Search2004 Vol. 11, No. 5
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2004, vol. 11, no. 5, pp.
385-388.
Abstract:
Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.
Bioflotation of pyrite with bacteria Thiobacillus ferrooxidans in the presence or absence of potassium ethyl xanthate was studied on a pure pyrite through microflotation and electrophoretic light scattering measurements. The experimental results showed that in the absence of xanthate, pyrite flotation is slightly enhanced by Thiobacillus ferrooxidans. However, with xanthate as a collector, pyrite flotation is strongly depressed after being exposed to the bacteria. The longer is the time when the pyrite is exposed to the bacteria, the stronger the depression is. The mechanism of the depression might be due to the formation of the biofilms of Thiobacillus ferrooxidans on pyrite surfaces, preventing the adsorption of xanthate on pyrite surfaces in the form of dixanthogen or xanthate ions.
2004, vol. 11, no. 5, pp.
389-393.
Abstract:
In order to increase production efficiency at open-pit mines, on the basis of linear programming, a practical mathematical model for optimizing truck flow was developed, which improved the traditional fixed manual schedule method. The model has advantages from linear programming and objective programming, makes most handling points working at full capacity and keeps an optimized ratio between trucks and excavators. For ensuring feasibility of the model in practical production, four standards for feasibility test were proposed. The model satisfied all the standards. The application in a large scale open-pit iron mine indicated that the model reduced the number of required trucks by 10% compared with the fixed manual schedule method.
In order to increase production efficiency at open-pit mines, on the basis of linear programming, a practical mathematical model for optimizing truck flow was developed, which improved the traditional fixed manual schedule method. The model has advantages from linear programming and objective programming, makes most handling points working at full capacity and keeps an optimized ratio between trucks and excavators. For ensuring feasibility of the model in practical production, four standards for feasibility test were proposed. The model satisfied all the standards. The application in a large scale open-pit iron mine indicated that the model reduced the number of required trucks by 10% compared with the fixed manual schedule method.
2004, vol. 11, no. 5, pp.
394-397.
Abstract:
The effect and mechanism of the removal of Pb2+ from an aqueous solution by using brucite as the adsorbent were studied.It was revealed that the increase in pH of brucite suspension, as a result of the release of magnesium hydroxide into the suspension,leads to a sharp rise of the adsorption amount of Pb2+ on brucite. The synergism of buffering and adsorption capacities of brucite is responsible for the removal of Pb2+ from the aqueous solution. The coexistence of Cu2+ with Pb2+ causes a decrease of their adsorption on brucite due to a competition for surface sites and brucite exhibits a higher adsorption capacity for Pb2+ than for Cu2+. The percentage adsorption of Pb2+ on brucite could reach 96.38%, 97.20% and 94.09% respectively with the initial pH of the suspension pHi = 1.76 (initial Pb2+ concentration [Pb2+]i = 20 μmol/L), 1.82 ([Pb2+]i = 100 μmol/L) and 1.84 ([Pb2+]i = 500 μmol/L). It was concluded that brucite is a very efficient mineral adsorbent for Pb2+ removal from polluted acidic water.
The effect and mechanism of the removal of Pb2+ from an aqueous solution by using brucite as the adsorbent were studied.It was revealed that the increase in pH of brucite suspension, as a result of the release of magnesium hydroxide into the suspension,leads to a sharp rise of the adsorption amount of Pb2+ on brucite. The synergism of buffering and adsorption capacities of brucite is responsible for the removal of Pb2+ from the aqueous solution. The coexistence of Cu2+ with Pb2+ causes a decrease of their adsorption on brucite due to a competition for surface sites and brucite exhibits a higher adsorption capacity for Pb2+ than for Cu2+. The percentage adsorption of Pb2+ on brucite could reach 96.38%, 97.20% and 94.09% respectively with the initial pH of the suspension pHi = 1.76 (initial Pb2+ concentration [Pb2+]i = 20 μmol/L), 1.82 ([Pb2+]i = 100 μmol/L) and 1.84 ([Pb2+]i = 500 μmol/L). It was concluded that brucite is a very efficient mineral adsorbent for Pb2+ removal from polluted acidic water.
2004, vol. 11, no. 5, pp.
398-402.
