Search2003 Vol. 10, No. 6
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2003, vol. 10, no. 6, pp.
1-4.
Abstract:
Yima Coal Corporation is considering to adopt highwall mining method with auger machine to recover coal from north surface pit that has reached final highwall position. The major geomechanical issues associated with auger mining are highwall and pillar stability. Based on the field investigation and laboratory test results of mechanical parameters, numerical modeling is carried out to assess the stability of highwall and pillar. Field measurements of highwall deformation have been used to validate and ensure the confidence for the development of realistic models. The results of numerical modeling show that the mining method is feasible for mining the seam of 10 m thickness in north surface coal mine.
Yima Coal Corporation is considering to adopt highwall mining method with auger machine to recover coal from north surface pit that has reached final highwall position. The major geomechanical issues associated with auger mining are highwall and pillar stability. Based on the field investigation and laboratory test results of mechanical parameters, numerical modeling is carried out to assess the stability of highwall and pillar. Field measurements of highwall deformation have been used to validate and ensure the confidence for the development of realistic models. The results of numerical modeling show that the mining method is feasible for mining the seam of 10 m thickness in north surface coal mine.
2003, vol. 10, no. 6, pp.
5-10.
Abstract:
A slope engineering system is a complex system, in which many uncertainties exist, including random uncertainties and fuzzy uncertainties. Traditionally, random uncertainties were often considered, while fuzzy uncertainties were ignored. Therefore,fuzzy-random methods should be proposed. A fuzzy point estimate method was proposed by Dodagoudar, that is, considering the effect of fuzzy-random factors, the fuzzy-random limit state function of slopes is changed to random interval limit state function by the λ level cutting, then the moments of the function can be obtained by the Rosenblueth's method, and the stability state of slopes can be evaluated by synthesizing a group of moments. But in Dodagoudar's method, Rosenblueth's state function is composed of only two kinds of combinations of parameters rather than 2n kinds of combinations. So a modified fuzzy point estimate method is proposed by the authors, and it is used in a slope reliability analysis.
A slope engineering system is a complex system, in which many uncertainties exist, including random uncertainties and fuzzy uncertainties. Traditionally, random uncertainties were often considered, while fuzzy uncertainties were ignored. Therefore,fuzzy-random methods should be proposed. A fuzzy point estimate method was proposed by Dodagoudar, that is, considering the effect of fuzzy-random factors, the fuzzy-random limit state function of slopes is changed to random interval limit state function by the λ level cutting, then the moments of the function can be obtained by the Rosenblueth's method, and the stability state of slopes can be evaluated by synthesizing a group of moments. But in Dodagoudar's method, Rosenblueth's state function is composed of only two kinds of combinations of parameters rather than 2n kinds of combinations. So a modified fuzzy point estimate method is proposed by the authors, and it is used in a slope reliability analysis.
2003, vol. 10, no. 6, pp.
11-15.
Abstract:
Taking the chock shield supports as the object of study, methods for measuring and calculating the external load of powered supports were discussed. Selecting the angle parameters as variables, the simple formulae of interactive computation with respect to the work angles of a powered support were deduced and verified by an example. Furthermore, the formulae determining the magnitude, direction and action point of the external load were put forward. The investigation results have provided a sound basis for the software design of the intelligent instrument for load measuring of powered supports.
Taking the chock shield supports as the object of study, methods for measuring and calculating the external load of powered supports were discussed. Selecting the angle parameters as variables, the simple formulae of interactive computation with respect to the work angles of a powered support were deduced and verified by an example. Furthermore, the formulae determining the magnitude, direction and action point of the external load were put forward. The investigation results have provided a sound basis for the software design of the intelligent instrument for load measuring of powered supports.
2003, vol. 10, no. 6, pp.
16-21.
Abstract:
The upward bubble velocity and the pierce length distributions in a sectional water model of the copper convener in Guixi Smelter in Jiangxi, China, were measured using a two-contact electro-resistivity probe. In the case of using a single tuyere, the bubble velocity distribution along longitudinal direction was similar to that derived from Guassian function. Beyond the center of the longitudinal range, the bubble pierce length exhibited a sudden increase. The upward bubble velocity at a specified location could go up to meters per second. Its probability at a fixed location obeys a lognormal function; the bubble pierce length there varies bellow a few centimeters. In the case of using multi-tuyeres, the upward bubble velocity was roughly uniform right above the tuyeres and showed a slow decrease beyond this region. The bubble pierce length within both of these two regions was roughly uniform. Its average value in the former region, however, was found to be somewhat lower than that in the later.
