2025-04-09 2005, Volume 12 Issue 5

  • Select all
  • Kun Yu , Wen-xian Li , Ri-chu Wang

    Studies on the mechanical properties and microstructures of as-cast and extruded Mg-Ce-Zn-Zr and Mg-Nd-Zn-Zr alloys have been made before and after heat treatment. The results show that the mechanical properties of as-cast Mg-Ce and Mg-Nd alloys are as good as those of typical die cast AZ91 alloy and the heat resistant WE43 alloy. In Nd-containing alloys, the precipitated phase Mg12 Nd contributes significantly to age hardening. The mechanical properties of extruded alloys are improved obviously compared with those of as-cast alloys. The ultimate strength is 257.8 MPa for extruded Mg-Ce alloy and 265.6 MPa for extruded Mg-Nd alloy. Extrusion is a useful method to improve both the strengths and elongations of the two experimental alloys at both ambient and elevated temperatures. The grain refinement and precipitation strengthening are the main strengthening mechanisms in the alloys. Tensile fracture surfaces show a dimple pattern after extruding and therefore reflect an improved elongation.

  • Dun-qiang Tan , Wen-xian Li , Yu-de Xiao , Lang Zhou , Wei Chen

    FVS1212/FVS0812 material was prepared by adding FVS1212 powder into FVS0812 powder. The structure and mechanical properties of materials were studied by means of X-Ray, tensile measurement, OM and SEM. The results show that adding proper content FVS1212 powders can improve the tensile strength of FVS0812 aluminum at room temperature and elevated temperature, and that the elongation of FVS1212/FVS0812 material is better than that of FVS1212 aluminum.

  • Li-ping Yu , Han-ning Xiao , Peng-fei Hu

    SiO2-Al2O3-ZrO2 glasses with different nucleating agents were crystallized under special processing schedule. The microstructure and mechanical properties of the glass-ceramics in SiO2-Al2O3-ZrO2 system were investigated by differential scanning calorimetry, scanning electron microscopy, X-ray diffraction and three-point bending method. The results show that ZrO2 is not an effective nucleating agent in SiO2-Al2O3-ZrO2 system, while TiO2 is effective for the separation of spinel, and P2O5 facilitates solubility of ZrO2 in glass and crystallization. The main crystalline phases of the glass-ceramics are spinel, anorthite and tetragonal zirconia. With the increase of ZrO2 content in the glass, glass-ceramics show higher bending strength (120 MPa) than others.

  • Feng He , Feng Niu , Guang-hui Lou

    ZrO2 was added into CaO-Al2O3-SiO2 glass-ceramics and the effect of ZrO2 on sintering and crystallization of CaO-Al2O3-SiO2 glass ceramics was investigated. The results show that the sintering shrinkage ratio of glass particles decreases with the increase of the content of ZrO2. ZrO2 has an unfavourable effect on sintering shrinkage ratio of glass particles. The sintering shrinkage ratio of glass particles increases with the increase of sintering temperature. The increase of sintering temperature favors the decrease of the liquid phase viscosity of glass particles. ZrO2 has little effect on crystallization of main crystalline phase (β-wollastonite). However, it promotes the crystallization at relatively low temperature.

  • Chang-qing Xia , Yin-na Wang , An-ru Wu , Yi Gu

    ZK60-xcerium alloys were studied, where x mass fraction is 0, 0.52%, 0.94%, 1.51% and 1.98%, respectively. Influence of Ce contents and heat-treatment on microstructure and tensile properties was analyzed. The results show that cast ZK60 alloy containing no Ce has coarse crystal grains, and lots of segregation aggregates around the grain-boundary. However, the alloys containing Ce have refined grains, and grain-boundaries are purified at the same time. Obvious dynamic recrystallization occurs in tested alloys after hot-extrusion. Tensile strength heightens with the increase of Ce content, and grows higher after aging at 150 °C for 0–24 h (T5 treatment). Comparing tensile properties of investigated alloys in different states, it can be concluded that synthetical properties of the alloy with 1.51% Ce addition is the best of all. In extruded state, σb and δ of this alloy are 318.6 MPa and 14.4%, respectively. After aging for 24 h, σb is 338.6 MPa and δ is 15.6%.

