The reduction of Fe3O4 to Fe is accomplished in two stages. In order to understand the reduction mechanism of magnetite cold bond pellets during the first period of heating-up process, it is necessary to study the kinetics of the reaction. In this work, the first stage of reduction of magnetite cold bond pellets, that is the reduction from Fe3O4 to FeO, has been investigated using an isothermal thermogravimetric method. Isothermal experiments were carried out at 750°C, 800°C, 850°C and 900°C, respectively. The results showed that the reaction was controlled by chemical reaction below 800°C, whereas, at higher temperature, it was controlled by a mixed controlled mechanism of chemical reaction and Ginstling-Brounshtein diffusion as well.
In the thermodynamics, for flotation separation of the Sb-As bulk concentrate system there is no potential extent using butyl xanthate as collector. However in the kinetics, there exists 150 mV in reducing potential of butyl dixanthogen on the surface of stibnite and arsenopyrite. In this paper, their reducing kinetic difference of electrochemistry was confirmed by pure mineral flotation under controlled potential, the artificial Sb-As bulk concentrate flotation separation and UV-spectrophotometic analysis. The electrochemical separation of Sb-As bulk concentrate has been carried out. qualified concentrate has been obtained. Sb-concentrate contains Sb 49.44 %, As 0.44 %, Sb-recovery is 87.83 % and As-concentrate contains As 10.96 %, As-recovery is 94.66 %.
Organic binder is used for briquetting manganese ore and coke fines to fabricate composite briquette with high strength and resistivity, thermal stability, good softening property and reducibility through simple process, which is advantageous to deep insertion of electrodes, improvement of permeability in burden layer and stabilization of operating process during smelting. Significant effects have been obtained from the industrial application in an 1800kVA ferromanganese arc furnace charged with 50 % of composite briquette: 20 % electricity was saved and 9.6 % more manganese was recovered.
The construction principle of the system for determination of xanthate concentration, which consists of an Ion-selective electrode (ISE) and a microprocessor based SDI analyzer, was described in the paper. The performances of the developed system were discussed in details. The results both detected in solutions and in sulfide mineral flotation system were given; also the results by ultraviolet spectrometry were compared with those by the developed system.
Effect of various aging treatments on the tensile properties and microstructure of 2195 alloy has been investigated. The experimental results show that promising combination of strength and ductility is achievable under T8 temper. The lower aging temperature reduces T1 precipitation on the subgrain or grain boundaries and favors uniform dispersion of T1 phases in the matrix, resulting in better strength and ductility. Prior deformation before aging has improved tensile strength with a slight decrease in ductility. Pre-aging after prior deformation had little effect on the age-hardening behavior of 2195 alloy.
The HfO2-CaO quasibinary system has been evaluated thermodynamically by means of Calphad technique. On the basis of extensive and careful evaluation of published experimental results, the optimization and calculation process has been carried out using Thermo-calc, a powerful, integrated package for thermochemical treatment. With the set of the optimized thermodynamic parameters the phase relationships have been predicted, the results were in good agreement with the experimental measurements. Two sets of phase combinations have been obtained corresponding to the disputes in experiments about the ordering phenomena in the low temperature range. It has been shown that more information is required on the liquidus and ordering behavior in this system.
The rapidly solidified powder of AlFeCrZrVSi aluminum alloy was prepared using multi-stage atomization and consolidated by hot-extrusion, the evolution of microstructure of the extruded materials during thermal exposure was studied with optical microscope, X-ray diffraction and transmission electron microscope (TEM). The results show that the majority of dispersions present in the as-extruded alloy are metastable Al12 (Fe, Cr, V)3Si, which has excellent thermal-dynamical stability and coarsening resistance; the coarsening rate-controlling process of the Al12 (Fe, Cr, V)3Si phase is considered to be diffusion of Fe atom along grain boundaries instead of bulk diffusion of Fe atom.
Sialon ceramic materials and its main three preparation methods have been outlined, among which preparing sialon powder from Kaolin through the carbothermal reduction and nitridation process is an economical, simple and practical synthesis process. However, the reaction system is complex due to the fact that there exist a lot of influencing factors and several reactions are taking place simutaneously. Partial reactions related to the chemical reaction system of the carbothermal and nitridation process, sialon powder prepared from the purified Kaolin, are analyzed thermodynamically, the systhesis temperature of sialon powder is 1400°C. The theoretical bases used to find the rational process of production are provided. The results prove to be practical.
Silica gel powders, with particle diameter in the range 10 to 20 nm, were prepared from water glass using ethyl acetate as a latent acid reagent. The products were characterized by TG-DTA, TEM, FTIR, BET and some other experiment methods. The process of silica sol-gel formation and the thermal behavior as well as phase change of the silica powders during heat-treating process were studied, and the effect of heat-treating temperature on the specific surface area and apparent density of the silica powders was investigated.
A series of oil products taken from oil refining factories were used as diluents for copper extraction. The influence of diluents on extraction properties has been investigated. The extractants used are Lix984(Henkel) and M5640(Zeneca), and the adaptability of this diluents to these extractants is compared. The checked extraction properties include loading capacity, extraction and strip kinetics, copper/iron selectivity and phase disengagement. The results showed that DSR3 is a suitable diluent for M5640 and Lix984. Further research has been done to reduce the cost of this product by omitting several steps from its production process.
