Anodic polarization behavior of gold, silver, copper, nickel and iron in potentiostatic condition has been examined in an alkaline aqueous thiourea solution, where gold is hardly dissoluble normally. The addition of Na₂SO₃ into the solution can accelerate anodic dissolution of gold. The factors affecting selective dissolution of gold in the alkaline thiourea solution by electrolysis have been studied, and the optimum condition was obtained. In 0.1 mol/L thiourea solution of pH 12.5 containing 0.5 mol/L Na₂SO₃ and 2.5% acetone, at the potential of 0.34 V vs NHE, at the temperature of 323 K, the dissolved mass of gold anode with the exposed area of 1.0 cm² reached more than 300 mg · dm⁻³ within 30 min, and other metals such as silver, copper, nickel and iron could hardly dissolve.

Gold dissolves easily in an alkaline thiourea solution with Na₂SO₃ and Na₂S₂O₈, where the accompanied elements of Au, such as Ag, Cu, Ni and Fe can hardly dissolve. It was considered that electrochemical reduction and catalytic action of SO₃²⁻ prevent thiourea from decomposing irreversibly and accelerates dissolution of gold. The S₂O₈²⁻ as an oxidant can control the potential so that formamidine disulfide may form efficiently. The dissolution of gold is mainly through oxidation of Au by formamidine disulfide and compexation of thiourea with Au⁺, and not direct oxidation of S₂O₈²⁻. Thus, sufficient formamidine disulfide is necessary to accelerate the dissolution of gold. The reason for Ag, Cu hardly being dissoluble is that the black layers of Ag₂S and Cu_1.92S form on the surface of Ag and Cu. The metal Ni and Fe do not dissolve in the alkaline media due to their sulfide films passivation samely.

A computer model has been developed to simulate the nickel smelting process. The primary assumption of the model is that six phases in the nickel smelting furnace are in chemical equilibrium. The amounts of all components in matte, slag and gaseous phases under equilibrium are calculated by using the data of free energies of formation and activity coefficients of components. Two nickel sulfide species are used to allow for the modeling of sulfur-deficient mattes. The predictions by the present computer model are compared with the known data from Kalgoorlie nickel flash smelting. The agreements between the computer predictions and the known data are excellent, so that the present computer model can be used to monitor and optimize the actual industrial operations of nickel smelting process. The distribution behaviors of Ni, Co, Cu, Fe, S and O in the nickel smelting furnace are basically dependent on the process factors such as smelting temperature, volumes of air, and the element content.

The regularities of anodic oxidation of thiosulfate ions on a gold electrode have been investigated using electrochemical methods in order to improve gold extraction. Effects of ammon, copper-ammon ions, pH and sulphite on anodic oxidation of thiosulfate ions have been examined in details. Results show that the anodic oxidation of thiosulfate ions is an inreversible reaction whose oxidizing peak potential is 620 mV/SCE in the absence of ammon. Oxidation rate increases with concentration of thiosulfate ions, but not in linear relation. It is also shown that ammon has significant effects on the oxidation of thiosulfate ions by causing great decrease in oxidation rate and negative shift of peak potential. The degrees of the rate decrease and negative shift increase with ammon concentration. When ammon concentration is incrcased to 1. 0 mol/L, the oxidation rate decreases to one fourth of that without ammon and the peak potential shifts from 620 mV/SCE to 350 mV/SCE.

A new technology of one-step leaching of refractory gold concentrate containing arsenic and sulfur was studied and 96.8% of gold was extracted in an hour by this technology. Themodynamic possibility of reactions of arsenopyrite, pyrite and gold with sodium hypochlorite in NaOH medium, and solution chemistry of H₃AuO₃ at different pH values were analyzed. The reason why the gold wrapped by FeAsS, FeS₂ can be leached out rapidly by grnding of porcelain ball mill, is explained.

A new secondary ore of rare earth was discovered in the Southwest of China. It is a kind of product of the weathered mineral. The rare earth elements (REE) in it exist probably as ionic characteristic adsorption state in manganesian and ferric oxide colloid mineral, and one bearer of REE is amorphous ferric oxide gel. It is necessary to study the binding state of rare earth elements on manganesian and ferric oxide in order to utilize comprehensively the rare earth resources and avoid latent influence on the environment resulting from the fact that high-content rare earth elements are carried into soil by the mineral efflorescence. A simulating adsorption test of rare earth ions in weak acid media is carried out with ferric oxide gel prepared by sol-gel method. The experimental results show that the characteristics of adsorption isotherm correspond well with the Flory-Huggins equation, but deviated from the Langmuir equation. The standard molar adsorption Gibbs function, standard molar adsorption entropy and standard molar adsorption enthaply are calculated. The measurements of the point of zero charge and isoelectric point show occurrence of the characteristic adsorption. It has been proved that the OH group on the skeleton of ferric oxide gel is the innate cause of the characteristic adsorption.

A mixed method which combines the recent developed finite analytical method and the boundary fitting coordinate transformation method was used first to calculate the temperature field and thermal stress field of the cold roller in this paper. The following results are obtained by the calculation:thermal stresses σ_r=0, σ_θ=σ_z are maximum tension stress on the inner surface of the cold roller and σ_r=0, |σ_θ|=|σ_z| are maximum compression stress on the outer surface of the cold roller in the steady and unsteady case. Effectiveness and validity of the mixed method are checked with steady coll roller problems having theoretical solutions. The results show that good agreement is achived between the calculated value and theoretical solution, and the mixed method used in the paper is very workable. The mixed method is also useful in solving the steady and unsteady thermal stress field proplems of the hot -rolled for the reversing rolling mill and the continous rolling mill.

