The reactive process for Al/SiCP composite was studied. SiC particles were in-situ coated by the exothermal reaction of SiC-Ti powder compact in Al melt bath, and easily incorporated into Al melt. The detailed study was carried out to understand the microstructures of the reacted SiC particles. During the reaction and consequent mixing, the successive processes include in-situ coating on the reacted SiC particles, coat dissolution and SiCP splitting. The tensile mechanical properties of 6013Al/SiCP composite processed by the present technology showed that the reacted SiCP considerably reinforced the 6013 matrix.
By phenomenological analysis of warm compaction, it is found that, compared with the contribution of particle plastical deformation to densification of powder compact, the particle rearrangement is a dominant densification mechanism for powder warm compaction, and the plastical deformation of particles plays an important role in offering accommodating deformation for particle rearrangement and densifying powder compact at the final stage of pressing. In order to attain density gain as high as possible during warm compaction, six rules for designing warm-compacting powder mixtures were proposed in detail.
The electronic structures of pure V, Nb and Ta metals with bcc structure were determined by one-atom (OA) theory. According to the electronic structures of these metals, their potential curves, cohesive energies, lattice parameters, elasticity and the dependence of linear thermal expansion coefficients on temperature were calculated. The electronic structures and characteristic properties of these metals with fcc and hcp structures and liquid states were studied.
Nanometer 3Y-TZP/20%Al2O3 (mass fraction) composite powders prepared by the chemical coprecipitation method were pressureless sintered at 1550 °C for 2 h. Effects of calcining temperatures at 800 °C, 1 000 °C, and 1 200 °C on phase structure, relative density, and Vicker’s hardness of the sintered bodies were studied. The results show that 1 000 °C was the optimal calcining temperature, and the powder calcined was composed of tetragonal zirconia with the Scherrer crystalline size of 6.3nm. The relative density was up to 98.5% under pressureless sintering, and the sintered body was t-ZrO2 (without m-ZrO2)+α-Al2O3 with the average size of 0.4 µm.
The kinetics on the growth of T. ferroxidans in the presence of Cu(II) was studied using of series piezoelectric quartz crystal (SPQC). Arsenic ion inhibits the growth of T. ferrooxidans, which is consistent with the previous results by other measuring methods. This further demonstrates that the SPQC can monitor the chemical activity of T. ferrooxidans growth. Cupric ion accelerates the growth of T. ferrooxidans. The mechanism was discussed, i. e., copper promotes the protein enzyme of T. ferrooxidans, rusticyanin, to form over the range of cupric ion concentration studied. The reaction order of cupric ion in accelerating the bacterial growth is 0.067. The growth of T. ferrooxidans is dependent on temperature, the apparent reaction activation energy decreases from 25.56 kJ/mol to 18.32 kJ/mol because of the addition of 10 mg/L Cu(II) to the bacterial growth solution of pH 2.0 at initial inoculum of 10%.
The template effect controlling the structure and morphology of ultrafine particles was described. Ni(OH)2 powders were prepared by NH3 coordination-precipitation method. The effects of SO42−, NO3−, Cl−, NH3, pH value on Ni(OH)2 structure and morphology were investigated experimentally, explained with the theoretical model that the growth units were the polyhedral structure of coordination anions. The results showed that the structure and morphology of Ni(OH)2 were effectively controlled by the growth units, the dimensions and the linking patterns of the growth units vary with the changes of physical and chemical conditions in the aqueous solution.
Topological method is applied firstly to calculate the group connectivity indexes of some flotation reagents for sulfide minerals and oxide minerals. The study reveals that some properties of flotation reagents, such as group electronegativity, energy criterion, solubility product of chemicals and maximum wavelength of ultraviolet absorbency, have linear correlation with the first order group connectivity index (GCI) of polar group, and the related coefficients are all larger than 0.900. The GCI can be used to characterize the structure of groups, and is a sort of new effective structural parameter to study the quantitative structure-activity relationship of flotation reagents.
In order to calculate the activity coefficients of water in aqueous solution of metal electrolytes, a simplified model predicting them in ternary or multicomponent solutions with common anions from the activity data of water of the corresponding binary systems has been developed based on an assumption that the electrolytes in the solution are treated as independent particles instead of their ion forms, and the interaction of the salt(i)-salt(j) pair in the solution is assumed to be much weaker than that of water-salt pair due to the common anions of both of salts. The model was applied to the systems such as KCl-H2O-NaCl, MCl-H2O-M′ Cl2 (M represents Na and K, M′ represents Ca and Ba) and KCl-H2O-NaCl-BaCl2 with satisfying results. The interchange energies of the studied component pairs between water and salts have also been determined by the corresponding binary aqueous solutions.