Based on thermo-electrochemical equation for an electrode reaction, the entropy change of it can be obtained by the thermo - electrochemical technology (TECT). The entropy changes of Fe (CN)6−3/Fe (CN)6−4, H+/H2(P0), Cu+2/Cu and Zn+2/Zn electrode reaction systems and the dilute enthalpies of the H+, Cu2+ and Zn2+ ions under the ion concentrations studied have been determined by a specially designed thermo-electrochemical equipment. The enthalpy change and entropy change for the five systems at unlimitedly diluted concentrations agree well with the literature.
The solution-fluorescence quenching mechanisms of poly (methylcyclohexylsilane), poly (methylphenethylsilane), poly (methylcyclohexylsilane-co-methylphenethylsilane) and poly (methylphenylsilane) are studied by means of steady-state fluorescence, time-resolved fluorescence and UV absorption. The results show that the fluorescence quenching for polysilanes by carbon tetrachloride is the static quenching with energy migration, which is also supported by the qualitative results of the fluorescence quenching behaviors of polysilane by nitromethane (CH3NO2) and 2, 4, 7-trinitrofluorenone (TNF).
The chelates of metal ions with EDTA covalently linked to the 5′-end of oligodeoxyribonuclotides (ODN), i. e,ODN-5′-EDTA·M(II), are prepared, in which M(II) is Fe(II), Co(II) or Cu(II). The optimum pH value for forming these three chelates is calculated. For ODN-5′-EDTA Fe(II) pH value is 5.8 to 8.6, pH 4.6–8.1 for ODN-5′-EDTA Co(II), and pH 3.4–5.7 for ODN-5′-EDTA Cu(II). Under such pH value conditions neither can Mg(II) ion, necessary for cleavage reaction, be competitive with Fe(II), Co(II) or Cu(II) to form EDTA chelate, nor can it be precipitated. The cleavage mechanism of OND-5′-EDTA Fe(II) for DNA duplex is discussed. Modified ODN binds with DNA duplex in the major groove via hydrogen bond to form triple helix. In the presense of oxygen and reducing agent dithiothreitol, hydroxyl radicals species are generated as intermediates by catalysis of metal ions, and then oxidize the ribo ring and cut the double-stranded DNA at the sites close to the EDTA·Fe(II).
Complex coupling problems have been existing in electromechanical systems. According to the principles of fractal geometry, an electromechanical system was to be resolved into some simple subsystems that can be easily described and solved. Pattern recognition theory was applied to recognize the most probable solution space. Multiple-target decision method was used to synthesize the fractal solutions of a system. A kind of fractal-concurrentsynthetic design strategy, and some decoupling optimum techniques were suggested in the article.
The fatigue life for components can be predicted by the plot method which is easy and convenient in engineering. Based on the usual fatigue life prediction formula, a new formula for estimating the low stress and high cycle fatigue life is proposed and deduced, which has adopted more accurate S-N curve relationship — Weibull S-N curve formula. The solution of the new formula is given, too. In addition, an example has been calculated and proved in practice. The results of the new formula and the old one are given and compared.
Since loading wave shapes are very important in the study of rock dynamical properties, a new procedure for obtaining a variety of wave shapes using equi-diameter impact hammer of conventional SHPB device is proposed based on theoretical analysis. Experiment shows that different loading wave shapes can be obtained through varying the radius at impact end of hammer. Experiment results are quite consistent with the theoretical analysis.
Some typical structural schemes of learning control have been investigated. The schemes involve the pattern recognition-based learning control, iterative learning control, repetitive learning control, and connectionist learning control, etc. This study focuses on the control mechanism and provides a basis for potential applications. Most of the structural schemes have been applied to various control fields.
Focussing on unification of concrete portions into a generic form of computational evolution, a generalized theoretical framework is necessary and imperative to be built to construct a universal computational theory of evolution machine. The NP problem solving capacity can be traced to the nature of meta-evolution mechanism with emergence features that determine corresponding homeostasis and diversity ranging in the domain of nonlinnear mapping from genotype to phenotype. In this paper a criterion that guarantees the global optimality of evolutionary computation process is proposed and proven rigorously. The global optimization criterion obtained is based on the non-parametric measarement for the whole evolution system and has great flexibility and evolvability. It leaves room for evolutionary system designing and developement. The formulization of the global description in statistical manifold space of information object family expresses evoluable evolutionary operator architecture and operation procedure in terms of evolution by evolution. The theoretical results are helpful to applications such as machine learning for automatic knowledge acquisition, pattern classification and recognition of complex images (e. q. OCR) and unsupervised system identification of nonlinear dynamical systems as well as chaos phenomena. The kernal of the formal system guided by global evolutionary optimization is proper to the implementation with object-oriented programming paradigm and abstract machine modelling.
A μ analysis and μ synthesis method for nonlinear robust control systems was presented. The nonlinear robust control problem using μ method was described. By means of the nonlinear state feedback and state coordinates transformation, many uncertain nonlinear systems can be transformed as a linear fractional transformation (LFT) on the generalized plant and the uncertainty. Based on the LFT, a linear robust controller can be obtained by the D-K iteration and then a corresponding nonlinear robust control law is constructed. An example was given in the paper.