Abstract:
In order to make clear the formation mechanism of centerline cracks in continuously cast slabs, the form, distribution and other characteristics of the cracks were analyzed. The final solidification point, surface temperature of the slabs and strain in solidifying shell were investigated. The results were that: (1) Five relatively low temperature zones exist on slab surface below the three water spraying nozzles and near the two edges, respectively, which corresponds to the places of centerline cracks and triangle-zone cracks. (2) Centerline cracks and triangle-zone cracks occur because of weak secondary cooling, uneven cooling along slab width,and large variation of roll gap. (3) After minimizing the variation of roll gap and applying the new secondary cooling pattern, the occurring frequency of centerline and triangle-zone cracks minimizes to zero.
In order to make clear the formation mechanism of centerline cracks in continuously cast slabs, the form, distribution and other characteristics of the cracks were analyzed. The final solidification point, surface temperature of the slabs and strain in solidifying shell were investigated. The results were that: (1) Five relatively low temperature zones exist on slab surface below the three water spraying nozzles and near the two edges, respectively, which corresponds to the places of centerline cracks and triangle-zone cracks. (2) Centerline cracks and triangle-zone cracks occur because of weak secondary cooling, uneven cooling along slab width,and large variation of roll gap. (3) After minimizing the variation of roll gap and applying the new secondary cooling pattern, the occurring frequency of centerline and triangle-zone cracks minimizes to zero.
2004, vol. 11, no. 5, pp.
403-405.
Abstract:
In order to take data information from the slag property diagram in a ternary system automatically and actually, a picture recognition and drawing software has been developed by Visual Basic 6.0 based on the image coding principle of computer system and the graphics programming method of VB. This software can transform the ternary system isopleth diagram from bitmap format to data file and establish a corresponding database which can be applied to rapidly retrieve a mass of data and make correlative thermodynamics or kinetics calculation. Besides, it still has the function of drawing the ternary system diagram which can draw different kinds of property parameters in the same diagram.
In order to take data information from the slag property diagram in a ternary system automatically and actually, a picture recognition and drawing software has been developed by Visual Basic 6.0 based on the image coding principle of computer system and the graphics programming method of VB. This software can transform the ternary system isopleth diagram from bitmap format to data file and establish a corresponding database which can be applied to rapidly retrieve a mass of data and make correlative thermodynamics or kinetics calculation. Besides, it still has the function of drawing the ternary system diagram which can draw different kinds of property parameters in the same diagram.
2004, vol. 11, no. 5, pp.
406-410.
Abstract:
The activity model of CaO-FeO-SiO2-MoO3 quarternary system was established according to the coexistence theory of slag structure and the reduction thermodynamics of molybdenum oxide was discussed by applying this model. The activities of SiO2and MoOs decrease, while that of CaO increases with increasing the basicity of slag. Among SiC, [C] and [Si] reactants, the reducing capability of SiC is the strongest, while that of [C] is the poorest at a high temperature (about 1873 K). It is advantageous to increase the yield of molybdenum by increasing the content of [Si] or [C]. Controlling of basicity of slag can prevent the oxidation loss of molybdenum.
The activity model of CaO-FeO-SiO2-MoO3 quarternary system was established according to the coexistence theory of slag structure and the reduction thermodynamics of molybdenum oxide was discussed by applying this model. The activities of SiO2and MoOs decrease, while that of CaO increases with increasing the basicity of slag. Among SiC, [C] and [Si] reactants, the reducing capability of SiC is the strongest, while that of [C] is the poorest at a high temperature (about 1873 K). It is advantageous to increase the yield of molybdenum by increasing the content of [Si] or [C]. Controlling of basicity of slag can prevent the oxidation loss of molybdenum.
2004, vol. 11, no. 5, pp.
411-414.
Abstract:
The grain growth behavior in reactive spray formed 7075+2.91vol%TiC Al alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. The effects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were also investigated. The specimens were heat-treated isothermally at various temperatures between the solidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water. The microstructure of reheated specimens was characterized using scanning electron microscopy and optical microscopy. The grain size was measured using a mean linear intercept method.Results show that the in-situ TiC particles can effectively retard grain growth and refine the grain at a limited size. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates that the in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solid state.
