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15 May 2005, Volume 26 Issue 5 Previous Issue    Next Issue
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Analysis and modeling of networked control systems based on descriptor system Qiu, Zhan-Zhi (1); Zhang, Qing-Ling (1); Yang, Chun-Yu (1) 2005, 26 (5):  409-412.  DOI: - Abstract ( 225 )   HTML   PDF (249KB) ( 804 )   Based on a regular, impulse-free and linear time-invariant descriptor system, the characteristics of multiple input/output networked control systems with distributed time-delay and dynamic output feedback controller are analyzed when sensors and the controller are clock-driven but asynchronous-sampling and actuators are event-driven. Then, a mathematic model is developed for the networked control system under which control object plays a role of regular and impulse-free descriptor system. A controlled example of electric power system is given as linear descriptor system model, which shows that the way of modeling is valid. The result is useful to the analysis and design of networked control systems under which the controlled object plays a role of linear descriptor system. References | Related Articles | Metrics

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Coordinate mapping of brain surgery robot system based on vision localization Pan, Feng (1); Wu, Wei (2); Yang, Yi-Lu (2); Xu, Xin-He (2) 2005, 26 (5):  413-416.  DOI: - Abstract ( 235 )   HTML   PDF (251KB) ( 961 )   The architecture and surgical operation process of a brain surgery robot system based on vision localization technology is expounded to discuss in depth the mapping relations among four coordinates. Computer vision, robot and 3D-medical imaging reconstructing technology are combined together to help surgeons to complete brain's surgical operation. Marker registration method is adopted in robot system with vision localization instead of passive machine arm localization so as to improve greatly the exactness in operation as well as the intellectualization level. The mapping relations among each and every coordinate are thus studied further to work out the calibration of surgical operation actions and relevant planning. As a result, the robot realizes the planning posture. A theoretical foundation is therefore provided for practice. References | Related Articles | Metrics

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Locating-pricing game of duopoly enterprises at different costs Liu, Yan-Chun (1); Gao, Li-Qun (1) 2005, 26 (5):  417-420.  DOI: - Abstract ( 211 )   HTML   PDF (1077KB) ( 1074 )   Aiming at the problem that the traditional Hotelling segmentation model was assumed that the production costs of duopoly enterprises are completely the same, with the two-phase gaming model applied to it, a locating-pricing model is proposed for both enterprises at different costs. The results show that when the difference the products of the same quality supplied by the duopoly enterprises is maximized, the enterprise which is superior in cost to the other one will gain more excess profit though both can gain profit. However, when the difference is minimized, the enterprise superior in cost will be dominant on market and the inferior one has to fall far behind the former even retreat from the market. References | Related Articles | Metrics

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Multicast mechanism based on CHMMP in mobile wireless Internet Wang, Xing-Wei (1); Song, Bo (1); Sun, Xue-Bo (1); Huang, Min (2) 2005, 26 (5):  421-424.  DOI: - Abstract ( 221 )   HTML   PDF (179KB) ( 414 )   Based on CHMMP (Combined Hierarchical Mobility Management Protocol), a multicast mechanism was developed for application in mobile wireless Internet. According to CHMMP, the MH (Mobile Host) doesn't need registration with its home agent when it hands over within the same foreign area. Compared with the bi-directional tunnel and remote subscription in accordance to IETF mobile IP, the proposed mechanism can reduce not only the multicast tree maintenance overhead due to handover of multicast, but also the time delay handover registration. Simulation results showed that it could support efficiently group applications in mobile wireless Internet. References | Related Articles | Metrics

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On the SR-RM scheduling algorithm Wang, Xiao-Ying (1); Zhao, Hai (1); Zhang, Wen-Bo (1); Yin, Zhen-Yu (1) 2005, 26 (5):  425-428.  DOI: - Abstract ( 280 )   HTML   PDF (159KB) ( 650 )   Analyzing the advantages of RM (Rate Monotonic) scheduling algorithm and its disadvantages in actual execution, the SR-RM (Self-Regulating Rate Monotonic) scheduling algorithm is proposed to adjust the task execution period through tracking the actual execution time of assigned tasks and processor utilization. In addition, SR-RM engaged in decrease unscheduled task set to improve reliability through scout and predict environment transformation. Simulation tests revealed that SR-RM scheduling algorithm is available to the real-time implementation environment of reducing the miss rate of tasks with higher processor utilization. References | Related Articles | Metrics

