Search1999 Vol. 6, No. 2
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1999, vol. 6, no. 2, pp.
77-82.
Abstract:
Located in the mid-west of Inner Mongolia, Daqingshan district has many gold deposits occurring along a east-west striking ductile shear zone within a greenstone belt, which is mainly composed of the Archean Wulashan group. The hydrothermal mineralization can be divided into four stages: (1) pyrite-quartz, (2) quartz-pyrite, (3) polymetallic sulfides and (4) carbonates-quartz. The major metallic minerals in the ore of gold-bearing veins are native gold, electrum, pyrite, chalcopyrite and galena, but the gangue minerals are mainly quartz, secondarily sericite, ankerite and calcite. Principal alteration patterns in the gold deposits are sericitization, silicification, pyritization, carbonatization and chloritization. An investigation on fluid inclusions shows that the ore-forming fluids were low in salinities and high in CO2 content. Measured δD of fluid inclusions in quartz from the ore veins ranges from -65 ‰ to -104 ‰, but δ18Oquartz from 10.0‰ to 12.8‰. These data show that the water in hydrothermal fluid precipitating the ore bodies could have been mainly magmatic water and metamorphic water, but local meteoric water might take part in the late mineralization. δ13C from fluid inclusions in the ore varys from -3.3‰ to -6.2‰, indicating that carbon was derived from magmatic or anatectic source. δ34s from sulfide samples in gold deposits ranges from -4.1‰ to +4.0 ‰, which are identical with that from Shi, et al. It is concluded that the gold deposits in Daqingshan district are similar to those in Xiaoqinling area, in aspects of geological characteristics, mineral association and stable isotope composition.
Located in the mid-west of Inner Mongolia, Daqingshan district has many gold deposits occurring along a east-west striking ductile shear zone within a greenstone belt, which is mainly composed of the Archean Wulashan group. The hydrothermal mineralization can be divided into four stages: (1) pyrite-quartz, (2) quartz-pyrite, (3) polymetallic sulfides and (4) carbonates-quartz. The major metallic minerals in the ore of gold-bearing veins are native gold, electrum, pyrite, chalcopyrite and galena, but the gangue minerals are mainly quartz, secondarily sericite, ankerite and calcite. Principal alteration patterns in the gold deposits are sericitization, silicification, pyritization, carbonatization and chloritization. An investigation on fluid inclusions shows that the ore-forming fluids were low in salinities and high in CO2 content. Measured δD of fluid inclusions in quartz from the ore veins ranges from -65 ‰ to -104 ‰, but δ18Oquartz from 10.0‰ to 12.8‰. These data show that the water in hydrothermal fluid precipitating the ore bodies could have been mainly magmatic water and metamorphic water, but local meteoric water might take part in the late mineralization. δ13C from fluid inclusions in the ore varys from -3.3‰ to -6.2‰, indicating that carbon was derived from magmatic or anatectic source. δ34s from sulfide samples in gold deposits ranges from -4.1‰ to +4.0 ‰, which are identical with that from Shi, et al. It is concluded that the gold deposits in Daqingshan district are similar to those in Xiaoqinling area, in aspects of geological characteristics, mineral association and stable isotope composition.
1999, vol. 6, no. 2, pp.
83-89.
Abstract:
To investigate the mechanism and influence of oxide and niobium metal on the electrodeposition of niobium, the electrochemical reaction mechanisms of niobium ions in LiF-NaF-KF eutectic (FLINAK) melt at 973 K was studied by chronopotentiometry, chronoamperometry and cyclic voltammetry. The electrochemical reduction process of Nb(V) (K2NbF7) in FLINAK melt relates to the complex anions. A two-step electrochemical reduction with disproportionate and catalytic reactions is proposed. The metallic niobium in K2NbF7-FLINAK melt can reduce the catalytic reaction. The influence of oxide (Na2O) on the electrochemical processes of Nb(V) in K2NbF7-FLINAK-O2- melts without and with niobium metal present was also studied. When oxide present in K2NbF7-FLINAK melt, a much stable oxyfluorocomplex ion is formed. Cyclic voltammetry showed that the reduction potential of oxyfluoro-complex ion is more negative than that of fluorocomplex ion (NbF62-). The electrochemical stability of NbOF63- is higher than those of NbF72- and NbF62-. An optimum composition for a coherent niobium metal coating on low-carbon steel is found to be 2.7%K2NbF7-0.5～2.0%Na2O-FLINAK in molar fraction. The cathodic current density is about 90 mA/cm2.
