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15 June 2010, Volume 31 Issue 6 Previous Issue    Next Issue
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A new approach to static output feedback control for singular systems Shi, Shu-Hui (1); Zhang, Qing-Ling (1); Yang, Chun-Yu (2); Yuan, Zhong-Hu (3) 2010, 31 (6):  761-764.  DOI: - Abstract ( 319 )   HTML   PDF (244KB) ( 785 )   A new and simple method is proposed to design the static output feedback controller for singular systems. The bilinear inequality including Lyapunov matrix and output feedback gain matrix is decoupled by introducing an auxiliary matrix variable and, combining with the variable substitution method, the bilinear inequality and the non-strict inequality including Lyapunov matrix are transformed into a linear matrix inequality (LMI). In this way, the sufficient conditions are available to the admissibility of closed-loop singular system. An output feedback controller is given. A numerical example is given to show the effectiveness of the method proposed, which is easy to extend to the static output feedback control of normal systems. References | Related Articles | Metrics

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A model based on audience rating data to predict the numbers of audience responding to an advertisement Sun, Ying (1); Mao, Zhi-Zhong (1) 2010, 31 (6):  765-768.  DOI: - Abstract ( 332 )   HTML   PDF (223KB) ( 683 )   Based on the data of audience rating, a model was developed to predict the number of audience who will respond to an advertisement, thus solving the problem that there are no effective indices to evaluate the efficiency of advertising activities. The model is composed of an exposure frequency distribution submodel and a prediction submodel based on the former one, and both are described for the estimate of their parameters. The genetic algorithm method is introduced to estimate the parameters of the prediction submodel. With the real data of a financial organization taken as example to verify the model developed, comparative results between predicted and actual number of the audience responding to an advertisement showed that the proposed model can offer a relative accurate prediction without the support of deciders' experience if the data of audience rating are easy to acquire. Therefore, the proposed model can be used to provide quantitative evaluation indices in practice at advertising activities. References | Related Articles | Metrics

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Application of HDEHS algorithm to structural engineering Zou, De-Xuan (1); Gao, Li-Qun (1); Wu, Jian-Hua (1); Wu, Pei-Feng (1) 2010, 31 (6):  769-772.  DOI: - Abstract ( 259 )   HTML   PDF (1014KB) ( 619 )   To enable the HS (harmony search) algorithm to transcend its limited capability of local optimum, the mutating and crossing operations of DE (differential evolution) algorithm are introduced into the HS algorithm so as to improve the latter, i.e. the hybrid differential evolution-harmony search (HDEHS) algorithm. It is able to prevent the limitation of its local optimum effectively, besides its strong convergence. Experimental results revealed that the HDEHS algorithm as an efficient alternative can find out better solutions to the optimization problem of structural engineering in comparison to the methods as shown in earlier works. References | Related Articles | Metrics

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Bifurcation of a class of time-delayed EEG models and its control Li, Chun-Sheng (1); Wang, Hong (2); Zhang, Xue (3) 2010, 31 (6):  773-776.  DOI: - Abstract ( 236 )   HTML   PDF (282KB) ( 583 )   Robinson et al studied a class of reduced EEG model, which was discussed with aim to understand its bifurcation character. Considering the time delay of information transmission between the excitatory and inhibitory neuronal population, the effect of time delay on the stability of the reduced model was studied, as well as the conditions under which the Hopf bifurcation occurs. The results showed that the reduced model can keep up its stability when time delay is restricted within a certain threshold. Furthermore, a derivative feedback controller was designed to eliminate the Hopf bifurcation. Numerical simulation verified theoretically the effectiveness of the conclusions as above. References | Related Articles | Metrics

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EEG signal amplifier design based on driven-right-leg technology Sun, Yu-Ge (1); Ye, Ning (1); Yu, Yan-Bo (1) 2010, 31 (6):  777-781.  DOI: - Abstract ( 838 )   HTML   PDF (546KB) ( 3448 )   A high-performance EEG signal amplifier was designed, where the differential amplifier circuit, driven-right-leg circuit and preamplifying parts in the designed amplifier can denoise the common-mode interference signals. With the EEG signal amplified by the preamplifier and 2-stage post-amplifier, two low-pass filters and two 50Hz traps were arranged reasonably in design to denoise the high/medium-frequency interference in EEG signal effectively, thus enabling the efficient EEG signal detection without shielded enclosure. Testing results showed that the performance of all parts of the amplifier comes up to the indices as required in design. The effectiveness of the design was proved by the real EEG signal sampled from the scalp of the detected person. References | Related Articles | Metrics