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Acoustics-based model for spotting exactly points of impact of bombs/shells Chen, Dong-Ming (1); Chang, Gui-Ran (2); Gao, Xiao-Xing (1) 2005, 26 (5):  429-432.  DOI: - Abstract ( 246 )   HTML   PDF (166KB) ( 596 )   An acoustics-based mathematic model is developed to detect exactly the points of impact of bombs/shells. Receiving detonation sound wave signal by acoustics sensors to get the relative time data of sonic transmission and taking account of the effects of background noise, temperature, humidity, and wind speed/direction on detonation sound wave. The model can be used to calculate the exact position of a point of impact rapidly. Then, the result is sent to the command control post automatically as reference for calibration to modify firing data. The whole service practice firing shooting can thus be evaluated scientifically and precisely. As proved by actual spotting verification, the model is regarded as exact and effective in improving the efficiency of military drill, with expenses reduced greatly. References | Related Articles | Metrics

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Crystallization of amorphous Fe78Si9B13 alloy irradiated by CO2 laser Chen, Sui-Yuan (1); Liu, Chang-Sheng (1); Tan, Yong (1); Zhang, Xiao-Bin (1) 2005, 26 (5):  433-436.  DOI: - Abstract ( 232 )   HTML   PDF (184KB) ( 749 )   The amorphous Fe78Si9B13 alloy was partially crystallized when it was irradiated by CO2 laser beam with 20 mm spot diameter for 20 sec at 250 W and 300 W as the laser power. The microstructures of the original amorphous Fe78Si9B13 samples and that of the crystallized samples were all analyzed by means of Mossbauer spectrum, XRD and SEM. The results showed that the amorphous Fe78Si9B13 alloy can be crystallized by 6% and 9% in α-Fe(Si) phase at 250 W and 300 W, respectively. It was found that a textural phenomenon takes place in samples, and a massive amount of grains were precipitated along (200) crystal face. The phase crystallized by laser beam forms in the crystallized surface layers of the amorphous Fe78Si9B13 alloy. Under otherwise definite conditions, the crystallized portion increases with increasing laser power. References | Related Articles | Metrics

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Microstructural evolution of the semi-solid ZL201 alloy during remelting Wang, Ping (1); Kang, Hao (1); Lu, Gui-Min (1); Cui, Jian-Zhong (1) 2005, 26 (5):  437-439.  DOI: - Abstract ( 177 )   HTML   PDF (182KB) ( 487 )   The microstructural evolution nearby-liquidus semi-continuous casting ZL201 aluminum alloy during remelting was studied by means of electron microscope and image analyzer. The results showed that a thixotropic microstructure liable to form semi-solid metal is obtained when the alloy is remelted at 620°C - 630°C then held for 5 min - 10 min. Under such conditions, the average equal-area-circle grain diameter is 43.8 μm with average roundness 1.87. An ideal semi-solid or paste-like ZL201 Al-alloy is thus obtained through nearby liquidus semi-continuous casting. References | Related Articles | Metrics

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Finite element simulation of remelting temperature fields of semi-solid A356 alloy Liu, Jing (1); Dong, Li-Na (1); Han, Yi (2); Wang, Ping (2) 2005, 26 (5):  440-443.  DOI: - Abstract ( 182 )   HTML   PDF (196KB) ( 485 )   The remelting temperature field of semi-solid A356 alloy was simulated using ANSYS software. The result showed that the current density of coil is inversely proportional to heating time and directly proportional to the temperature difference between specimen's inside and outside. The appropriate current density is 0.5 × 107 A/m2 and 0.6 × 107 A/m2 when the cross-sectional area of the coil used is 40 mm × 130 mm, and the temperature difference is 8.6°C and 9.8°C with heating time 31 min and 21 min, respectively. The appropriate current density is 0.80 × 107 A/m2 and 0.85 × 107 A/m2 when the cross-sectional area of the coil used is 20 mm × 130 mm, and the temperature difference is 8.7°C and 9.0°C with heating time 33 min and 30 min, respectively. The simulation provides theoretically a guidance for the industrial practice of semi-solid of A356 alloy. References | Related Articles | Metrics