DC Resistivity Tomography is a non-linear inversion problem. So far there are mainly two kinds of inversion methods, based on the finite-element method and alpha centers method. In this paper, the disadvantages of these two kinds of methods were analysed, and a new method of forward modeling and inversion (Tomography) based on boundary integral equations was proposed. This scheme successfuly overcomes the difficulties of the two formarly methods. It isn’t necessary to use the linearization approximation and calculate the Jacobi matrix. Numerical modeling results given in this paper showed that the computation speed of our method is fast, and there is not any special requirement for initial model, and satisfying results of tomography can be obtained in the case of great contrast of conductivity. So it has wide applications.

The ZrO₂-AlO_1.5 quasibinary system has been assessed by means of the CALPHAD (CALculation of PHAse Diagram) technique. The liquid phase, cubic (fluorite-type) zirconia solid solution and tetragonal zirconia solid solution are described by a regular solution model. The monoclinic zirconia and α-AlO_1.5 are treated as stoichiometric phase. A consistent set of optimized parameters describing the system have been obtained to agree with almost all of the avaiable experimental data. Comparisons between the assessed and experimental data are presented. It is shown that further studies are needed for equilibrium solubilities of AlO_1.5 in ZrO₂ phases.

The degradation phenomena due to the energy pulse in the high-energy ZnO varistors used for de-exitation and overvoltage protection of hydroelectric generator are investigated. The energy pulse, obtained by releasing the energy stored in an inductor, can be equivalent to the combination of the DC field components and the energy component. The variations of the characterized voltages, nonlinear coefficients and pre-breakdown V-A characteristics, increase with the number of the applied energy pulse. The asymmetrical variations of the electric properties of the high-energy ZnO varistors after the energy pulse arise from the deformation of the double Schottky barriers due to the ion migration occuring in the depletion layer and in the grain boundary.

The principles for measuring characteristic grain sizes of materials, such as fully-dense single phase materials, porous materials and materials with isolated second phase particles, are developed on the basis of its definition associated closely with the surface area per unit volume, Sv, of grain. The focus of the measuring principles of the characteristic grain size is put on determining Sv of grains. Unlike the measurement of average grain size commonly used, G, correcting factors such as grain shape and grain size distribution factors, will not be applied to the determination of the characteristic grain size, G_c, due to its unique geometric meaning and the measure precision of S_v being guaranteed by quantitative stereological technique and gas adsorption method. The measurement of G_c can be directly carried out on the polished and etched cross section of materials, similar to the measurement of the average grain size using the Heyn intercept method.

The fracture behavior of Al-8. 5Fe-1. 3V-1. 7Si (mass fraction,%) alloy under different deforming conditions was investigated. The results show that the propagation mode of the main crack was correlated with the orientation of prior powder boundaries (PPB’s) when the specimen ruptured. For the L-direction tensile specimen, the LT-oriented microcrack along PPB’s didn’t affect the main crack’s extension; the LS-oriented microcrack might lead to unusual failure; the TS-oriented boundary was ready to become the low-energy propagating path for the main crack. Hot rolling resulted in a larger increase of the cohesion strength of LS-and TS-oriented boundaries than that of LT-oriented boundary, thus causing the corresponding change of fracture mode at a certain deformation amount (30%). The different variation tendency for fracture strength and elongation arised from this change of fracture mode and subsequent work hardening.

An analytical model based on the rigid-plastic finite-element formulation for slightly compressible materials is newly proposed to examine the bonding behavior at the roll gap during clad metal sheets rolling. The interfacial elements inserted between the two metals, which are characteristic of the shear-susceptible deformation with the help of the shear factor in the expression of effective strain rate, are used to model the relative slidding at the interface. It is found that the proposed method is applicable to the simulation of clad metal sheets rolling.

A dynamic genetic algorithms based on numeric encoding is proposed and its application in system identification is discussed. Simulation shows that the introduction of both numeric encoding and dynamic mutation can effectively improve the accuracy and speed of searching for the optimum. It also show that the improved Genetic algorithm can identify time delay and parameters of the plant at the same time and converge to globle optimization.

Some typical structural schemes of Fuzzy control have been surveyed. Besides general structure of fuzzy logic controller (FLC), the structural schemes include PID fuzzy controller, self-organizing fuzzy controller, selftuning fuzzy controller, self-learning fuzzy controller, and expect fuzzy controller, etc. This survey focuses on the control principle, and provides a basis for potential applications. Most of the structures have been used in various control fields, one of application areas is in the metallurgy industry, e.g., the temperature control of the electric furnace, the control of the aluminum smelting process, etc. According to the application requirements, one can choose a structural scheme for special use.

Previous studies have confirmed that an active suspension system with high speed ON/OFF solenoid valves could provide the same vibration isolation efficiency as that of system with pressure proportional valve. In this study, by using Linear—quadratic optimization technique and Kalman filter method, an optimal regulator controller with a state observer was designed for the proposed system. Simulation and experimental research was conducted on a quarter car model. The simulation analysis of the system frequency characteristic suggested that the peak value of magnitude response curve in the case of system with an optimal controller would be lowered significantly, and the experiment results also showed that an improvement in the vibration isolation effect was obtained in using the designed optimal controller over the sky hook damper controller.

The calibration curves obtained using strain gages are used to predict surface crack length on plate specimen subjected to 4-point bending fatigue loading. The results shows that the proposed procedure is of high precision with the maximum error percentage being less than 6%,and it can be easily used to estimate or monitor the surface crack length under fatigue loading both in laboratory and in engineering. It is also quite meanful for nondamage detecting.