To investigate the mechanism and influence of oxide and niobium metal on the electrodeposition of niobium, the electrochemical reaction mechanisms of niobium ions in LiF-NaF-KF eutectic (FLINAK) melt at 973 K was studied by chronopotentiometry, chronoamperometry and cyclic voltammetry. The electrochemical reduction process of Nb(V) (K2NbF7) in FLINAK melt relates to the complex anions. A two-step electrochemical reduction with disproportionate and catalytic reactions is proposed. The metallic niobium in K2NbF7-FLINAK melt can reduce the catalytic reaction. The influence of oxide (Na2O) on the electrochemical processes of Nb(V) in K2NbF7-FLINAK-O2- melts without and with niobium metal present was also studied. When oxide present in K2NbF7-FLINAK melt, a much stable oxyfluorocomplex ion is formed. Cyclic voltammetry showed that the reduction potential of oxyfluoro-complex ion is more negative than that of fluorocomplex ion (NbF62-). The electrochemical stability of NbOF63- is higher than those of NbF72- and NbF62-. An optimum composition for a coherent niobium metal coating on low-carbon steel is found to be 2.7%K2NbF7-0.5～2.0%Na2O-FLINAK in molar fraction. The cathodic current density is about 90 mA/cm2.
1999, vol. 6, no. 2, pp.
90-93.
Abstract:
Fluidized beds are nonlinear dynamic systems that exchange mass and energy with outside. They are governed not only by fluid dynamics, but by thermodynamics, especially the second law of thermodynamics as well. According to Prigogine's dissipative structure theory, the following have been concluded: (1) a fixed bed is on thermodynamic blanch, and bubbling, turbulent and fast beds are on the dissipatve structure branches. (2) Entropy in fluidized beds is divided into two parts: entropy production and entropy flux. The latter increases with gas velocity and decreases with pressure of the systems. That means the entropy of a system may reduce and the system with higher gas velocity behaves as dissipative structure characteristics. (3) For a given velocity, a fluidized bed operates stably on the whole, but it is unstable to local gas-solid phases. The unstable phases are described by fluid dynamic equations, While the minimum of system energy function assures whole stability of the system. (4) A transition criterion of a bubbling bed is derived from Prigogine's stability theory.
Fluidized beds are nonlinear dynamic systems that exchange mass and energy with outside. They are governed not only by fluid dynamics, but by thermodynamics, especially the second law of thermodynamics as well. According to Prigogine's dissipative structure theory, the following have been concluded: (1) a fixed bed is on thermodynamic blanch, and bubbling, turbulent and fast beds are on the dissipatve structure branches. (2) Entropy in fluidized beds is divided into two parts: entropy production and entropy flux. The latter increases with gas velocity and decreases with pressure of the systems. That means the entropy of a system may reduce and the system with higher gas velocity behaves as dissipative structure characteristics. (3) For a given velocity, a fluidized bed operates stably on the whole, but it is unstable to local gas-solid phases. The unstable phases are described by fluid dynamic equations, While the minimum of system energy function assures whole stability of the system. (4) A transition criterion of a bubbling bed is derived from Prigogine's stability theory.
1999, vol. 6, no. 2, pp.
94-96.
Abstract:
Pulse Electric Discharging (PED) is a novel technique that can modify solidifying structure and reduce grain size. Its effects applied to the high carbon liquid steel were presented here. The macrostructure and microstructure of the high carbon alloy steel were also observed. Results show that (1 ) the length of columnar crystal at the edge of ingot without PED treatment is much longer than that with PED, and (2) the perlite lamellae of steel billets after deposed by PED are twisted and shortened. An explanation of those experimental results is given.
Pulse Electric Discharging (PED) is a novel technique that can modify solidifying structure and reduce grain size. Its effects applied to the high carbon liquid steel were presented here. The macrostructure and microstructure of the high carbon alloy steel were also observed. Results show that (1 ) the length of columnar crystal at the edge of ingot without PED treatment is much longer than that with PED, and (2) the perlite lamellae of steel billets after deposed by PED are twisted and shortened. An explanation of those experimental results is given.
1999, vol. 6, no. 2, pp.
97-102.