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Public blog clustering algorithm based on revision by comments Guo, Peng-Wei (1); Gao, Ke-Ning (1); Zhang, Bin (1) 2010, 31 (6):  782-785.  DOI: - Abstract ( 248 )   HTML   PDF (197KB) ( 556 )   Public blog clustering is an effective way to process blog information. A public blog clustering algorithm was therefore proposed, based on the revision by comments. Analyzing the information hierarchy of public blog, a public blog attribute model based on the general attributes of blog pages was developed as a basis on which the public blog was clustered. Then, after the initial clustering, the comments on the clustered public blog were taken in to revise the clustered blog. The clustered results were evaluated with entropy and purity, and two testing schemes were designed according to different ways of taking the comments in. One was making the comments on public blog participate in clustering process directly, the other was making use of the comments after clustering to play the role of revision. Testing results showed that, in most cases, the latter was more effective than the former. References | Related Articles | Metrics

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Service matchmaking algorithm based on behavioral effect Liu, Ying (1); Zhang, Bin (2); Liu, Guo-Qi (1); Wang, De-Shuai (2) 2010, 31 (6):  786-790.  DOI: - Abstract ( 362 )   HTML   PDF (254KB) ( 966 )   How to improve the efficiency of service matchmaking algorithm to provide service discovery is a key problem along with the development and application of service. But the existing way in matching still depend on the semantic matchmaking mechanism by which the service stays at an atom-like level. With the internal logic of service becomes more and more complex, the big-grain-size service emerges, which requires a behavioral description for the complex business logic because the existing matchmaking algorithms are incompatible with the matchmaking of such a service. Characterizing the behavior of service, a relevant matchmaking algorithm based on behavioral effect is proposed. The behavioral effect is defined including event, precondition and result, and then they are matched with each other to compute what the users demand and the matching accuracy between description and service required. Experimental results verify the feasibility and effectiveness of the algorithm proposed. References | Related Articles | Metrics

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Research of execution log-based Web service QoS acquisition mechanism Zhang, Ming-Wei (1); Zhang, Bin (2); Huang, Li-Ping (1); Zhu, Zhi-Liang (1) 2010, 31 (6):  791-794.  DOI: - Abstract ( 332 )   HTML   PDF (930KB) ( 504 )   To solve the problem of the acquisition of Web service QoS effectively, this paper proposes an execution log based Web service QoS acquisition approach from the statistic point of view. Firstly, based on the Web service QoS attributes desiring to be acquired, this approach analyzes the log contents that have to be logged in and generates the execution log. Then, the Web service QoS point data set is extracted. For the problem that the QoS point data collected by real execution is small and distributes ununiformly, corresponding solutions are given. Finally, on the basis of the generated QoS point data set, the querying and prediction approaches of Web service QoS data are described. Experimental results show that the Web service QoS acquisition approach is accurate and practicable. References | Related Articles | Metrics

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On the reference node selection algorithm based on MCLP in WSN Xu, Jiu-Qiang (1); Wang, Cheng-Long (1); Zhang, Yuan-Yuan (1); Liu, Wei (1) 2010, 31 (6):  795-798.  DOI: - Abstract ( 305 )   HTML   PDF (1069KB) ( 784 )   To get rid of the shortcoming of low coverage/reliability of both empirical algorithm and SHARP algorithm, the reference location nodes selected with the Maximum Coverage of the Layout Problem (MCLP) were investigated introducing the Greedy Random Adaptive Search Procedure (GRASP) into MCLP. Then, the Coverage based Reference node Selection (CRS) algorithm was proposed where a maximum triangular coverage should be laid out then spread over step by step so as to select the locations of reference nodes. The result of the simulation tested with Matlab showed that the CRS algorithm can make the coverage bigger at the cost of prolonging the time for layout without increasing extra overheads for hardware. References | Related Articles | Metrics

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On the layer and community in software network Li, Bo (1); Zhao, Hai (1); Wang, Jia-Liang (1); Yang, Zhan-Kun (1) 2010, 31 (6):  799-802.  DOI: - Abstract ( 299 )   HTML   PDF (938KB) ( 486 )   Layer and community were first introduced into software network and investigated. Some relevant concepts were therefore defined including the level, community, chief and degree of interweavement. Community reflects the modularity and fault tolerance of software, while the level and degree of interweavement reflect the coupling. Then, some softwares were selected individually as samples. It was found that if the number of nodes in a software network is greater than 1000, the number of nodes in the communities at all levels, among which the chief node of the maximum number of communities at level-0 is selected as the chief tends to correspond with a logarithmic function with the increasing route length, while no obvious correlation is found between the degree of interweavement and number of nodes. The results are instructive to the R&D of software and provide a measure set for new software. References | Related Articles | Metrics