The grain growth behavior in reactive spray formed 7075+2.91vol%TiC Al alloy was studied and compared with that of spray formed 7075 Al alloy at semi-solid state. The effects of in-situ TiC particles on the microstructure of spray formed 7075 Al alloy were also investigated. The specimens were heat-treated isothermally at various temperatures between the solidus and liquidus of 7075 Al alloy for times in the range of 10-60 min, then quenched in water. The microstructure of reheated specimens was characterized using scanning electron microscopy and optical microscopy. The grain size was measured using a mean linear intercept method.Results show that the in-situ TiC particles can effectively retard grain growth and refine the grain at a limited size. The grain growth exponent in Arrhenius equation increases from 2 to 3, which indicates that the in-situ TiC particles have the significant pinning effect on grain coarsening in the semi-solid state.
2004, vol. 11, no. 5, pp.
415-419.
Abstract:
Au films with a thickness of about 300 nm were deposited on SiO2/Si(100) and mica substrates by dc sputtering. X-ray diffraction spectroscopy and field emission scanning electron microscopy were used to analyze the structure and internal stress of the Au films. The films grown on SiO2/Si(100) show a preferential orientation of [111] in the growth direction. However the films grown on mica have mixture crystalline orientations of [111], [200], [220] and [311] in the growth direction and the orientations of [200] and [311] are slightly more than those of [111] and [220]. An internal stress in the films grown on SiO2/Si(100) is tensile. For Au films grown on mica the internal stresses in the [111]- and [311]-orientation grains are compressive while those in the [200]- and [220]-orientation grains are tensile. Au films grown SiOJSi(100) have some very large grains with a size of about 400 nm and have a wider grain size distribution compared with those grown on mica.
Au films with a thickness of about 300 nm were deposited on SiO2/Si(100) and mica substrates by dc sputtering. X-ray diffraction spectroscopy and field emission scanning electron microscopy were used to analyze the structure and internal stress of the Au films. The films grown on SiO2/Si(100) show a preferential orientation of [111] in the growth direction. However the films grown on mica have mixture crystalline orientations of [111], [200], [220] and [311] in the growth direction and the orientations of [200] and [311] are slightly more than those of [111] and [220]. An internal stress in the films grown on SiO2/Si(100) is tensile. For Au films grown on mica the internal stresses in the [111]- and [311]-orientation grains are compressive while those in the [200]- and [220]-orientation grains are tensile. Au films grown SiOJSi(100) have some very large grains with a size of about 400 nm and have a wider grain size distribution compared with those grown on mica.
2004, vol. 11, no. 5, pp.
420-424.
Abstract:
TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited on high speed steel substrates by using a filtered cathodic vacuum arc technique. The structure and composition of the coatings were characterized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests for the multilayered coatings. Nanoindentation tests were performed to determine the hardness and elastic modulus of the coatings as a function of the multiplayer modulation period. It was observed that the hardness of the multilayered coatings is higher than those of either TiN or CrN single coatings, and it increases with decreasing modulation periods, which is consistent with predictions from the Hall-Perch type strengthening mechanism, though at small modulation periods, deviation from the Hall-Petch relation has been observed for the multilayered coatings. The life-span of drills coated with TiN/CrN multilayered is triple as long as that coated with TiN layer.
TiN/CrN multilayered hard coatings with TiCrN interlayer were deposited on high speed steel substrates by using a filtered cathodic vacuum arc technique. The structure and composition of the coatings were characterized by scanning electron microscopy (SEM) and Auger electron spectroscopy (AES). A high adhesion of up to 80 N was demonstrated by scratching tests for the multilayered coatings. Nanoindentation tests were performed to determine the hardness and elastic modulus of the coatings as a function of the multiplayer modulation period. It was observed that the hardness of the multilayered coatings is higher than those of either TiN or CrN single coatings, and it increases with decreasing modulation periods, which is consistent with predictions from the Hall-Perch type strengthening mechanism, though at small modulation periods, deviation from the Hall-Petch relation has been observed for the multilayered coatings. The life-span of drills coated with TiN/CrN multilayered is triple as long as that coated with TiN layer.
2004, vol. 11, no. 5, pp.
425-427.