  • An-xian Lu , Xue Li , Na Lin

    B2O3-BaO-ZnO glass was prepared by using conventional melt quenching technology. The forming regularity and the relationship between the composition and the property of B2O3- BaO - ZnO glass were investigated. The results show that the composition range for forming B2O3 - BaO -ZnO glass is very wide, but the content of B2O3 has a limit within mole fraction of 25%–75%. When the content of B2O3 is over the limit, the melt will be divided into two phases with different compositions and structures, whereas too low content of B2O3 will result in the crystallization of the melt during the cooling process. The thermal expansion coefficient, the transition temperature and the resistivity of the glass at room temperature are (5–10) × 10−6°C−1, 480–620 °C and (1.5–3.0)×1010 Θ · m, respectively.

  • Jin-lan Xia , Chun Wang , Zhen-yuan Nie , An-an Peng , Xin Guan

    The structure, properties and application to water-soluble coatings of a new complex antimicrobial agent Ag-carboxylmethyl citosan-thiabendazole (Ag-CMCTS-TBZ) prepared from different materiel ratios were reported. The silver ions were preferably coordinated with the free — NH2 groups and the — OH groups of secondary alcohol and carboxyl in CMCTS. TBZ preferably bonded to carboxyl group in CMCTS by electrostatic force and hydrogen bonding. Increase in silver ions content in the complex agent improved to some limited extent the antibacterial activity, but enhanced coloring and cost of the complex agent. Increase in TBZ content resulted in increase of antifungal activity, but decrease of water solubility of the complex agent. The antimicrobial MICs of the complex agent to Esherichia coli, Staphylococcus aureus, Candida albicans, Aspergillus niger, Mucor sp. were 20 – 80, 15 – 60, 20 – 55, 40 – 250, and 400 – 1700 mg/kg, respectively. Addition of 0.1% of this complex agent to acrylic emulsion paint made the paint without substantial change in color, luster, viscosity, odor or pH value, but with an excellent and chronically persisting broad-spectra antimicrobial activity.

  • Xiao-hui Fan , Xu-ling Chen , Tao Jiang , Tao Li

    In order to optimize the sintering process, a real-time operation guide system with artificial intelligence was developed, mainly including the data acquisition online subsystem, the sinter chemical composition controller, the sintering process state controller, and the abnormal conditions diagnosis subsystem. Knowledge base of the sintering process controlling was constructed, and inference engine of the system was established. Sinter chemical compositions were controlled by the strategies of self-adaptive prediction, internal optimization and center on basicity. And the state of sintering was stabilized centering on permeability. In order to meet the needs of process change and make the system clear, the system has learning ability and explanation function. The software of the system was developed in Visual C++ programming language. The application of the system shows that the hitting accuracy of sinter compositions and burning through point prediction are more than 85%; the first-grade rate of sinter chemical composition, stability rate of burning through point and stability rate of sintering process are increased by 3%, 9% and 4%, respectively.