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On the microstructure and mechanical properties of hot-rolled Nb-Ti microalloyed multiphase steel Zheng, Dong-Sheng (1); Zhu, Fu-Xian (1); Zhang, Ming-Ya (1); Li, Yan-Mei (1) 2010, 31 (6):  803-807.  DOI: - Abstract ( 293 )   HTML   PDF (926KB) ( 669 )   The 14mm-thick Nb-Ti microalloyed hot-rolled multiphase steel plate was developed by two-stage rolling and subsequent three-step cooling, then it was characterized by optical microscopy, SEM, TEM, XRD, EBSD (electron back-scattered diffraction) and other tests to investigate its microstructure and mechanical properties. The results indicated that the microstructure of the steel specimen is composed of ferrite, bainite and small amount of martensite, and that the mean yield strength, tensile strength and percentage elongation are 518MPa, 616MPa and 41%, respectively. The existence of lots of big-angle ferrite grain boundaries, near-equiaxial ferrite grains and small bainitic beams significantly improves the ductility. The refinement of ferrite grains and bainitic structures, fine (Nb, Ti)C particles and the dislocations in ferrite and lath bainite increase the strength. References | Related Articles | Metrics

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Study on austenite grain coarsening temperature of a steel with low sensitivity to weld crack Lan, Liang-Yun (1); Qiu, Chun-Lin (1); Zhao, De-Wen (1); Gao, Xiu-Hua (1) 2010, 31 (6):  808-811.  DOI: - Abstract ( 359 )   HTML   PDF (1315KB) ( 595 )   The change in austenite grain size of a steel with low sensitivity to weld crack was investigated via high-temperature quenching test. The correlation between reheating temperature, holding time, starting temperature for austenite grain coarsening and micro-hardness was discussed via metalloscope/TEM observation, hardness test and the equations of second phase particles' solubility product. The results showed that the austenite grain coarsening temperature of specimens is about 1200°C. When the reheating temperature is lower than 1200°C, a great number of fine second phase particles will hinder the austenite grains from coarsening, and they will be dissolved and growing abnormally when higher than 1200°C. It was found that the reasonable reheating temperature range is from 1150°C to 1200°C, within which micro-hardness of quenched structure is lower than HV330. References | Related Articles | Metrics

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Causal analysis of cold bending cracks of TT610L steel plates for chassis frames Yi, Hai-Long (1); Song, Yong-Jun (2); Xu, Zhao-Guo (2); Wang, Guo-Dong (1) 2010, 31 (6):  812-815.  DOI: - Abstract ( 350 )   HTML   PDF (1351KB) ( 571 )   Cracks were often found on TT610L steel plates for chassis frame during cold bending. A causal analysis was therefore made via chemical composition, testing for mechanical properties, optical microscopy, SEM and EDS. The results showed that the cold bending cracks along thickness of TT610L steel plate specimens are mainly caused by the Al2O3 and SiO2 inclusions in the steel, while the cracks on plate surface are mainly caused by the SiO2 inclusion. The abnormal aggregation of these inclusions is just the cause of cold bending cracks. The problem of cold bending cracks has been solved efficiently by optimizing the continuous casting process and stabilizing the continuous rolling speed. References | Related Articles | Metrics

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Influence of horizontal steady magnetic field on second-phase distribution in Zn-10%Bi hypermonotectic alloy Zhang, Lin (1); Wang, En-Gang (1); Kang, Zhi-Qiang (1); He, Ji-Cheng (1) 2010, 31 (6):  816-819.  DOI: - Abstract ( 253 )   HTML   PDF (805KB) ( 493 )   The second-phase segregation is highly liable to occur in the solidification process of Zn-Bi hypermonotectic alloy, because of the liquid-liquid separation reaction. The magnetic field can suppress the migration of second-phase droplets in the solidification process. An experiment was done for casting the Zn-Bi hypermonotectic alloy into water-cooled copper mould in a horizontal steady magnetic field, to investigate the effect of magnetic field on the solidified structure of the alloy, where the moving direction of second-phase droplets in each part of the sample have a different angle with the magnetic field. The results showed that the magnetic field can suppress the Marangoni motion of Bi-rich phase, and the magnetic field has most obvious effect when its direction is parallel to the Marangoni motion of Bi-rich droplets. References | Related Articles | Metrics

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Effect of mixing processes on SiCp distribution in SiCp/Al composites Liu, Yue (1); Wang, Bao-Yong (1); Zhang, Ya-Jing (1); Lu, Chun-Yu (1) 2010, 31 (6):  820-823.  DOI: - Abstract ( 291 )   HTML   PDF (1259KB) ( 651 )   The 12% SiCp/2024Al (in volume fraction) composite was prepared by mixing the element powder in a 3-D high-efficiency mixer. The effect of mixing process parameters on the spatial distribution of SiC particles were investigated. The experimental results indicated that the ball/charge weight ratio, mixing time and particle size of SiC affect greatly the distribution of SiC in the matrix of the composite. When the ratio is 1:2, it is difficult to achieve the uniform distribution of SiC particles because of low energy input. When the ratio is 5:1, the distribution uniformity of SiC particles is improved gradually with mixing time but cannot be improved much longer at a certain moment. When the ratio is 5:1 with the mixing time 20h, the 3.5μm SiC particles are the best of uniform distribution in matrix, whereas the 0.8μm SiC particles may form conglomerates in matrix. References | Related Articles | Metrics