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Effect of frequency of LF electromagnetic field on microstructures of semi-continuously cast high-strength Al alloy Yan, Ying (1); Zhang, Cai-Bei (1); Cui, Jing-Lei (1); Cui, Jian-Zhong (2) 2005, 26 (5):  444-447.  DOI: - Abstract ( 213 )   HTML   PDF (236KB) ( 404 )   The effect of frequency of LF electromagnetic field on microstructure of Φ100 mm semi-continuously cast Al alloy ingot was investigated by metalloscope and TEM. The results show the grain size decreases somewhat, but number of equiaxial grains increases with a current 100 A at 15 Hz as compared with conventional ingot, grain refinement is found to be most obvious at 25 Hz. But grain size turns to increase then with increasing frequency. With a current 100 A at 25 Hz, the intergranular dislocation density becomes higher with smaller size of precipitates which are mainly granular η', η and lamellar T phases and the precipitate-free zones on both sides of grain boundary are about 100 nm wide. However, the size of intergranular precipitates increases somewhat at 15 Hz, which are mainly lamellar or lath η, lamellar T and granular η' phases with precipitate-free zones about 300 nm wide. References | Related Articles | Metrics

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Preparation of Al-Mg-based semisolid alloy by inclined cooling/shearing Guan, Ren-Guo (1); Li, Jun-Peng (1); Shi, Lu (1); Wen, Jing-Lin (1) 2005, 26 (5):  448-451.  DOI: - Abstract ( 192 )   HTML   PDF (261KB) ( 888 )   An experimental inclined cooling/shearing set-up was developed to prepare the Al-Mg-based semisolid alloy, the molten alloy nucleated heterogeneously on the inclined-cooling plate surface and was sheared under the action of gravity force, and its microstructure gradually evolved into fine spherical grain from coarse equiaxed grain network. By controlling casting temperature in the range of 660-690°C, the semisolid slabs with good microstructure were obtained, with the feather crystal which are usually found the high-Mg alloy slabs conventionally improved greatly. The surface conditions of cooling plate obviously affects the alloy microstructure, i.e., fine microstructure can be obtained if the cooling plate has a clean surface that is rough to a certain degree. The inclination angle of cooling plate is preferable in the range of 40°-50°. References | Related Articles | Metrics

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Study on mechanical properties of Si-free TRIP steel Li, Zhuang (1); Wu, Di (1); Wang, Jia-Fu (1) 2005, 26 (5):  452-455.  DOI: - Abstract ( 252 )   HTML   PDF (293KB) ( 690 )   Bainite, ferrite and a large amount of stably retained austenite were obtained through austempering immediately after intercritical annealing of Si-free TRIP steel. The behaviour of TRIP (transformation-induced plasticity) effect was discussed through observing microstructure, analyzing fracture morphology and comparing it with the mechanical properties of high-Si TRIP steels. The results showed that Si-free TRIP steel has the excellent mechanical properties due to strain-induced martensite transformation which forms TRIP of retained austenite when it is strained, and its fracture morphology presents toughness characteristics. The tensile strength, total elongation and strength-ductility balance property of such Si-free TRIP steel all reach their maximum values (754 MPa, 36% and 27144 MPa%, respectively) when it is heated at 790°C and then held at 400° for 5 min. References | Related Articles | Metrics

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Engineering calculation method of residual strain for plate rolling process Hu, Xian-Lei (1); Zhao, Zhong (1); Qiu, Hong-Lei (1); Liu, Xiang-Hua (1) 2005, 26 (5):  456-459.  DOI: - Abstract ( 208 )   HTML   PDF (162KB) ( 658 )   For the plates containing not a few alloying elements the calculation error of rolling force sometimes reaches 30% or higher if the TMCP rolling regime is adopted. Based on the conventional model of resistance to deformation, the temperature is taken as a key influencing factor on the resistance to deformation, thus obtaining the temperature range affecting the residual strain. Then, the influence of residual strain on rolling force is analyzed so as to develop a relevant mathematical model for engineering calculation. Its on-line applications in Shougang Plate Rolling Mill proved that the resistance to deformation is calculated to the accuracy of 7% with the new model used. References | Related Articles | Metrics

