations and turbulence in the modified oil return pipe are reduced obviously and the vibration is alleviated effectively. The work in the paper provides a theoretical foundation for debugging and running the production line. References | Related Articles | Metrics

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Identification of random road spectrum based on inverse pseudo-excitation method Zhang, Li-Ping (1); Guo, Li-Xin (1) 2012, 33 (2):  258-261.  DOI: - Abstract ( 562 )   HTML   PDF (606KB) ( 912 )   The inverse pseudo excitation method was adopted to identify the random road spectra, and a road spectrum identification alogorithm for stationary random vibration of vehicles was deduced by a deterministic method. The power spectrum of road excitation was inversely deduced with the self-power spectrum and cross-power spectrum given, and then the power spectrum of vehicle vibration response to road excitation was calculated. The simulation compared the difference of the calculated and the actual road spectra and validated applicability of the deduction results. The results show that the inverse pseudo excitation method has good accuracy and high efficiency for solving the road spectrum, and it provides a new way to research vehicle vibration comfort and has a wide application prospects. References | Related Articles | Metrics

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Automatic dimensioning of parts based on geometric entity analysis Zhang, Wen-Lei (1); Yang, Peng (1); Yan, Zhi-Yuan (1); Wang, Cheng-En (1) 2012, 33 (2):  262-266.  DOI: - Abstract ( 619 )   HTML   PDF (1634KB) ( 1595 )   A model of part dimensioning information, which was used to describe part data for automatic dimensioning, was developed by an object-oriented method. An automatic dimensioning algorithm and its knowledge representation method were presented. Some key problems of the algorithm were discussed in detail, including the geometric entity analysis based on part topologies and features, the automatic dimensioning of drawing elements, the recognition and optimization of feature-related dimensions and redundant dimensions, and the dimension layout based on feature bounding boxes. An automatic dimensioning system was developed and applied to the engineering drawing of an aero-engine turbine disk. The result shows that the dimensions generated by this system are accurate, standard and well arranged. References | Related Articles | Metrics

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Surface defect recognition for steel strips by combining multiple classifiers Zhang, Yao (1); Liu, Wei-Wei (1); Xing, Zhi-Tao (1); Yan, Yun-Hui (1) 2012, 33 (2):  267-270.  DOI: - Abstract ( 622 )   HTML   PDF (915KB) ( 771 )   To solve the problems that a single classifier recognizes the surface defects of steel strips ineffectively and over-depends on training samples, a new method with combination of multiple classifiers was proposed. The LVQ and RBF neural networks, and the support vector machine were used as the basic classifiers. The weighted voting algorithm was applied to integrating these basic classifiers, thus the complementary of the recognition system was realized. The experiments showed that the common surface defects of steel strips such as zigzag edges, welding seams, inclusions and wrinkles can be more effectively recognized by the combined multiple classifiers. The classification accuracy is better than that of a single classifier, with the overall recognition rate above 96%. References | Related Articles | Metrics

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Building outline extraction from airborne LiDAR data based on RANSAC model Wang, Zhi (1); Li, Hui-Ying (2); Wu, Li-Xin (1); He, Zheng-Xiong (1) 2012, 33 (2):  271-275.  DOI: - Abstract ( 688 )   HTML   PDF (1947KB) ( 1644 )   The orthogonal polynomial filtering algorithm was applied to filtering the point cloud data of airborne LiDAR. The non-ground points were excluded continually by iteration and then the orthogonal polynomials were obtained by fitting the points which were close to the ground. The point cloud data were classified into ground and non-ground parts according to the height thresholds. A RANSAC-based building feature extraction algorithm was proposed, which can recognize and extract the information of roof planes and their building outlines fast and accurately from the non-ground point cloud data with noise. The airborne LiDAR data of Changchun city were used to experimentally verify the effectiveness and accuracy of the proposed algorithms. References | Related Articles | Metrics

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Back analysis of mechanical parameters of surrounding rocks based on GA-BP algorithm Guan, Yong-Ping (1); Song, Jian (1); Wang, Shu-Hong (1); Liu, Yu (1) 2012, 33 (2):  276-278+283.  DOI: - Abstract ( 735 )   HTML   PDF (446KB) ( 709 )   A displacement back analysis algorithm was developed for deriving the mechanical parameters of surrounding rocks. Given the drawbacks of BP neural network (BPNN) such as easily getting stuck in local minima and over long training time, a genetic algorithm with global optimization ability was used to optimize the weights and thresholds of the BPNN. The parameters of surrounding rocks were designed in the initial domain by the uniform method, which reduced the iterative time and improved the forecast accuracy. Applying the method to the back analysis of the mechanical parameters of Lu¨chunba railway tunnel, we introduced the parameters as obtained into the numerical model for computing. The results show that the errors of the calculated and measured values were -8.9% and 4.5%, respectively, which illustrates the reliability and applicability of the method. References | Related Articles | Metrics

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Effect of particle size on galena flotation kinetics using fuzzy logic Li, Jun-Wang (1); Sun, Chuan-Yao (2); Yin, Wan-Zhong (1); Yuan, Chuang (1) 2012, 33 (2):  279-283.  DOI: - Abstract ( 481 )   HTML   PDF (1389KB) ( 694 )   In order to study the effect of particle size on galena flotation kinetics, the batch flotation tests were conducted. The results showed that the flotation recovery rate increases initially and then decreases with increasing particle size, while the flotation rate constant decreases gradually. Variance analysis showed that only the flotation rate constant is significantly influenced by particle size. A multi-input/single-output (MISO) fuzzy logic inference system was established with MATLAB, where particle size and flotation time were input variables and cumulative recovery rate was output variable. Simulation analysis showed that the correlation coefficients were 0.984, 0.981, 0.981, 0.993 and 0.988 for average particle sizes of 34, 46, 64, 87 and 112.5 μm, respectively. The studies prove that it is feasible and effective to study mineral flotation kinetics using fuzzy logic theory. References | Related Articles | Metrics