  • Xiao-lan Song , Peng Qu , Hai-pin Yang , Xi He , Guan-zhou Qiu

    Highly pure active γ-Al2O3 nanoparticles were synthesized from aluminum nitrate and ammonium carbonate with a little surfactant by chemical precipitation method. The factors affecting the synthesis process were studied. The properties of γ-Al2O3 nanoparticles were characterized by DTA, XRD, BET, TEM, laser granularity analysis and impurity content analysis. The results show that the amorphous precursor Al(OH)3 sols are produced by using 0.1 mol/L Al(NO3)3 · 9H2O and 0.16 mol/L (NH4)2CO3 · H2O reaction solutions, according to the volume ratio 1.33, adding 0.024% (volume fraction) surfactant PEG600, and reacting at 40 °C, 1 000 r/min stirring rate for 15 min. Then, after stabilizing for 24 h, the precursors were extracted and filtrated by vacuum, washed thoroughly with deionized water and dehydrated ethanol, dried in vacuum at 80°C for 8 h, final calcined at 800 °C for 1 h in the air, and high purity active γ-Al2O3 nanoparticles can be prepared with cubic in crystal system, OH7-FD3M in space group, about 9 nm in crystal grain size, about 20 nm in particle size and uniform size distribution, 131. 35 m2/g in BET specific surface area, 7 – 11 nm in pore diameter, and not lower than 99.93% in purity.

  • De-wen He , Yu-tang Xiao , Xiong Li , Yan Jin

    Polyethylene glycol (PEG) membranes with different molecular mass cut-offs were used to treat oil/water emulsion, and the effects of experimental conditions including pressure, temperature and different operating modes on permeate flux and removal rate of chemical oxygen demand (CODCr) were studied. The results show that the permeate flux of ultrafiltration membrane is influenced by pressure and temperature; practical pressure is chosen to be 0.3 – 0.7 MPa for the PEG with molecular mass cut-offs of 8 000 and 0.7 – 1.0 MPa for the PEG with molecular mass cut-offs of 2 500; and the practical temperature is chosen to be 25 – 32 °C. Different operating modes of ultrafiltration also influence the permeate flux and removal rate of CODCr. The ultrafiltration membrane of intermittent cross-flow operating mode is easier to be influenced by blocky polarization and contamination than that of sequential cross-flow operating mode. Removal rate of CODCr in intermittent cross-flow and sequential cross-flow condition can be maintained at about 93%.

  • Ke-jun Zhong , Wan-zhi Wei , Fang-qiu Guo , Lan-fang Huang

    The volatile and semi-volatile components in tobacco flavor additives were extracted by both simultaneous distillation extraction and solid-phase micro-extraction. Extraction conditions for solid-phase micro-extraction were optimized with information theory. Then, detection were accomplished by gas chromatography-mass spectrometry. Characteristic of each method was compared. Qualitative analysis and quantitative analysis of 6# tobacco flavor sample were accomplished through both simultaneous distillation extraction and solid-phase micro-extraction. The experimental results show that solid-phase micro-extraction method is the first choice for qualitative analysis and simultaneous distillation extraction is another good selection for quantitative analysis. By means of simultaneous distillation extraction, 20 components are identified, accounting for 92.77% of the total peak areas. Through solidphase micro-extraction, there are 17 components identified accounting for 91.49% of the total peak areas. The main aromatic components in 6# tobacco flavor sample are propanoic acid, 2-hydroxy-, ethyl ester, menthol and menthyl acetate. The presented method has been successfully used for quality control of tobacco flavor.

  • Hui Wang , Guo-hua Gu , Yun-feng Qi

    The crushing performance of printed circuit board (PCB) was studied on several crushers. The results show that PCB is a material which is difficult to crush. The crushing performance of PCB with disk crusher, especially vibration grinding, which has cut or impact action, excels that of jaw crusher or roller crusher. The PCB scrap is worthwhile to recycle using variety of modern characterization methods. When compared with natural resources, this material stream remains a rich precious metal and nonferrous metals. In PCB scrap, metals account for 47% of the total material composition, in which there exists 19.66% copper, 11.47% iron, 3.93% lead, 300 g/t gold and 5–10 kg/t silver, etc. In addition, the PCB scrap contains 27% of plastics and 26% of refractory oxides.