Abstract:
Based on experimental data of positron annihilation technology, electrolytic dissolution technique, electron back-scattered pattern, etc. And by analysis the strengthening factors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP (Compact Strip Production) technique was investigated. The value of each strengthening mechanism and its contribution percentage to yield strength were achieved. The results show that refinement strengthening is the predominant strengthening mode; precipitation strengthening and dislocation strengthening are second to it, their contributions to yield strength are almost equal.
Based on experimental data of positron annihilation technology, electrolytic dissolution technique, electron back-scattered pattern, etc. And by analysis the strengthening factors, the strengthening mechanism of ultra-thin hot strip of low carbon steel produced by CSP (Compact Strip Production) technique was investigated. The value of each strengthening mechanism and its contribution percentage to yield strength were achieved. The results show that refinement strengthening is the predominant strengthening mode; precipitation strengthening and dislocation strengthening are second to it, their contributions to yield strength are almost equal.
2004, vol. 11, no. 5, pp.
428-432.
Abstract:
An aerosol process for making aluminum nitride nano-powder by decomposition of single compound diethylaluminun azide was described. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study characters of the AIN powder. It is shown that the process can produce spherical AIN powder with mean particle diameters ranging from 10 to 50 nm at 500-800°C. The generated amorphous AIN powder is characterized by a BET (Brunauer-Emmett-Teller) surface area of 103 m2/g and is very reactive to moisture.
An aerosol process for making aluminum nitride nano-powder by decomposition of single compound diethylaluminun azide was described. X-ray diffraction (XRD) and transmission electron microscopy (TEM) were used to study characters of the AIN powder. It is shown that the process can produce spherical AIN powder with mean particle diameters ranging from 10 to 50 nm at 500-800°C. The generated amorphous AIN powder is characterized by a BET (Brunauer-Emmett-Teller) surface area of 103 m2/g and is very reactive to moisture.
2004, vol. 11, no. 5, pp.
433-441.
Abstract:
The effects of SO2 on the initial atmospheric corrosion of AZ91D magnesium alloy were investigated in laboratory. Metallographic observation, SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Proton Spectrograph) were used to analyze and discuss the initial surface morphology of corrosion layers and corrosion products. The corrosion rate of the alloy increases with increasing the content of SO2. The initial attack has the characteristics of localized corrosion and preferentially concentrates on α phase. MgO and Mg(OH)2 form at first, which provide a protective layer, then the existence of SO2 decreases the pH of the thin solution on the alloy, accelerates dissolution process, and promotes the formation of MgSO3·6H20 and MgSO4·6H20,meanwhile cracks were found on the corrosion products with corrosion continuation. These soluble corrosion products and the cracks provide the paths for filtering oxygen and corrosion pollutants into the matrix, which results in severe localized corrosion and the loss of protective function of film.
The effects of SO2 on the initial atmospheric corrosion of AZ91D magnesium alloy were investigated in laboratory. Metallographic observation, SEM (Scanning Electron Microscopy), XRD (X-ray Diffraction) and XPS (X-ray Proton Spectrograph) were used to analyze and discuss the initial surface morphology of corrosion layers and corrosion products. The corrosion rate of the alloy increases with increasing the content of SO2. The initial attack has the characteristics of localized corrosion and preferentially concentrates on α phase. MgO and Mg(OH)2 form at first, which provide a protective layer, then the existence of SO2 decreases the pH of the thin solution on the alloy, accelerates dissolution process, and promotes the formation of MgSO3·6H20 and MgSO4·6H20,meanwhile cracks were found on the corrosion products with corrosion continuation. These soluble corrosion products and the cracks provide the paths for filtering oxygen and corrosion pollutants into the matrix, which results in severe localized corrosion and the loss of protective function of film.
2004, vol. 11, no. 5, pp.
442-448.
Abstract:
The experiments were carried out to measure the mechanical properties of three grades of structural steels (Q235A, 16Mn and Q390E steel ) at low temperature. It was shown that the strength of the steels increases while the plasticity and toughness decrease as temperature drops. In the transitional area the toughness drops rapidly with temperature. Among the three structural steels,Q390E steel has the best toughness and the lowest sensitivity.
The experiments were carried out to measure the mechanical properties of three grades of structural steels (Q235A, 16Mn and Q390E steel ) at low temperature. It was shown that the strength of the steels increases while the plasticity and toughness decrease as temperature drops. In the transitional area the toughness drops rapidly with temperature. Among the three structural steels,Q390E steel has the best toughness and the lowest sensitivity.