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Bending model developed for levelling rollers Zhou, Cun-Long (1); Wang, Guo-Dong (1); Liu, Xiang-Hua (1); Qin, Jian-Ping (2) 2005, 26 (5):  460-462.  DOI: - Abstract ( 251 )   HTML   PDF (693KB) ( 964 )   On a roller leveler the deflection of a plate under the action of levelling rollers is assumed that the deflection is resulting from the forces exerted by both screw-down and bending roller. Based on the elastoplasticity theory of a beam, the bent plate is referred to as a bent beam with the entry intermesh also considered and, generally, about 80% of plate thickness is of plastically deformed layer and 5%-15% or the rest is regarded as due to the effect of bending roller. Different roller bending models are thus developed on beam deflection basis to solve quantitatively the bending of levelling rollers. The roller's bending calculated theoretically conforms with the set value, which reveals the practicality of those models. References | Related Articles | Metrics

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Element-free Galerkin method (EFGM): A new method to simulation of plate rolling Cui, Qing-Ling (1); Li, Chang-Sheng (1); Liu, Xiang-Hua (1); Wang, Guo-Dong (1) 2005, 26 (5):  463-466.  DOI: - Abstract ( 208 )   HTML   PDF (319KB) ( 656 )   Introduces the principle of the EFGM (Element-Free Galerkin Method) and its application to steady state rolling process of slightly compressible rigid-plastic materials. The penalty function algorithm is utilized to meet the requirements of essential boundary conditions because the shape function of EFGM fails to satisfy conditions. To improve the accuracy, the tensor product weight function which has rectangular influence domain is picked out. The background cell in FEM is taken as integral element, and different Gauss integration schemes are used for the interior of solution domain and its boundary. The validity and correctness of EFGM are verified by comparing the results of actual plate rolling with that calculated via Rigid-Plastic FEM and experimental data in earlier works. References | Related Articles | Metrics

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Oxygen transfer mechanism from refractory to molten steel and influencing factors on it Yu, Jing-Kun (1); Zhu, Qiang (1) 2005, 26 (5):  467-469.  DOI: - Abstract ( 194 )   HTML   PDF (598KB) ( 517 )   Based on phase equilibrium and thermodynamics, the oxygen transfer mechanism from refractory to molten steel and relevant influencing factors were studied. The results showed that the equilibrium partial pressure of O2 in closed pores due to decomposition of oxides in the refractory is much higher than that in molten steel which has been deoxidated to a high degree. The fact reveals what are the main influencing factors on the oxygen transfer from refractory to molten steel. In addition, according to what kind of the refractory used and its composition, the ability to transfer oxygen will be different from other refractories. The lower the oxygen content in molten steel, the more the oxygen transferring from refractory to molten steel and the components of decomposed. References | Related Articles | Metrics

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Effect of compactness of CaO clinker on its carbonation and hydration resistance Chen, Min (1); Wang, Nan (1); Yu, Jing-Kun (1); Wen, Tie-Guang (2) 2005, 26 (5):  470-473.  DOI: - Abstract ( 225 )   HTML   PDF (319KB) ( 1022 )   CaO clinkers of different compactnesses were carbonated at 700°C in CO2 atmosphere with the carbonation rate controlled by diffusion process, regardless of the difference between compactnesses. For the clinker of low compactness, the carbonation reaction occurred simultaneously both on surface and inside pores, and each CaO grain was surrounded by CaCO3 thus formed, in which microfissures were found. But for the high-compactness samples, carbonation reaction only occurred on surface, with a compact CaCO3 layer thus formed which was combined well with the substrate material. Hydration test result showed that the clinkers after carbonation could effectively improve the hydration resistance of the CaO clinkers of either low or high compactness. However, the carbonated low-compactness clinker is prone to breakage during hydration process. It is therefore concluded that only the compact CaO clinker with low apparent porosity is suitable to carbonation for improving its hydration resistance. References | Related Articles | Metrics