  • Xiao-qing Chen , qin Liu , xin-yu Jiang , fan Zeng

    The microwave-assisted method was used to extract polysaccharides from solanum nigrum. The optimum experimental parameters, mechanism of the extraction and the effect of microwave-assisted extraction process on the structures of polysaccharides were investigated. The extract was analyzed by the modified phenol-sulfuric acid method at 490 nm. The optimum experimental parameters were obtained by orthogonal experiments as follows: extraction time 15 min, microwave radiation power 455 W and the process ratio of materials mass to solvent volume 1:20. The results show that compared with the conventional reflux extraction, the microwave-assisted extraction has a higher yield in shorter time, with no effect on the finally obtained polysaccharides as seen from the FT-IR spectra. The scanning electron microscopy images reveal that the mechanism of the extraction is related to the structural changes of the plant cells in different extracting conditions.

  • Yong Zhang , Xin-guo Hu , Yu-wen Liu , Yu-shan Cheng

    Vanadium pentoxide xerogel (VXG) films were prepared by rapid quenching, then coin type 2016 size lithium rechargeable batteries were assembled and tested with the VXG film electrodes and lithium anodes. Electrochemical impedance spectroscopy (EIS) analysis result reveals the expected response for intercalation, except that there is almost no Warburg (diffusion) component. Analyses results of cyclic voltammetry (CV), constant discharge (CD) and discharge-charge(DC) indicate that the sample achieves a high initial discharge specific capacity of approximate 400 mA · h/g and a corresponding efficiency of 97 % in the voltage diapason of 1.5–4.0 V with a draining current of 60 mA/g. Its preservation ratio of capacity still keeps as high as 85 % even after 100 cycles. The good electrochemical performance indicates that VXG film material is a promising cathode for lithium rechargeable batteries.

  • Jun-hui Li , Si-zong Min , Lei Han , Jue Zhong

    The transmitting models of ultrasonic vibration in ultrasonic transducer and capillary were presented according to the propagating mechanism of ultrasonic wave in elastic body. The coupling characteristics of ultrasonic longitudinal-complex transverse vibration system were simulated by Matlab software. The ultrasonic vibration displacement and the velocity of high frequency were measured by using the PSV-400-M2 (1.5 MHz) laser Doppler vibrometer. The vibration locus shapes driven by the same frequency and different frequencies were tested by using GDS-820S dual channel digital oscilloscope. The microstructures at bonding interface were observed by means of KYKY2800 scanning electron microscope. The results show that ultrasonic vibration displacement or velocity and energy density increase with the decrease of section area in the transmitting process. The vibration locus shapes driven simultaneously by the same frequency and different frequencies are elliptical (or circular) loci and rectangular (or square) loci, respectively. And the characteristics at bonding interface are improved by coupling loci.

  • Zhi-gang Chen , Bi-qing Zeng , Ce Xiong , Xiao-heng Deng , Zhi-wen Zeng , An-feng Liu

    A new file assignment strategy of parallel I/O, which is named heuristic file sorted assignment algorithm was proposed on cluster computing system. Based on the load balancing, it assigns the files to the same disk according to the similar service time. Firstly, the files were sorted and stored at the set I in descending order in terms of their service time, then one disk of cluster node was selected randomly when the files were to be assigned, and at last the continuous files were taken orderly from the set I to the disk until the disk reached its load maximum. The experimental results show that the new strategy improves the performance by 20.2% when the load of the system is light and by 31.6% when the load is heavy. And the higher the data access rate, the more evident the improvement of the performance obtained by the heuristic file sorted assignment algorithm.

  • Guang Li , Min Wu

    A mathematical model was developed combining the dynamics of an Euler-Bernoulli beam, described by the assumed-mode method and hydraulic circuit dynamics. Only one matrix, termed drive Jacobian, was needed in the modeling of interaction between hydraulic circuit and flexible manipulator mechanism. Furthermore, a new robust controller based on mentioned above dynamic model was also considered to regulate both flexural vibrations and rigid body motion. The proposed controller combined sliding mode and backstepping techniques to deal with the non-linear system with uncertainties. The sliding mode control was used to achieve an asymptotic joint angle and vibration regulation by providing a virtual force while the backstepping technique was used to regulate the spool position of a hydraulic valve to provide the required control force. Simulation results are presented to show the stabilizing effect and robustness of this control strategy.