2004, vol. 11, no. 5, pp.
449-454.
Abstract:
Nanoparticle hydroxyapatite was prepared by a wet chemical precipitation method. The effects of different synthesis conditions, i.e. Contents of reagents (0.2, 0.5 and 0.8 mol/L), reaction temperatures (20, 37, 55 and 75℃) and reaction time (0-24 h),were studied based on crystallization process analysis and the effects of washing methods (with water or alcohol) were also studied.Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED) and inductively coupled plasma spectroscopy (ICP) were used to characterize the powders. Chemical analysis shows that the purity of the precipitated hydroxyapatite largely depends on reaction time. X-ray diffraction and TEM micrographs results show that reaction temperature is a key factor affecting crystallinity, morphology and particle size. Degree of supersaturation and stirring also affects the crystallization. Particles are in a shape of short rod and have a size of 20-40 nm in length at 20℃ and 37℃,but acicular morphology and a size of 150-170 nm in length at 75℃. Particles are monocrystalline at 20℃ and 37℃, and are polycrystalline at 55℃ and 75℃. The results show that stoichiometry hydroxyapatite with controlled particle size, morphology and crystallinity can be obtained by carefully controlling the reaction conditions.
Nanoparticle hydroxyapatite was prepared by a wet chemical precipitation method. The effects of different synthesis conditions, i.e. Contents of reagents (0.2, 0.5 and 0.8 mol/L), reaction temperatures (20, 37, 55 and 75℃) and reaction time (0-24 h),were studied based on crystallization process analysis and the effects of washing methods (with water or alcohol) were also studied.Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), electron diffraction (ED) and inductively coupled plasma spectroscopy (ICP) were used to characterize the powders. Chemical analysis shows that the purity of the precipitated hydroxyapatite largely depends on reaction time. X-ray diffraction and TEM micrographs results show that reaction temperature is a key factor affecting crystallinity, morphology and particle size. Degree of supersaturation and stirring also affects the crystallization. Particles are in a shape of short rod and have a size of 20-40 nm in length at 20℃ and 37℃,but acicular morphology and a size of 150-170 nm in length at 75℃. Particles are monocrystalline at 20℃ and 37℃, and are polycrystalline at 55℃ and 75℃. The results show that stoichiometry hydroxyapatite with controlled particle size, morphology and crystallinity can be obtained by carefully controlling the reaction conditions.
2004, vol. 11, no. 5, pp.
455-461.
Abstract:
A numerical analysis of the laser drying process by employing a generalized, Maxwell-Cattaneo equation to treat both heat and mass transfer was presented. Calculations were performed to illustrate the non-classical transport of heat and moisture. The effect of the heat flux density and the initial moisture content on water removal was also investigated. The results indicate that the nonequilibrium mass diffusion plays an important role during the very early stages of moisture removal, especially at the surface of the medium. Away from the surface, the non-Fickian model shows a delay in the reduction of the moisture content. The calculation resuits also show that the initial moisture content of the medium has a considerable effect on water removal.
A numerical analysis of the laser drying process by employing a generalized, Maxwell-Cattaneo equation to treat both heat and mass transfer was presented. Calculations were performed to illustrate the non-classical transport of heat and moisture. The effect of the heat flux density and the initial moisture content on water removal was also investigated. The results indicate that the nonequilibrium mass diffusion plays an important role during the very early stages of moisture removal, especially at the surface of the medium. Away from the surface, the non-Fickian model shows a delay in the reduction of the moisture content. The calculation resuits also show that the initial moisture content of the medium has a considerable effect on water removal.
2004, vol. 11, no. 5, pp.
462-468.
Abstract:
A method of fuzzy identification based on T-S fuzzy model was proposed for predicting temperature Ms from chemical composition, austenitizing temperature and time for low alloy steel. The degree of membership of each sample was calculated with fuzzy clustering algorithm. Kalman filtering was used to identify the consequent parameters. Compared with the results obtained by empirical models based on the same data, the results by the fuzzy method showed good precision. The accuracy of the fuzzy model is almost 6 times higher than that of the best empirical model. The influence of alloying elements, austenitizing temperature and time on Ms was analyzed quantitatively by using the fuzzy model. It is shown that there exists a nonlinear relationship between the contents of alloying elements in steels and their Ms, and the effects of austenltizing temperature and time on Ms temperature cannot be neglected.