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Relationship between smoke particle concentration and structural characteristics of trace of copper wire fused due to short-circuit Gao, Wei (1); Liu, Chang-Sheng (1) 2010, 31 (6):  824-826+833.  DOI: - Abstract ( 287 )   HTML   PDF (1123KB) ( 549 )   According to the environment where short-circuit of copper wire stay, the effect of smoke particle concentration on such structural characteristics as grain boundaries and pores as shown in the trace of fused copper wire was investigated. The results showed that with the increasing smoke particle concentration the grain boundaries in the trace turn to discontinuity from continuity and the number and area fraction of pores both increase gradually. It implies that there is a correspondence between the area fraction of pores and smoke particle concentration, i.e. if the concentration remains unchanged, the highly viscous smoke particles affect greater the formation of pores in the trace than lowly viscous smoke particles. References | Related Articles | Metrics

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Failure behavior of Au interconnects under a high density of alternating current Wang, Ming (1); Zhang, Bin (1); Liu, Chang-Sheng (1); Zhang, Guang-Ping (2) 2010, 31 (6):  827-829.  DOI: - Abstract ( 352 )   HTML   PDF (259KB) ( 566 )   The failure behavior of Au interconnects, 2 μm wide and 200 nm thick, at high-density alternating current was investigated. Analyzing the temperature field model of the failure melting process of Au interconnects under the action of alternating current, an analytic solution to the temperature field at high current density was given. The comparison between experimental data and theoretically calculated values revealed that under the high current density AC loading the Au interconnects will fuse and then fail, which is due to the local overheating rather than the thermal fatigue-induced damage. References | Related Articles | Metrics

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On the roll bending force preset for unsteady rolling on cold strip tandem mill Liu, Jia-Wei (1); Zhang, Dian-Hua (1); Wang, Jun-Sheng (2); Wang, Peng-Fei (1) 2010, 31 (6):  830-833.  DOI: - Abstract ( 314 )   HTML   PDF (1005KB) ( 518 )   In the cold rolling process in unsteady state, the set value of roll bending force is important to strip flatness control system. Based on both the theoretical analysis and practical applications, the mechanics and control method were applied to analyzing the roll bending force preset, as well as effects of rolling force, friction force and acceleration/deceleration on the roll bending force. A relevant mathematical model was therefore developed in reduced expression. The results indicated that the roll bending force can be readjusted by the influencing coefficient of rolling force on it, while the rolling speed will affect the roll bending force through friction force. This model has been applied successfully to the 1450 tandem mill for cold rolling and achieved good control effect, thus providing theoretically support for controlling the roll bending force in unsteady state. References | Related Articles | Metrics

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Study on stable operation range of premixed gas combustion in porous media burner Liu, Hui (1); Dong, Shuai (2); Li, Ben-Wen (2); Chen, Hai-Geng (1) 2010, 31 (6):  834-837.  DOI: - Abstract ( 281 )   HTML   PDF (515KB) ( 752 )   The combustion of methane/air mixture in a two-section porous burner was numerically simulated for the optimal design of a porous media burner. The software FLUENT with self-designing codes was used to solve a two-dimensional transient mathematical model of the combustion. The effects of the parameters, such as equivalence ratio, radiative extinction coefficient and thermal conductivity of the porous media on the range of stable burning rate were investigated. The results showed that the difference of maximum and minimum limits of burning rate enlarges from 0.12 to 0.72 when the equivalence ratio increases from 0.55 to 0.9 and the maximum and minimum limits of burning rate both increase obviously. Compared with the reference example, if the downstream thermal conductivity is 5 times greater than its original value and the upstream thermal conductivity remains unchanged, the difference of maximum and minimum limits of burning rate reaches 0.47. It was found that the radiative extinction coefficient of upstream section increases but that of downstream one remains unchanged, a relatively biggest stable operation can be provided. References | Related Articles | Metrics