Abstract:
When making a diamond film by direct current plasma jet, a kind piece of flake is used as a base body Which the film can be attached to. The flake's temperature is unstable. Therefore, some experiments and constructed mathematical models, which were solved by computer, were done. The results show that the flake's temperature is influenced by many factors and the mains are plasma jet power and vacuum pressure. Through adjusting the two parameters, the flake's temperature can be accurately controlled, furthermore, diamond films' quality would be improved. Lowering sediment platform's temperature has a little effect to the flake's temperature at present technology conditions.
When making a diamond film by direct current plasma jet, a kind piece of flake is used as a base body Which the film can be attached to. The flake's temperature is unstable. Therefore, some experiments and constructed mathematical models, which were solved by computer, were done. The results show that the flake's temperature is influenced by many factors and the mains are plasma jet power and vacuum pressure. Through adjusting the two parameters, the flake's temperature can be accurately controlled, furthermore, diamond films' quality would be improved. Lowering sediment platform's temperature has a little effect to the flake's temperature at present technology conditions.
1999, vol. 6, no. 2, pp.
103-106.
Abstract:
Based on the microstructures of steel, a thermo-elasto-plastic stress model of continuously casting billets is established to study hailal solidifying process in molds. Results show that peritectic phase transformation contributes greatly to the irregular shrinkage of initial shell, which makes the billets vulnerable to surface defects.
Based on the microstructures of steel, a thermo-elasto-plastic stress model of continuously casting billets is established to study hailal solidifying process in molds. Results show that peritectic phase transformation contributes greatly to the irregular shrinkage of initial shell, which makes the billets vulnerable to surface defects.
1999, vol. 6, no. 2, pp.
107-110.
Abstract:
A prediction model for Current Efficiency (CE) of low temperature aluminum electrolysis (LTAE) with the low molar ratio electrolyte of Na3AIF6-AIF3-CaF2-MgF2-LiF-Al2O3 system was investigated based on artificial neural network principles. The nonlinear mapping between CE of LATE and various electrolytic conditions was obtained from a number of experimental data and used to predictCE of LATE. The trained neural networks possessed high precision and resulted in a good predicting effect. As a result, artificial neural networks as a new cooperating and predicting technology provide a new approach to the further studies on low temperature aluminum electrolysis.
A prediction model for Current Efficiency (CE) of low temperature aluminum electrolysis (LTAE) with the low molar ratio electrolyte of Na3AIF6-AIF3-CaF2-MgF2-LiF-Al2O3 system was investigated based on artificial neural network principles. The nonlinear mapping between CE of LATE and various electrolytic conditions was obtained from a number of experimental data and used to predictCE of LATE. The trained neural networks possessed high precision and resulted in a good predicting effect. As a result, artificial neural networks as a new cooperating and predicting technology provide a new approach to the further studies on low temperature aluminum electrolysis.
1999, vol. 6, no. 2, pp.
111-115.
Abstract:
Fe-Cr-Mn (W, V) austenite steel was researched in order to supply a theory base for the first wall materials of fusion reactors.Experiments included vacuum melting, forging, annealing, solution treatment, Charpy impact tests and microstructure observation. The results show that the imped value decreases with the test temperature decreasing. In this system, there is ductile/brittle transition. The mechanism of this decrease of the impact value is considered to be due to γ→ε transformation in sub-stable austenite steel and stopping overlapping sacking fault by grain boundaries in stable austenite steel.
Fe-Cr-Mn (W, V) austenite steel was researched in order to supply a theory base for the first wall materials of fusion reactors.Experiments included vacuum melting, forging, annealing, solution treatment, Charpy impact tests and microstructure observation. The results show that the imped value decreases with the test temperature decreasing. In this system, there is ductile/brittle transition. The mechanism of this decrease of the impact value is considered to be due to γ→ε transformation in sub-stable austenite steel and stopping overlapping sacking fault by grain boundaries in stable austenite steel.
1999, vol. 6, no. 2, pp.
116-118.
Abstract:
Fully dense MoSi2-SiC composites were fabricated from the mixed powder of the elemental constituents by a spark plasma sintering method. The sintering and densification of the Mo-Si-C mixed powder are accomplished through three processes. In particular, it proceeds rapidly by the formation of MoSi2. The most suitable temperature for the fabrication of MoSi2-SiC composites depends on the content of SiC and increases with the content of SiC increasing. As a result, fully dense MoSi2-SiC composites can be prepared without difficulty by a spark plasma sintering method.