  • Chu-da Liu , De-pei Qian , Yi Liu , Yan-ping Li , Kai-ping Xiao

    A framework for end-to-end RSVP context transfer in Mobile IPv6 (MIPv6) based on the architecture of F-HMIPv6 is proposed in this paper. The scheme provides an end-to-end RSVP context transfer for real-time applications to overcome the weakness of Context Transfer Protocol which can not meet the need of end-to-end QoS mechanisms because contexts are only transferred between Access Routers (ARs), therefore they can promptly get the same forwarding process, minimize the handover service disruption, and avoid initiating the end-to-end RSVP signaling from scratch after an MN performs handovers. It may also reduce the signaling overhead and handover latencies by adopting the F-HMIPv6architecture. The performance of the approach is compared with the re-initiating RSVP signaling to re-establish QoS states using network simulator, and the numerical results show that the scheme has the less latency and packet loss than that of the re-initiating approach.

  • Wei-min Zhong , Dao-ying Pi , You-xian Sun

    A support vector machine with guadratic polynomial kernel function based nonlinear model multi-step-a-head optimizing predictive controller was presented. A support vector machine based predictive model was established by black-box identification. And a quadratic objective function with receding horizon was selected to obtain the controller output. By solving a nonlinear optimization problem with equality constraint of model output and boundary constraint of controller output using Nelder-Mead simplex direct search method, a sub-optimal control law was achieved in feature space. The effect of the controller was demonstrated on a recognized benchmark problem and a continuous-stirred tank reactor. The simulation results show that the multi-step-ahead predictive controller can be well applied to nonlinear system, with better performance in following reference trajectory and disturbance-rejection.

  • Ying-li Gao , Shi-qiong Zhou

    Hydration shrinkage generated by cement hydration is the cause of autogenous shrinkage of high strength concrete. It may result in the volume change and even cracking of mortar and concrete. According to the data analysis in a series of experimental studies, the influence of ultra-fine fly ash on the hydration shrinkage of composite cementitious materials was investigated. It is found that ultra-fine fly ash can reduce the hydration shrinkage of cement paste effectively, and the more the ultra-fine fly ash, the less the hydration shrinkage. Compared with cement paste without the ultra-fine fly ash, the shrinkage ratio of cement paste reduces from 23.4% to 39.7% when the ultra-fine fly ash replaces cement from 20% to 50%. Moreover, the microscopic mechanism of the ultra-fine fly ash restraining the hydration shrinkage was also studied by scanning electron microscopy, X-ray diffraction and hydrated equations. The results show that the hydration shrinkage can be restrained to a certain degree because the ultra-fine fly ash does not participate in the hydration at the early stage and the secondary hydration products are different at the later stage.

  • Ji-xian Huang , Guang-shu Bao , Qing-song Li

    The characteristic of geographic information system (GIS) spatial data operation is that query is much more frequent than insertion and deletion, and a new hybrid spatial clustering method used to build R-tree for GIS spatial data was proposed in this paper. According to the aggregation of clustering method, R-tree was used to construct rules and specialty of spatial data. HCR-tree was the R-tree built with HCR algorithm. To test the efficiency of HCR algorithm, it was applied not only to the data organization of static R-tree but also to the nodes splitting of dynamic R-tree. The results show that R-tree with HCR has some advantages such as higher searching efficiency, less disk accesses and so on.