The upward bubble velocity and the pierce length distributions in a sectional water model of the copper convener in Guixi Smelter in Jiangxi, China, were measured using a two-contact electro-resistivity probe. In the case of using a single tuyere, the bubble velocity distribution along longitudinal direction was similar to that derived from Guassian function. Beyond the center of the longitudinal range, the bubble pierce length exhibited a sudden increase. The upward bubble velocity at a specified location could go up to meters per second. Its probability at a fixed location obeys a lognormal function; the bubble pierce length there varies bellow a few centimeters. In the case of using multi-tuyeres, the upward bubble velocity was roughly uniform right above the tuyeres and showed a slow decrease beyond this region. The bubble pierce length within both of these two regions was roughly uniform. Its average value in the former region, however, was found to be somewhat lower than that in the later.
2003, vol. 10, no. 6, pp.
22-25.
Abstract:
The first imported off-gas analysis system on 150 t BOF at Benxi Plates Co. Ltd. is presented and the continuous determination of bath carbon content has been studied. The comparison between the whole-course carbon integral model and the end-point carbon prediction model has been made. The results show that the regular change of CO, CO2 and N2 content in the off-gas during blowing plays an important role in judging the smelting end-point of converter; the cubic curve fitting model has a higher hit rate over 95% for the heats whose end-point carbon content is lower than 0.10% with a precision of ±0.02% and has a large error for the heats whose end-point carbon content is more than 0.15%.
The first imported off-gas analysis system on 150 t BOF at Benxi Plates Co. Ltd. is presented and the continuous determination of bath carbon content has been studied. The comparison between the whole-course carbon integral model and the end-point carbon prediction model has been made. The results show that the regular change of CO, CO2 and N2 content in the off-gas during blowing plays an important role in judging the smelting end-point of converter; the cubic curve fitting model has a higher hit rate over 95% for the heats whose end-point carbon content is lower than 0.10% with a precision of ±0.02% and has a large error for the heats whose end-point carbon content is more than 0.15%.
2003, vol. 10, no. 6, pp.
26-29.
Abstract:
Two-dimension unsteady heat transfer model was applied to obtain the surface temperature and the shell thickness of continuous casting slabs during the process of solidification. On the basis of which, the mathematical model of strain at the interface of solid and liquid steel was set up. Through which, the strain in the solidifying shell under normal and abnormal operation conditions was gained. The results indicate that the strain is small under the normal operation conditions and the internal crack never happens.However, when the variation of the roll gap is above 2 mm, the strain caused by which is greater than that caused by bulging. Furthermore, the total strain exceeds the critical one and the internal crack is the result. So it is of great importance to maintain the fine state of continuous casting machine to avoid the appearance of internal crack.
Two-dimension unsteady heat transfer model was applied to obtain the surface temperature and the shell thickness of continuous casting slabs during the process of solidification. On the basis of which, the mathematical model of strain at the interface of solid and liquid steel was set up. Through which, the strain in the solidifying shell under normal and abnormal operation conditions was gained. The results indicate that the strain is small under the normal operation conditions and the internal crack never happens.However, when the variation of the roll gap is above 2 mm, the strain caused by which is greater than that caused by bulging. Furthermore, the total strain exceeds the critical one and the internal crack is the result. So it is of great importance to maintain the fine state of continuous casting machine to avoid the appearance of internal crack.
2003, vol. 10, no. 6, pp.
30-34.
Abstract:
The transfer of mass flow between ironmaking and steelmaking process at Baoshan Iron and Steel Co. Ltd. has been analyzed. The mathematic-physical models of transport scheduling for hot metal manufacturing have been researched combined with the practical problem in the metallurgical manufacture procedure. Taking into account these models, the scheduling software has been designed, programmed and tested on-line. The new automation system of production scheduling has been implemented successfully at Baosteel, which produces a great economic benefit.