Fully dense MoSi2-SiC composites were fabricated from the mixed powder of the elemental constituents by a spark plasma sintering method. The sintering and densification of the Mo-Si-C mixed powder are accomplished through three processes. In particular, it proceeds rapidly by the formation of MoSi2. The most suitable temperature for the fabrication of MoSi2-SiC composites depends on the content of SiC and increases with the content of SiC increasing. As a result, fully dense MoSi2-SiC composites can be prepared without difficulty by a spark plasma sintering method.
1999, vol. 6, no. 2, pp.
119-124.
Abstract:
The microstructure change in thin NiFe/Cu/NiFe films during the magnetization process was observed by the Lorentz electron microscopy. Two types of films were prepared: (1) one NiFe layer with anisotropy and the other layer without, and (2) both NiFe layers have anisotropy normal each other. The domain wall migration and magnetization rotation processes in each of NiFe layers could be observed separately. The presence of magnetic anisotropy in the magnetic layer effectively controls the behavior of magnetic domains. The interaction between the two NiFe layers of the film could be observed not so strong in the present experiment.
The microstructure change in thin NiFe/Cu/NiFe films during the magnetization process was observed by the Lorentz electron microscopy. Two types of films were prepared: (1) one NiFe layer with anisotropy and the other layer without, and (2) both NiFe layers have anisotropy normal each other. The domain wall migration and magnetization rotation processes in each of NiFe layers could be observed separately. The presence of magnetic anisotropy in the magnetic layer effectively controls the behavior of magnetic domains. The interaction between the two NiFe layers of the film could be observed not so strong in the present experiment.
1999, vol. 6, no. 2, pp.
125-128.
Abstract:
Environmental effects, especially O2 pressure, often make SiC/SiC composites degraded. In order to investigate the effects on microstructural stability, SiC/SiC composite specimens, made of Hi-NicalonTM SiC fibers, were annealed under a commercial grade Ar flow and an ultra-high purified Ar flow respectively. The microstructural evolution in SiC/SiC composites was examined by a field emission type high-resolution electron microscopy and a parallel electron energy loss spectroscopy. A possible mechanism for this degradation was discussed.
Environmental effects, especially O2 pressure, often make SiC/SiC composites degraded. In order to investigate the effects on microstructural stability, SiC/SiC composite specimens, made of Hi-NicalonTM SiC fibers, were annealed under a commercial grade Ar flow and an ultra-high purified Ar flow respectively. The microstructural evolution in SiC/SiC composites was examined by a field emission type high-resolution electron microscopy and a parallel electron energy loss spectroscopy. A possible mechanism for this degradation was discussed.
1999, vol. 6, no. 2, pp.
129-132.
Abstract:
An unusual form of localized corrsion in copper tubes was detected early in service and in leakage tests after manufacturing.The morphology of this corrosion is similar to that of an ant's nest when viewed in cross section. The corrosion mechanisms, cases of ant's nest corrosion, and preventive measures are presented.
An unusual form of localized corrsion in copper tubes was detected early in service and in leakage tests after manufacturing.The morphology of this corrosion is similar to that of an ant's nest when viewed in cross section. The corrosion mechanisms, cases of ant's nest corrosion, and preventive measures are presented.
1999, vol. 6, no. 2, pp.
133-135.
Abstract:
Three kinds of high-purity Al2O3 powders, whose average particle size is 0.1, 0.3 and 3.0 mμ respectively, were used as the starting power, and their compacts were fired in the radio-frequency plasma generated at a pressure of 80 Pa using N, as the working gas.Experimental results show that the 0. 1 and 0.3 mp powder compacts can be sintered to nearly the theoretical density within 60 s and this sintering is almost finished in the heating period. It is concluded that the mechanism of liquid sintering, the electric charge effect of Al2O3 powder, and the effect of tempetrature gradient in the compacts can affect simultaneously on the rapid densification of the compacts in the plasma sintering.
Three kinds of high-purity Al2O3 powders, whose average particle size is 0.1, 0.3 and 3.0 mμ respectively, were used as the starting power, and their compacts were fired in the radio-frequency plasma generated at a pressure of 80 Pa using N, as the working gas.Experimental results show that the 0. 1 and 0.3 mp powder compacts can be sintered to nearly the theoretical density within 60 s and this sintering is almost finished in the heating period. It is concluded that the mechanism of liquid sintering, the electric charge effect of Al2O3 powder, and the effect of tempetrature gradient in the compacts can affect simultaneously on the rapid densification of the compacts in the plasma sintering.