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Effect of surface modification on photocatalytic effect of titanium-bearing blast furnace slag Lei, Xue-Fei (1); Xue, Xiang-Xin (2); Yang, He (2) 2010, 31 (6):  838-842.  DOI: - Abstract ( 296 )   HTML   PDF (613KB) ( 537 )   With the titanium-bearing BF slag as starting material, the feasibility to reduce Cr(VI) in aqueous solution with the surface modified titanium-bearing blast furnace slag (SMTBBFS) used as a photocatalyst was investigated. The photocatalyst was characterized by X-ray diffraction (XRD), UV-vis diffuse reflectance spectra, thermogravimetric analysis (TG), Fourier transform infrared spectroscopy (FTIR) and scanning electronic microscopy(SEM). The photocatalytic effects of different SMTBBFS catalysts were evaluated by the photocatalytic reduction of Cr(VI) under UV-vis light irradiation. For the photocatalytic reduction of Cr(VI), the photocatalytic effect of SMTBBFS catalyst is found to be strongly dependent on CaTiO3/TiO2 ratio, adsorption capacity and surface acidity, and the optimum H2SO4-doping proportion is 2.5%. References | Related Articles | Metrics

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Physical modeling of stirring and mixing in bath of top-bottom-side blown converter Zhong, Liang-Cai (1); Zhu, Ying-Xiong (1); Lai, Zhao-Yi (2); Chen, Bo-Yu (2) 2010, 31 (6):  843-847.  DOI: - Abstract ( 280 )   HTML   PDF (1269KB) ( 607 )   With a physical model developed for the top-bottom-side (TBS) blown converters, the effects of blowing process parameters on stirring and mixing behavior in the converter bath were investigated experimentally. The results showed that the flowrate of side-blowing gas affects greatly the bath mixing time, and a critical value of side-blowing gas flowrate is found in the TBS blown converters. Horizontal stirring effect in the bath is intensified gradually and the mixing time is shortened when the side-blowing gas flowrate is increased but lower than the critical value. But, when the side gas flowrate reaches the critical value, the mixing time in the bath drops considerably and, with the side-blowing gas flowrate further enhanced, it no longer changes obviously. A side nozzle with small section area as possible is recommended under the precondition that large enough side-blowing gas flowrate can be provided. In addition, an appropriate bottom-blowing gas flowrate is beneficial to the mixing in the TBS blown converter bath, and the change of top lance height or top-blowing gas flowrate affects unobviously the mixing time in the TBS blown converter bath. References | Related Articles | Metrics

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Formation of MgO·Al2O3 spinel inclusions in 409L stainless steel Li, Shuang-Jiang (1); Li, Yang (1); Jiang, Zhou-Hua (1); Liang, Lian-Ke (1) 2010, 31 (6):  848-851.  DOI: - Abstract ( 366 )   HTML   PDF (1316KB) ( 794 )   Based on VOD vacuum refining process, the composition and morphology of MgO·Al2O3 compound inclusion in 409L stainless steel deoxidized by aluminum were analyzed. A phase diagram between MgO, MgO·Al2O3 and Al2O3 at 1873K was drawn through thermodynamic calculation to investigate the thermodynamic conditions of MgO·Al2O3 inclusion formation and transformation. The results showed that the pure MgO·Al2O3 phase of spinel compound inclusion in molten steel present amorphous structure, where the inclusion size is about 5μm. On the condition that Al content is controlled at 0.04 wt% in molten steel together with w(Mg) ≥ 1.3 × 10-8, the MgO·Al2O3 inclusion will form Al2O3, it will transform into MgO inclusion if w(Mg) ≥9.7 × 10-7. References | Related Articles | Metrics

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Synthesis of zirconia-mullite composite materials with fly ash as raw material by reaction sintering process Ma, Bei-Yue (1); Li, Ying (1); Zhai, Yu-Chun (1) 2010, 31 (6):  852-855.  DOI: - Abstract ( 315 )   HTML   PDF (600KB) ( 634 )   Zirconia-mullite composite materials were synthesized by reaction sintering process, with fly ash, zircon and alumina micro powder as raw materials. The influence of sintering temperature on the linear shrinkage ratio, density, water absorbability, crushing resistance at normal temperature and thermal shock resistance of the synthesized materials were investigated. The phase composition and microstructure of the synthesized materials were characterized by XRD and SEM. The results indicated that the zirconia-mullite composite materials with high crushing resistance, thermal shock resistance and sinterability can be synthesized at 1600°C for 4h. It was found that the zirconia in the synthesized materials is mostly in particle shape with an average grain size about 5~10μm, and the particles are uniformly distributed in the mullite matrix. References | Related Articles | Metrics

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Effect of different TFS black sheets on surface morphology and corrosion resistance of TFS products Li, Jian-Zhong (1); Zhou, Geng-Rui (2); Huang, Jiu-Gui (2); Tian, Yan-Wen (1) 2010, 31 (6):  856-859.  DOI: - Abstract ( 340 )   HTML   PDF (879KB) ( 610 )   Effect of the metallographic structures of CA, BA and DR black sheets on the surface morphology of TFS products was investigated via metalloscope and SEM. In addition, the corrosion resistance of TFS products was evaluated by the iron solubility values and electrochemical polarization curves. The results showed that in the compact surface Cr-coating of BA black sheet with low porosity the grains are larger and coarser in comparison with that of CA sheet, while the evident microcracks are found in the surface Cr-coating of DR sheet. And the corrosion resistance of T2.5-BA Cr-coating sheet is higher than that of CA and DR sheets under the same schedules. As to the TFS products with CA black sheets, the more frequent the modulations, the lower the corrosion resistance. References | Related Articles | Metrics