The transfer of mass flow between ironmaking and steelmaking process at Baoshan Iron and Steel Co. Ltd. has been analyzed. The mathematic-physical models of transport scheduling for hot metal manufacturing have been researched combined with the practical problem in the metallurgical manufacture procedure. Taking into account these models, the scheduling software has been designed, programmed and tested on-line. The new automation system of production scheduling has been implemented successfully at Baosteel, which produces a great economic benefit.
2003, vol. 10, no. 6, pp.
35-39.
Abstract:
The preparation and rolling of the semi-solid slurry 1Cr18Ni9Ti stainless steel were researched. The experimental results show that when stirred for 2-3 min under the given test condition, the semi-solid slurry with about 50%-60% (volume fraction) solid and the spherical primary austenitic grains in the size of 100-200 μm can be obtained, and it is easy to be discharged from the bottom little hole of the stirring chamber. The semi-solid slurry of 1Cr18Ni9Ti stainless steel can be rolled into the given plate successfully.However, the solid phase and liquid phase are easily separated in the rolling process, so that the solid primary austenitic grains are concentrated in the center and the liquid phase is near the edge of the rolled plate. The strengths of the plate rolled in the semi-solid state are higher than that of the traditionally repeated hot-rolled plate of 1Cr18Ni9Ti stainless steel.
The preparation and rolling of the semi-solid slurry 1Cr18Ni9Ti stainless steel were researched. The experimental results show that when stirred for 2-3 min under the given test condition, the semi-solid slurry with about 50%-60% (volume fraction) solid and the spherical primary austenitic grains in the size of 100-200 μm can be obtained, and it is easy to be discharged from the bottom little hole of the stirring chamber. The semi-solid slurry of 1Cr18Ni9Ti stainless steel can be rolled into the given plate successfully.However, the solid phase and liquid phase are easily separated in the rolling process, so that the solid primary austenitic grains are concentrated in the center and the liquid phase is near the edge of the rolled plate. The strengths of the plate rolled in the semi-solid state are higher than that of the traditionally repeated hot-rolled plate of 1Cr18Ni9Ti stainless steel.
2003, vol. 10, no. 6, pp.
40-43.
Abstract:
A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural frequencies and mode shapes of the blade for the helicopter are studied by using beam characteristic orthogonal polynomials by the Rayleigh-Ritz method. The variation of natural frequencies with the speed of rotation and the mode shapes at different rotational speeds are plotted. The using of orthogonal polynomials for the bending shapes enables the computation of higher natural frequencies of any order to be accomplished without facing any difficulties.
A rotor manipulation mechanism for micro unmanned helicopter utilizing the inertia and the elasticity of the rotor is introduced. The lagging motion equation of the rotor blades is established, and then the natural frequencies and mode shapes of the blade for the helicopter are studied by using beam characteristic orthogonal polynomials by the Rayleigh-Ritz method. The variation of natural frequencies with the speed of rotation and the mode shapes at different rotational speeds are plotted. The using of orthogonal polynomials for the bending shapes enables the computation of higher natural frequencies of any order to be accomplished without facing any difficulties.
2003, vol. 10, no. 6, pp.
44-47.
Abstract:
According to the actual working conditions of roller shell in the process of continuous roll casting, the Fourier heat transfer law is used to conduct the simulating analysis for the temperature distribution of the roller shell under the condition of periodic thermal shock. The temperature variation law inside the roller shell is studied during the process of continuous roll casting, and the steady temperature distributions of the roller shell at different casting velocities have been obtained when the thermal contact conductance between the roller shell and the casting strip is considered.
According to the actual working conditions of roller shell in the process of continuous roll casting, the Fourier heat transfer law is used to conduct the simulating analysis for the temperature distribution of the roller shell under the condition of periodic thermal shock. The temperature variation law inside the roller shell is studied during the process of continuous roll casting, and the steady temperature distributions of the roller shell at different casting velocities have been obtained when the thermal contact conductance between the roller shell and the casting strip is considered.
2003, vol. 10, no. 6, pp.
48-51.