1999, vol. 6, no. 2, pp.
136-138.
Abstract:
Scanning Probe Microscope (SPM) has great advantages in quantitative micromorphology analysis because of its convenience in obtaining micromorphology information of materials on nanometer or atomic scale under control of a computer. Based on an established SPM quantitative micromorphology analysis model, an SPM image analysis software Which can calculate both two- and three-dimensional micromorphology parameters is developed.
Scanning Probe Microscope (SPM) has great advantages in quantitative micromorphology analysis because of its convenience in obtaining micromorphology information of materials on nanometer or atomic scale under control of a computer. Based on an established SPM quantitative micromorphology analysis model, an SPM image analysis software Which can calculate both two- and three-dimensional micromorphology parameters is developed.
1999, vol. 6, no. 2, pp.
139-143.
Abstract:
The ordered event model is improved to describe serial production lines with limited buffer sizes. The improved model has the same computational burden as the original one and can be constructed directly according to given principles. Several simulation examples are cited to verify this improved model. Extensions and open problems are also indicated. By means of this new model, serial produotion lines with limitations of resources can be studied analytically.
The ordered event model is improved to describe serial production lines with limited buffer sizes. The improved model has the same computational burden as the original one and can be constructed directly according to given principles. Several simulation examples are cited to verify this improved model. Extensions and open problems are also indicated. By means of this new model, serial produotion lines with limitations of resources can be studied analytically.
1999, vol. 6, no. 2, pp.
144-148.
Abstract:
In order to improve the robustness and noise resistance of generalized minimum valance control systems, several generalized minimum variance control schemes are synthetically analyzed. The output variance caused by stochastic noise is decomposed to two parts. One part accords with the output variance of minboum vedance control and the other is the additional term of output variance caused by the control weighting factors. At the same time, the sensitivity function of modeling error is also deduced. A new robust design method that can minimize the sensitivity and the additional part of output variance is Presented by regulating variable parameters of contollers. The simulation results of self-tuning control show the effect of this method.
In order to improve the robustness and noise resistance of generalized minimum valance control systems, several generalized minimum variance control schemes are synthetically analyzed. The output variance caused by stochastic noise is decomposed to two parts. One part accords with the output variance of minboum vedance control and the other is the additional term of output variance caused by the control weighting factors. At the same time, the sensitivity function of modeling error is also deduced. A new robust design method that can minimize the sensitivity and the additional part of output variance is Presented by regulating variable parameters of contollers. The simulation results of self-tuning control show the effect of this method.
1999, vol. 6, no. 2, pp.
149-151.
Abstract:
In order to apply a new dynamic neural network-Diagonal Recurrent Neural NetWork (DRNN) to the system identification of nonlinear dynamic Systems and construct more accurate system models, the structure and learning method (DBP algorithm) of the DRNN are Presented. Nonlinear system characteristics can be identified by presenting a set of input / output patterns to the DRNN and adjusting its weights with the DBP algorithm. Experimental results show that the DRNN has good performances in the identification of nonlinear dynamic systems in comparison with BP networks.
In order to apply a new dynamic neural network-Diagonal Recurrent Neural NetWork (DRNN) to the system identification of nonlinear dynamic Systems and construct more accurate system models, the structure and learning method (DBP algorithm) of the DRNN are Presented. Nonlinear system characteristics can be identified by presenting a set of input / output patterns to the DRNN and adjusting its weights with the DBP algorithm. Experimental results show that the DRNN has good performances in the identification of nonlinear dynamic systems in comparison with BP networks.
1999, vol. 6, no. 2, pp.
152-153.
Abstract:
A type of single neuron adaptive PID regulator with auto-tuning gain is proposed and applied to the work control of fans, water pumps and air-pressers etc. in Handan Iron & Steel Compel China. The robustness of industrial parameter closed-loop process control systems is improved, and the work quality of the systems bettered.
A type of single neuron adaptive PID regulator with auto-tuning gain is proposed and applied to the work control of fans, water pumps and air-pressers etc. in Handan Iron & Steel Compel China. The robustness of industrial parameter closed-loop process control systems is improved, and the work quality of the systems bettered.
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