A method of fuzzy identification based on T-S fuzzy model was proposed for predicting temperature Ms from chemical composition, austenitizing temperature and time for low alloy steel. The degree of membership of each sample was calculated with fuzzy clustering algorithm. Kalman filtering was used to identify the consequent parameters. Compared with the results obtained by empirical models based on the same data, the results by the fuzzy method showed good precision. The accuracy of the fuzzy model is almost 6 times higher than that of the best empirical model. The influence of alloying elements, austenitizing temperature and time on Ms was analyzed quantitatively by using the fuzzy model. It is shown that there exists a nonlinear relationship between the contents of alloying elements in steels and their Ms, and the effects of austenltizing temperature and time on Ms temperature cannot be neglected.
2004, vol. 11, no. 5, pp.
469-473.
Abstract:
Cu-Zn-Al alloy of one dimensional nano-structure was prepared and the structure of obtained nano-material was characterized by transmission electron microscope (TEM). It was shown that there are non-linear oscillations on the surface of Cu-Zn-Al alloy and the consanguineous connection exists between non-linear oscillation and the growth process of one dimensional nano-structure. The diameter of one dimensional nano-structure is about 40 nm, and the ratio of length to diameter is over 40. Finally, the growth mechanism of one dimensional nano-structure was also studied.
Cu-Zn-Al alloy of one dimensional nano-structure was prepared and the structure of obtained nano-material was characterized by transmission electron microscope (TEM). It was shown that there are non-linear oscillations on the surface of Cu-Zn-Al alloy and the consanguineous connection exists between non-linear oscillation and the growth process of one dimensional nano-structure. The diameter of one dimensional nano-structure is about 40 nm, and the ratio of length to diameter is over 40. Finally, the growth mechanism of one dimensional nano-structure was also studied.
2004, vol. 11, no. 5, pp.
474-476.
Abstract:
A combustion synthesis method was adapted for the efficient preparation of pure zinc ferrite particles (ZnFe2O4). It is based on the exothermic reaction of the corresponding metal nitrates with a reducing agent, to produce extremely fine-grained ashes that readily convert into pure ZnFe2O4 with treating thermally. The composition and microstructure of the so-obtained samples were studied by XRD (X-ray powder diffraction), TEM (Transmission Electron Microscopy) and AFM (Atomic Force Microscopy). These results showed that the range of particle size of ZnFe2O4 is about 15-25 nm. Photocatalytic activities of nanometer ZnFe2O4 were also evaluated by degradation of the curcumin solution.
A combustion synthesis method was adapted for the efficient preparation of pure zinc ferrite particles (ZnFe2O4). It is based on the exothermic reaction of the corresponding metal nitrates with a reducing agent, to produce extremely fine-grained ashes that readily convert into pure ZnFe2O4 with treating thermally. The composition and microstructure of the so-obtained samples were studied by XRD (X-ray powder diffraction), TEM (Transmission Electron Microscopy) and AFM (Atomic Force Microscopy). These results showed that the range of particle size of ZnFe2O4 is about 15-25 nm. Photocatalytic activities of nanometer ZnFe2O4 were also evaluated by degradation of the curcumin solution.
2004, vol. 11, no. 5, pp.
477-479.
Abstract:
A neural network model with a special structure, which is divided into linear and nonlinear parts, was proposed for identification of a nonlinear system. In this model, the nonlinear part of the object is treated as a measured disturbance, and is compensated by a feed forward method; an adaptive pole placement algorithm is used to control the linear part of the object. The simulation results show that the identification efficiency and accuracy are improved when the new controller is applied to sintering finish point control.
A neural network model with a special structure, which is divided into linear and nonlinear parts, was proposed for identification of a nonlinear system. In this model, the nonlinear part of the object is treated as a measured disturbance, and is compensated by a feed forward method; an adaptive pole placement algorithm is used to control the linear part of the object. The simulation results show that the identification efficiency and accuracy are improved when the new controller is applied to sintering finish point control.
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