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Partner selection and optimization model in global manufacturing Dong, Wen-Hui (1); Gong, Ya-Dong (1); Wang, Wan-Shan (1) 2005, 26 (5):  474-477.  DOI: - Abstract ( 211 )   HTML   PDF (802KB) ( 649 )   Dynamic alliance and virtual enterprise (VE) are the main components of global manufacturing, of which the partner selection is a key problem in VE to the success of a project. A partner selection method or multi-objective optimization model is proposed including time, cost and risk as factors to evaluate and constraints on the project. A genetic algorithm is further developed to solve the problem. The performance of this algorithm is demonstrated by an example showing the R&D activities of a smoke detector, and the results reveal the effectiveness and efficiency of this algorithm. References | Related Articles | Metrics

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Design of cylindricity error virtual measuring instrument and application of openGL Zhang, Lei (1); Zhang, Yu-Nan (1); Yang, Xiu-Min (2) 2005, 26 (5):  478-480.  DOI: - Abstract ( 243 )   HTML   PDF (166KB) ( 734 )   Introduces the technique of virtual instrument and the software development platform LabWindows/CVI and discusses the basic principles and mathematical models for developing the cylindricity error virtual measuring instrument with the sampling technique involved. The probe-to-probe error separation method was adopted in design to lower greatly the mechanical precision required for the virtual measuring instrument. The conceptual design and an example of developed virtual measuring instrument are described, as well as the application of OpenGL to the virtual measuring instrument. The soft panel designed for the virtual measuring instrument can display a three-dimensional graph of cylindricity error, thus providing a basis on which the cause of the error and the way to control it are both available. References | Related Articles | Metrics

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Tooth profile optimization and kinematic simulation of double crank ring-plate-type pin-cycloidal gear planetary drive Jin, Ying-Li (1); He, Wei-Dong (2); Li, Li-Xing (2); Ding, Jin-Yuan (1) 2005, 26 (5):  481-483.  DOI: - Abstract ( 215 )   HTML   PDF (162KB) ( 571 )   Based on the Visual C++ 6.0, the design of tooth profile of the cycloidal gear is optimally programmed to improve its engaging condition, thus calculating the multi-mesh and tooth face contact conditions between the cycloid gear and ring-plate. A judgement is preliminarily made that the basic dimensions of reducer are reasonable. The design efficiency is improved to realize the calculation available to simulating analysis, which the traditional mechanical design cannot do. Taking advantages of the plentiful graphic API interface for the OpenGL, a kinematic simulation is carried out for the drive, by which the gear engagement in the planetary drive system can be displayed directly for observation. References | Related Articles | Metrics

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On the convection coefficient of incompressible fluid flows at varying velocity along vertical plane Sun, Zhi-Li (1); Yan, Ming (1); Li, Guo-Quan (2) 2005, 26 (5):  484-487.  DOI: - Abstract ( 454 )   HTML   PDF (307KB) ( 1580 )   Based on the boundary layer theory, the rules of the formation of both velocity and thermal boundary layers of an incompressible fluid flowing at zero initial velocity along a vertical plane under the action of gravity are discussed, of which the fluid is featured with a big Prandtl number and constant thermal property. Computing formulas of thickness of both velocity and thermal boundary layers are given. Then, based on these formulas the calculation method on the convective heat coefficient is discussed further with a mathematical expression derived in detail. Compared with the model that the fluid flows along a horizontal plane, both the velocity boundary layer and thermal layer become thicker and the convection heat transfer is less turbulent in short distance flow. Many problems of heat transfer in actual engineering can be simplified as the models that fluid flows along vertical plane under the action of gravity. Applying these formulas in the thermal analysis of the gearbox attached to an aeroengine, an accurate result was obtained. References | Related Articles | Metrics