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Synthesis of LiFePO4 by solid-state method with raw materials embedded in graphite and electrochemical properties Kang, Xiao-Xue (1); Tian, Yan-Wen (1); Qu, Tao (2) 2010, 31 (6):  860-863.  DOI: - Abstract ( 576 )   HTML   PDF (1338KB) ( 685 )   LiFePO4 was successfully synthesized as a product via one-step solid-state reaction during which the raw materials were embedded in graphite powder instead of the protective atmosphere when heated at high-temperature. The structure, morphology and electrochemical properties of the product were investigated by XRD, FTIR, SEM and galvanostatic charge/discharge test. The process of lithiation/delithiation of Li+ in LiFePO4 electrode was studied by cyclic voltammetry. The results showed that the pure-phase olivine-type LiFePO4 composed of near spherical particles in sub-micrometered size can be obtained by this improved solid-state method. The LiFePO4 thus prepared has favorable multiplication rate and cycling stability. The initial discharge specific capacity is 148.3 and 131.9mAh·g-1 if the rate is 0.1 C and 1 C, respectively; and after the charge/discharge action cycles 50 times the capacity holding rate is 96% and 90% if the rate is 1 C and 5 C, respectively. As calculated according to cyclic voltammetry, the apparent Li+ diffusion coefficients are 1.64×10-13 and 1.94×10-13 cm2·s-1 at the peaks of corresponding CV curves of anode and cathode, respectively. References | Related Articles | Metrics

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Study on pore evolution of Al foams prepared by powder metallurgy Wang, Lei (1); Yao, Guang-Chun (1); Luo, Hong-Jie (1); Zu, Guo-Qi (2) 2010, 31 (6):  864-867.  DOI: - Abstract ( 231 )   HTML   PDF (575KB) ( 669 )   Changes in pore morphology and wrinkles on the inner surface wrinkling of pores of Al foams prepared by powder metallurgy (PM) were investigated for different foaming time. The results showed that the bubble shape evolves from near spherical pores to polygonal ones with foaming time. With Plateau borders become smaller gradually, cell walls get thinner, even local fracture and, finally, the inevitable rupture and coalescence of pores. The crack-like pores found in the early foaming process is just the inherent characteristics of Al foams prepared by PM, which are caused by the release stressing in the direction perpendicular to compacting load inside the PM precursors. The pore evolution process is reflected by the wrinkles on its inner surface, i.e. the inner surface is rather smooth with a few wrinkles in the early foaming process, then the wrinkles are bulging out and, at last, the wrinkle belts form on the inner surface due to gravitational effect and increasing surface energy. References | Related Articles | Metrics

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Synthesis of NiFe2O4 spinel nanopowder via low-temperature solid-state reactions Zhang, Zhi-Gang (1); Yao, Guang-Chun (1); Ma, Jia (1); Hua, Zhong-Sheng (1) 2010, 31 (6):  868-872.  DOI: - Abstract ( 356 )   HTML   PDF (1417KB) ( 680 )   NiFe2O4 spinel nanopowder was synthesized by low-temperature solid-state reactions where NaCl was taken as dispersant and FeSO4·7H2O, NiSO4·6H2O and NaOH as starting materials. The precursors prepared by grinding the dispersant and reacting substances sufficiently at room temperature were calcined to obtain NiFe2O4 spinel nanopowder. The effects of NaCl content, calcining temperature and holding time on the particle size and powder morphology were investigated emphatically using X-ray diffraction(XRD) and scanning electron microscopy (SEM) to characterize the as-prepared product. The results showed that the NiFe2O4 spinel nanopowder prepared by calcining the precursor with 20wt% NaCl doped in the grinding process at 800°C for 1.5h is of pure cubic spinel structure with an average particle size about 75nm. References | Related Articles | Metrics

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GA-based optimum profile modification of spur gears for vibration damping Yuan, Zhe (1); Sun, Zhi-Li (1); Wang, Dan (1); Chen, Cong-Hui (2) 2010, 31 (6):  873-876.  DOI: - Abstract ( 343 )   HTML   PDF (1106KB) ( 575 )   To determine the parameters of gear profile modification accurately, the effect of transmission error on gear vibration was analyzed to simulate the meshing process of a pair of gears via FEM. With the GA(genetic algorithm) introduced into the process to reduce the fluctuation of transmission error, the profile modification parameters of spur gears were designed optimally and accurately. The results showed that the gear profile modification parameters thus given are so accurate and efficient that the impact on gear meshing can be avoided with the dynamic fluctuation of transmission error of spur gears decreased greatly. A new way to the R&D and design of noiseless gears is thus proposed. References | Related Articles | Metrics