  • Huai-sheng Peng , Jian Deng , De-sheng Gu

    A new method was proposed to cope with the earth slope reliability problem under seismic loadings. The algorithm integrates the concepts of artificial neural network, the first order second moment reliability method and the deterministic stability analysis method of earth slope. The performance function and its derivatives in slope stability analysis under seismic loadings were approximated by a trained multi-layer feed-forward neural network with differentiable transfer functions. The statistical moments calculated from the performance function values and the corresponding gradients using neural network were then used in the first order second moment method for the calculation of the reliability index in slope safety analysis. Two earth slope examples were presented for illustrating the applicability of the proposed approach. The new method is effective in slope reliability analysis. And it has potential application to other reliability problems of complicated engineering structure with a considerably large number of random variables.

  • Xue-bin Wang

    The distributed shear stress and the displacement across shear band, the evolution of plastic zones, and the load-carrying capacity of rock specimen were investigated in plane strain direct shear test according to Fast Lagrangian Analysis of Continua (FLAC). And then the shear displacement distribution in normal direction of system composed of localized shear band and elastic rock was analyzed based on gradient-dependent plasticity. The adopted failure criterion was a composite of Mohr-Coulomb criterion, that is, the relation between tension cut-off and post-peak constitutive of rock was linear strain-softening. Numerical results show that shear stress field approximately undergoes three different stages. At first, shear stress is only concentrated in the middle of top and base of specimen. Next, shear stress in the middle of specimen tends to increase, owing to superposition of shear stresses. Interestingly, two peaks of shear stress appear far from the loading ends of specimen, and the peaks approach with the increase in timestep until elements at the center of specimen yield. Finally, relatively lower shear stress level is reached in large part of specimen except in the regions near the two ends. As flow stress decreases, the analytical shear displacement distribution in shear band based on gradient-dependent plasticity becomes steep; outside the band, it is linear and its slope tends to decrease. These theoretical results qualitatively agree with that of the present numerical predicted results. Main advantage of the analytical solution over the numerical results according to FLAC is that it is continuous, smooth and non-linear (except at elastic stage).

  • Yu-jun Zuo , Xi-bing Li , Zi-long Zhou

    The ejection velocity of rock fragments during rock burst, one of the important indexes representing the rock burst strength, is used most conveniently in the supporting design of tunnel with rock burst tendency and is often determined by means of observation devices. In order to calculate the average ejection velocity of rock fragments theoretically, the energy of rock burst was divided into damage consuming energy and kinetic energy gained by unit volume of rock firstly, and then the rock burst kinetic proportional coefficient ν was brought up which could be determined according to the rock-burst damage energy index WD, at last the expression of the average ejection velocity of rock fragments during rock burst was obtained and one deep level underground tunnel was researched using the mentioned method. The results show that the calculation method is valid with or without considering the tectonic stress of tunnels, and that the method can be a reference for supporting design of deep mining.

  • Qi-jie Wang , Xin-hao Liao , Yong-hong Zhou , Zheng-rong Zou , Jian-jun Zhu , Yue Peng

    The grey forecasting model has been successfully applied to many fields. However, the precision of GM(1,1) model is not high. In order to remove the seasonal fluctuations in monitoring series before building GM (1,1) model, the forecasting series of GM(1,1) was built, and an inverse process was used to resume the seasonal fluctuations. Two deseasonalization methods were presented, i.e., seasonal index-based deseasonalization and standard normal distribution-based deseasonalization. They were combined with the GM(1,1) model to form hybrid grey models. A simple but practical method to further improve the forecasting results was also suggested. For comparison, a conventional periodic function model was investigated. The concept and algorithms were tested with four years monthly monitoring data. The results show that on the whole the seasonal index-GM(1,1) model outperform the conventional periodic function model and the conventional periodic function model outperform the SND-GM(1,1) model. The mean absolute error and mean square error of seasonal index-GM(1,1) are 30.69% and 54.53% smaller than that of conventional periodic function model, respectively. The high accuracy, straightforward and easy implementation natures of the proposed hybrid seasonal index-grey model make it a powerful analysis technique for seasonal monitoring series.