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Particle swarm optimization with contracted ranges of both search space and velocity Chen, Bing-Rui (1); Feng, Xia-Ting (1) 2005, 26 (5):  488-491.  DOI: - Abstract ( 269 )   HTML   PDF (235KB) ( 1677 )   To improve further the performance of PSO (Particle Swarm Optimization), a modified PSO algorithm is proposed and called CSV-PSO algorithm. Based on the best fitness of the particles, the ranges of both search space and velocity of the particles are contracted dynamically with the evolution of particle swarm in CSV-PSO algorithm. To avoid the possible occurrence of stagnation phenomenon in the PSO algorithm, the re-initialization mechanism based on different search spaces is introduced in the CSV-PSO. Numerical examples show that it is of advantage to accelerating the algorithm's convergence and improving its calculation accuracy so as to contract appropriately the ranges of both search space and velocity of particles in evolutionary progress and the algorithm is easier for convergence, more accurate for calculation and more stable for running. References | Related Articles | Metrics

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Theoretical analysis of relation between strain and electrical conductivity of graphite concrete Wu, Xian (1); Wu, Bo (2); Tian, Jun (1); Tang, Chun-An (1) 2005, 26 (5):  492-495.  DOI: - Abstract ( 206 )   HTML   PDF (163KB) ( 761 )   Discusses the conduction mechanism of prism-shaped graphite concrete in view of the whole process of an axial loading test, as well as the method of analogy and damage to the concrete. Analyzes the reasons why the up-and-down trend as shown on the deformation modulus-strain relation curve conforms to that as shown on the conductivity-strain curve. In case a specimen is damaged, its electric field and force field both comply with Laplace equation, and their boundary conditions are also in accord with each other. It means that it is possible to draw an analogy between the two fields in the whole loading test process of the graphite concrete samples, i.e., the correctness of such an analogy is verified by the test. Like the deformation modulus, the electrical conductivity is such an eigenvalue of a material that will characterize well the damage and rupture process. References | Related Articles | Metrics

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Experimental investigation on performance of modified styrene-butadiene-styrene (SBS) polymer asphalt mixture Wang, Xiao-Chu (1); Zhu, Fu-Sheng (1); Wang, Yi-Peng (2) 2005, 26 (5):  496-499.  DOI: - Abstract ( 206 )   HTML   PDF (192KB) ( 758 )   More than 20 kinds of modified SBS asphalt mixtures were investigated experimentally to analyze comparatively their performances including moisture retentivity and high/low temperature performance. The results showed that the marshal testing stability of AC-20I mesograin asphalt mixture is higher than that of skid-resistance-layer asphalt mixture in general, but their moisture retentivities are much the same. The high/low temperature performance of the asphalt mixtures made from Liaohe substratum bitumen are better than others, and the overall performance of the asphalt mixture using finished bitumen as raw material is superior. References | Related Articles | Metrics

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Polymeric aluminum-calcium chloride: A new flocculant and its preparation and preliminary application Liu, Mei-Ying (1); Hu, Xiao-Min (2); Zhang, Xiu-Juan (1); Su, Yong-Bo (1) 2005, 26 (5):  500-503.  DOI: - Abstract ( 272 )   HTML   PDF (102KB) ( 558 )   Polymeric aluminum-calcium chloride was prepared as a new inorganic flocculant instead of the prevailing polymeric aluminum chloride by which the sludge formed in wastewater treatment process is poor in dehydration. The aluminum oxide and calcium carbonate were taken as its materials and its preparation was in accordance to the steps as follows: baking them at high temperature; acid-dissolution; polymerization and dehydration. The synthesizing conditions are studied particularly and the optimal experimental parameters are thus obtained, i.e., the optimum proportion of raw materials (Al2O3 : CaCO3) is 3 : 2; the optimum time for acid-dissolution is 3 h and higher baking temperature is helpful for the synthesis process. The preliminary application of the new flocculant to waste water treatment was proved successful, and its performance was also proved superior to the prevailing polymeric aluminum chloride. References | Related Articles | Metrics

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- - 2005, 26 (5):  504-507.  DOI: - Abstract ( 197 )   HTML   PDF (222KB) ( 644 )   - References | Related Articles | Metrics

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- - 2005, 26 (5):  508-510.  DOI: - Abstract ( 197 )   HTML   PDF (205KB) ( 659 )   - References | Related Articles | Metrics