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Optimal layout design of cutters on tunnel boring machine Su, Peng-Cheng (1); Wang, Wan-Shan (1); Huo, Jun-Zhou (2); Li, Zhen (2) 2010, 31 (6):  877-881.  DOI: - Abstract ( 309 )   HTML   PDF (1361KB) ( 826 )   The layout design of cutters on cutter head of a full-face rock tunnel boring machine (TBM) is a key problem for the design of rock TBM. The principle of equilibrium of spatial forces should be satisfied for the cutter head under the action of forces, thus developing a nonlinear multiobjective layout model of cutters. Then, a co-evolutionary algorithm is proposed to optimize the layout of cutters. Exemplifying the TBM used in the water tunnel project for Taohe River, its layout of cutters was compared with that based on the model developed and the algorithm proposed for verification. The results showed that under the conditions that the rock boundaries are variable the model and algorithm as above are both feasible and effective, by which the layout of cutters is available to get smaller upsetting moment and unbalanced forces. References | Related Articles | Metrics

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ADAMS-based optimal design of tunnel boring machine's cutter head Cheng, Jun (1); Gong, Ya-Dong (1); Chen, Tao (1); Chen, Xiao-Gang (1) 2010, 31 (6):  882-885.  DOI: - Abstract ( 333 )   HTML   PDF (374KB) ( 669 )   The rock-broken mechanism during the operation of the cutter head of TBM(tunnel boring machine) was analyzed to study the layout of cutters. A model of the cutters under the action of forces during TBM's working was therefore developed, thus proposing a scheme to improve the rock breakability of TBM's cutter head on which the cutters are lay out. Then, a nonlinear multi-objective mathematical model with complex constraints was developed, with an optimization program provided via an intelligent algorithm for the layout design of cutters on the tunnel shield/cutter head of a TBM. Exemplifying the cutter head of an EPB6.28 TBM, an optimized design was given to set up a prototype with digitized cutter head, to which a simulation was done for the verification of equilibrium of forces. Comparing analytically the cutter wear and equilibrium of forces between a previous and a newly designed cutter heads, the results showed digitally that the new one is more practicable than the previous one. References | Related Articles | Metrics

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Testing investigation on the reduction/magnetic separation of oxide ore from Bayan Obo Gao, Peng (1); Han, Yue-Xin (1); Li, Yan-Jun (1); Sun, Yong-Sheng (1) 2010, 31 (6):  886-889.  DOI: - Abstract ( 275 )   HTML   PDF (578KB) ( 907 )   The reduced oxide ore from Bayan Obo with high metallization rate was obtained via a high-efficiency reduction process, then the efficient concentrations of such metal elements as Fe, Nb and RE were implemented. The reduced ore with metallization rate up to 94.48% was obtained by optimizing the operation parameters in tests such as reducing temperature/time and carbon ratio, and, after stepped grinding and grain-size separation, the Fe grade 91.61%, metallization rate 93.79% and Fe recovery rate 93.23% were obtained as the starting material for steel-making. In the tailings the REO is 12.25% with recovery rate 98.73%, i.e. available to be the raw material for RE beneficiation. References | Related Articles | Metrics

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Fault tree analysis of tailing dam break due to overtopping Wei, Yong (1); Xu, Kai-Li (1); Zheng, Xin (1) 2010, 31 (6):  890-893.  DOI: - Abstract ( 293 )   HTML   PDF (384KB) ( 540 )   Based on several typical cases of tailing dam break during flood periods, the basic events relevant to the accidents of tailing dam break due to overtopping were clarified and generalized, such as seismic intensity beyond the designed value and ineffective flood discharging measures taken. The accidents of tailing dam break due to overtopping were studied introducing fault tree analysis including minimum cut sets, minimum path sets and structural importance. The results showed that the number of minimum cut sets that causes the accidents of tailing dam break due to overtopping is 54, thus revealing that such accidents are easy to take place; the number of minimum path sets that implies the prevention of such accidents is 4; and the calculated structural importance of relevant basic events means that hidden danger, poor design and inferior construction of dam, lack of routine maintenance and poor geological conditions, etc, all are crucial to the control and prevention of such accidents especially during flood periods. References | Related Articles | Metrics