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Performance-based seismic level division and index choosing for RC column strengthened with FRP Sheng, Guo-Hua (1); Zhu, Fu-Sheng (1); Xu, Ming-Lei (1) 2012, 33 (2):  284-287+304.  DOI: - Abstract ( 547 )   HTML   PDF (1168KB) ( 728 )   The performance-based seismic design (PBSD) theory was introduced into the performance analysis of RC frame column strengthened with FRP. The anti-seismic performance was divided into 5 levels in terms of applicability, repairability and security, i.e., fully operational level, temporarily operational level, repairable level, life safety level and collapse prevention level. The drift limits of the columns were statistically analyzed, and the relationship was discussed between the drift and longitudinal reinforcement ratio ρs, confining reinforcement characteristic values λv, shear span-to-depth ratio λ, axial compression ratio n, as well as FRP characteristic values λf, with the conclusion obtained that n and λf significantly affect the drift. Using the drift as performance index and introducing n and λf into the quantization of the drift, the drift limit of PBSD was presented. References | Related Articles | Metrics

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Numerical simulation on corrosion-expansion cracks of reinforced concrete based on plastic damage theory Qiu, Zhao-Guo (1); Zhan, Yu (1); Zhang, Feng-Peng (2) 2012, 33 (2):  288-291.  DOI: - Abstract ( 603 )   HTML   PDF (1047KB) ( 1406 )   FEM models for corrosion-expansion cracks in reinforced concrete protective layer were built based on plastic damage theory. Corrosion-expansion correlation was simulated by loading displacement. Taking the maximum strain as the criterion, the concrete damage was achieved by reducing Young's modulus. The generating and propagating trajectories of internal and surface corrosion-expansion cracks were researched. For visually representing crack trajectories, a field variable under tensile condition was defined through a subroutine USDFLD in ABAQUS. The corresponding critical corrosion rates of the internal and surface cracks were calculated. The influences of the concrete cover thickness, reinforcement diameter and corrosion-expansion coefficient on the critical corrosion rates were studied. The results showed that the lateral cracks propagate from the surface of steel bar inside the concrete, while vertical cracks propagate from the surface of the concrete cover. The critical corrosion rates decrease with the increase of the bar diameter and corrosion-expansion coefficient. The effect of the corrosion expansion coefficient is more prominent, while the influence of protective layer thickness on the critical corrosion rate is not obvious. References | Related Articles | Metrics

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An approach to identify relational capital factors using linguistic assessment information Zhou, Li-Ming (1); Fan, Zhi-Ping (1) 2012, 33 (2):  292-295.  DOI: - Abstract ( 429 )   HTML   PDF (244KB) ( 579 )   According to the essential ideas of DEMATEL method, linguistic assessment information provided by experts was used to represent the correlation between relational capital factors, and it was well processed and aggregated on the basis of relational capital factors integration. First, linguistic assessment information was quantized and factors' direct evaluation matrix was established and standardized, based on which the factors' indirect evaluation matrix was obtained. The comprehensive evaluation matrix is the summation of the as-obtained matrixes. Second, the prominence and relation of the relational capital element were calculated to determine sorting and classification of the elements. Finally, an application case was given to illustrate the proposed approach. References | Related Articles | Metrics

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A dynamic comprehensive evaluation method reflecting resource background difference Guo, Shan-Rui (1); Li, Wei-Wei (1); Guo, Ya-Jun (1) 2012, 33 (2):  296-299.  DOI: - Abstract ( 406 )   HTML   PDF (158KB) ( 571 )   Given the resource background difference of objects to be evaluated, a dynamic comprehensive evaluation method was presented. The dynamic development situations of every object's evaluation value and its corresponding resource background were provided according to difference driven principle and timing discount factor. Based on this, the rules adjusting evaluation values were given according to the resource background development. An evaluation model based on difference driven principle was proposed, which can maximize the difference among the objects. Finally, an example was given to introduce the application of the method. The result shows that the method can improve the fairness and comparability of the evaluations. References | Related Articles | Metrics

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Composite proton conductors based on ionic liquid 1-buty-3-methylimidazolium dihydrogen phosphate and heteropolyacids Che, Quan-Tong (1); Feng, Li (1); He, Rong-Huan (1) 2012, 33 (2):  300-304.  DOI: - Abstract ( 737 )   HTML   PDF (1096KB) ( 673 )   Anhydrous composite proton conductors were prepared with ionic liquid 1-buty-3-methylimidazolium dihydrogen phosphate (BMIMH2PO4) and heteropolyacids (HPA), i.e., phosphotungstic acid (PWA) and silicotungstic acid (SiWA). The conductivities of the composite proton conductors were investigated at 80~180°C without humidification. The proton conducting mechanism of PWA/BMIMH2PO4 composite was studied. The results indicated that the dopant of phosphorous pentoxide (P2O5) in the composite enhances the proton conductivity and the presence of the ionic liquid BMIMH2PO4 promotes the proton conduction in the anhydrous composite proton conductors. The conductivity of PWA/BMIMH2PO4 (mole ratio=1:3) was 2.6×10-3 S/cm at 160°C under anhydrous condition. In the presence of P2O5 (10wt%), the corresponding conductivity was increased to 4.1×10-2 S/cm under the same conditions. References | Related Articles | Metrics