Kaolinite was hydrothermally synthesized from alumina gel and silicate by dissolving alumina gel in oxalic acid before it was mixed with silicate, effects of the amount of addition on the species of synthetic products were discussed. The reaction product was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The results show that analcite is the only phase of the reaction solution without oxalic acid, the proportion of kaolinite in product increases with the amount of addition, and kaolinite is the main species when the molar ratio of oxalic acid to alumina reaches 0.6:1.0. This is because oxalic acid addition is beneficial to the formation of kaolinite through changing the coordination number of aluminium from four to six, while the mixture of alumina gel, before it was dissolved in oxalic acid with silicate interfered with the crystallization of kaolinite.
Hydrothermal method was used to synthesize nanoscale particles of MnZn ferrites. The crystallites were characterized by XRD, TEM and SEM. The effects of the reaction time, temperature and additives on the product were investigated. Crystallization process would be carried out above 160 °C for 5 h or more, higher temperature can reduce the reaction time. Additives were used to remove impurities such as Fe2O3, ZnMnO3. 10–15 nm pure slightly agglomerated MnZn ferrite crystallites with a narrow grain size distribution were obtained.
The extraction separation of germanium from indium raffinate in hydrometallurgical zinc process was discussed. The conditions and mechanism of the extraction with hydroxamic acid HGS98 have been investigated in detail. The results show that using 2% (mass fraction) hydroxamic acid HGS98 and 5% D2EHPA as synergist, germanium is extracted (1-stage) over 99% in 5 min at phase ratio (Vo: Va) of 1:5 from indium raffinate with original acidity. Then, using 2 mol·L−1 NH4F as strip liquor, the stripping recovery is over 98% in 15 min at phase ratio of 1:1. This process has the following advantages: easy to operate, high recovery and selectivity, and lower investment cost. It provides a new way to recover rare metal — germanium from metallurgical spent residues.
Young’s Modulus of concrete is studied on the basis of triaxial compressive experiments. The authors proposed two empirical equations to calculate its static Young’s modulus and dynamic Young’s modulus when dynamic Poisson ratio μd varies nearby 0.20. P-wave velocity and elastic modulus have the same varying tendency as letter N. μ, μd decrease with the increase of loading rate and μd has a great effect on the parameters Ed and ED.
A hydraulic position system was designed employing two high speed On/Off solenoid valves with PWM(Pulse-width-modulation) technique and using LQ(Linear-Quadratic) optimization principle. Based on the system, the parts of system can be formulated with equations. According to equations, the mathematical model of the system was established. By simulation, the corresponding LQ optimal controller was designed and the PWM signals were generated. The comparison of the simulation and experiment results show that LQ optimal control method with PWM technique employing high speed On/Off solenoid valve can provide better system performance and a high position precision is obtained.
For a class of interconnected time-delay uncertain systems satisfing the matching conditions, the sufficient condition for decentralized stabilization feedback control laws is derived based on Lyapunov stability theorem. This condition is expressed as the solvability problem of linear matrix inequalities(LMI). It can be easily determined whether or not, it is feasible and one can easily obtain the decentralized stabilizing state feedback matrices via LMI techniques. The method overcomes the limitations of the existing algebraic Riccati equation method. The given example shows the application of the method.
Development of computational agent organizations or “societies” has become the domiant computing paradigm in the arena of Distributed Artificial Intelligence, and many foreseeable future applications need agent organizations, in which diversified agents cooperate in a distributed manner, forming teams. In such scenarios, the agents would need to know each other in order to facilitate the interactions. Moreover, agents in such an environment are not statically defined in advance but they can adaptively enter and leave an organization. This begs the question of how agents locate each other in order to cooperate in achieving organizational goals. Locating agents is a quite challenging task, especially in organizations that involve a large number of agents and where the resource avaiability is intermittent. The authors explore here an approach based on self-organization map (SOM) which will serve as a clustering method in the light of the knowledge gathered about various agents. The approach begins by categorizing agents using a selected set of agent properties. These categories are used to derive various ranks and a distance matrix. The SOM algorithm uses this matrix as input to obtain clusters of agents. These clusters reduce the search space, resulting in a relatively short agent search time.