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Mechanical analysis and construction process of bridge reinforcement via additional RC with bars and steel fibres Zhang, Wen-Xian (1); Luo, Bing (2); Chen, Cheng (1); Han, Zhi-Hui (1) 2010, 31 (6):  894-897.  DOI: - Abstract ( 226 )   HTML   PDF (1329KB) ( 548 )   After the operation of the Northern Bridge in Dongguan, such troubles as seepage and openings were found at the deck slabs wet-jointed between T-beams. For such troubles, the additional RC paving reinforcement with both steel fibres and bars is regarded as highly applicable to the bridge. Investigates the parameters and construction process relevant to the method of reinforcement. The numerical software MIDAS-Civil was thus used to model the mechanical behavior of the bridge. The interconnection between the new and existing concrete bridge structures was simulated taking account of the overload and shrinkage creep of concrete. The spacing between anchoring bars and optimal thickness of concrete bridge deck were then given. Assuming that the microcracks are continuous and hinged joints, a conclusion is drawn that getting rid of the existing deck slab cast in site, which was the source of the troubles as above, the bridge will be improved greatly. The construction process as a way to reinforce the bridge has been accepted successfully to use. References | Related Articles | Metrics

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A multi-attribute decision-making method based on advantages of sequential alternatives with incomplete information Pan, Yu-Hou (1); Zhang, Fa-Ming (2); Guo, Ya-Jun (1); Ren, Xiao-Yu (1) 2010, 31 (6):  898-901.  DOI: - Abstract ( 327 )   HTML   PDF (1638KB) ( 534 )   In case that the information on weight and attribute are both completely unknown and the decision-makers can only sequence all the alternatives in accordance to the same index, a rapid decision-making method is proposed at the low cost. An idea named the number of sequential advantage is presented, then the virtual attribute values are formed, which don't affect the sequenced results. With the virtual attribute values used, a method to approximate to ideal points(TOPSIS) is applied to framing the weight of virtual decision-making index, and the values in all alternatives are aggregated and sequenced via the virtual attribute values and the weight. A numerical example is given to verify the effectiveness of the method proposed. References | Related Articles | Metrics

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Combination forecast based on experts' rational expectation method and its application Yu, Zhen-Ming (1); Guo, Ya-Jun (1); Yang, Zheng (1); Hou, Fang (1) 2010, 31 (6):  902-905.  DOI: - Abstract ( 309 )   HTML   PDF (946KB) ( 523 )   Combinating several forecast models of a single object together is an efficient way to improve the precision in forecast. Every forecast model of a single object in the combination is evaluated comprehensively, in views of experts' rational expectation, on its adequacy of fit models, method complexity in application, compatibility and time dependency. Then, a combination weight coefficient is set up so as to form a combination forecast method characterized by subjective information integrated with objective information. Comparing the combination model with the models of single object analytically, a forecast is made for the quantity of private cars in China with an analysis made to the forecast. The results reveal that the former is superior to the latter in adaptability with precision improved greatly. References | Related Articles | Metrics

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The automorphism group of a class of simple Lie algebra Liu, Jian-Bo (1); Wang, Xin-Xin (1); Zhang, Yan-Yan (1) 2010, 31 (6):  906-908.  DOI: - Abstract ( 247 )   HTML   PDF (125KB) ( 963 )   Based on the study on the automorphisms and anti-automorphisms of a class of simply associative q-quantum tori and analyzing the matrices related to them, a conclusion is drawn that there are only two classes of matrices related to the automorphisms, while no anti-automorphism is found when p≠2 and only two classes of matrices related to the anti-automorphisms when p=2 as well. Therefore, the automorphisms and anti-automorphisms of such a class of simply associative algebra are determined and, consequently, the automorphism group of Lie algebra related to the class of q-quantum tori is determined. References | Related Articles | Metrics

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Properties and mechanism of a compound scale inhibitor Wang, Xian-Ge (1); Qi, Wei-Wei (1); Zhang, Xing-Wen (2); Sun, Ting (1) 2010, 31 (6):  909-912.  DOI: - Abstract ( 267 )   HTML   PDF (1362KB) ( 664 )   Static experiments were carried out to validate the performance of a compound scale inhibitor, that is composed of the polyepoxysuccinic acid (PESA), polyaspartic acid (PASP) and acrylic-2-acrylamide-2-methylpropane sulfonic acid copolymer (AA/AMPS). Its scale inhibiting mechanism was discussed with SEM. The experimental results showed that the compound scale inhibitor has favorable properties of scale inhibition for CaCO3, CaSO4 and Fe2O3 in comparison with the imported scale inhibitors such as MDC220 and PTP-0100. The effects of hardness and alkalinity of water on the scale inhibition rates of the compound scale inhibitor are comparatively low. SEM images of CaCO3 and CaSO4 crystals indicated that the inhibitor causes the crystal lattice of scale to be distorted, then the regularly dense crystal structure transforms into amorphous state. References | Related Articles | Metrics