Abstract:
The PHBV (β-hydroxybutyrate-co-β-hydroxyvalerate) foams as oil sorbent materials, which were prepared by salting out method based on PHBV and chloroform additive and their oil pick-up abilities were investigated. And the oil pick-up abilities of different PHBV foams as oil sorbent materials were compared. The results show that with the amount of chloroform additive and sodium chloride increasing, the oil pick-up rates, the oil-keeping rates and the second oil pick-up rates of PHBV foams can increase to different extent. When the amount of sodium chloride was 92%, the ratio of PHBV to chloroform was 1 (g):14 (mL), the oil pick-up ability of the PHBV foam was optimal. And their oil pick-up ratios can reach 25.51 (26℃) and 27.51 g/g (17℃) in raw oil, which were 4-5 times more than those of PHBV powder. In addition, the structure-modified PHBV as oil sorbent materials also has some advantages, such as three-dimension structure, bio-degradability and good oil pick-up ability, so this kind of green oil sorbent materials will have great perspective in the future.
The PHBV (β-hydroxybutyrate-co-β-hydroxyvalerate) foams as oil sorbent materials, which were prepared by salting out method based on PHBV and chloroform additive and their oil pick-up abilities were investigated. And the oil pick-up abilities of different PHBV foams as oil sorbent materials were compared. The results show that with the amount of chloroform additive and sodium chloride increasing, the oil pick-up rates, the oil-keeping rates and the second oil pick-up rates of PHBV foams can increase to different extent. When the amount of sodium chloride was 92%, the ratio of PHBV to chloroform was 1 (g):14 (mL), the oil pick-up ability of the PHBV foam was optimal. And their oil pick-up ratios can reach 25.51 (26℃) and 27.51 g/g (17℃) in raw oil, which were 4-5 times more than those of PHBV powder. In addition, the structure-modified PHBV as oil sorbent materials also has some advantages, such as three-dimension structure, bio-degradability and good oil pick-up ability, so this kind of green oil sorbent materials will have great perspective in the future.
2003, vol. 10, no. 6, pp.
52-56.
Abstract:
Based on the technology of titanium dioxide grafting modification with polystyrene (PS), the modification mechanisms are studied and the polystyrene-grafting states on the surface of titanium dioxide have been set up. Under the synergistic actions of mechanical force, chemistry and heat, macromolecular free radicals of PS are created, at the same time, the O-O bonds of titanium dioxide are broken and the oxide free radicals produced, and the numbers of oxygen atom are increased and crystal lattice defects rich electrons are formed on the surface of titanium dioxide. The radical polymerization is the main reaction between PS and titanium dioxide and C-O bonds form in the process of modification. Multi-sites chemical adsorption also exists besides grafting between PS and titanium dioxide.
Based on the technology of titanium dioxide grafting modification with polystyrene (PS), the modification mechanisms are studied and the polystyrene-grafting states on the surface of titanium dioxide have been set up. Under the synergistic actions of mechanical force, chemistry and heat, macromolecular free radicals of PS are created, at the same time, the O-O bonds of titanium dioxide are broken and the oxide free radicals produced, and the numbers of oxygen atom are increased and crystal lattice defects rich electrons are formed on the surface of titanium dioxide. The radical polymerization is the main reaction between PS and titanium dioxide and C-O bonds form in the process of modification. Multi-sites chemical adsorption also exists besides grafting between PS and titanium dioxide.
2003, vol. 10, no. 6, pp.
57-60.
Abstract:
For some electrochemical systems the traditional data processing methods can not be met, so it is necessary to develop a new method to deal with these problems. When processing the electrochemical AC impedance data of titanium alloy TAl2 in 3% NaCl solution (at free corrosion potential, room temperature) a new method is developed which can detach the information of the interface resistance demonstrably from the interface capacitance. The results show that the interface resistance and capacitance are all functions of frequency. And the AC impedance of the resistance and capacitance obey the following relations:C(f)=104.01982 f-0.9292,R(f)=104.80011 (f+0.008)-0.90897, which is completely different from the traditional conception that the interface resistance and capacitance are constants. And this phenomenon is ubiquitous in titanium alloys according to the study. So perhaps it is an innate characteristic of interface.
For some electrochemical systems the traditional data processing methods can not be met, so it is necessary to develop a new method to deal with these problems. When processing the electrochemical AC impedance data of titanium alloy TAl2 in 3% NaCl solution (at free corrosion potential, room temperature) a new method is developed which can detach the information of the interface resistance demonstrably from the interface capacitance. The results show that the interface resistance and capacitance are all functions of frequency. And the AC impedance of the resistance and capacitance obey the following relations:C(f)=104.01982 f-0.9292,R(f)=104.80011 (f+0.008)-0.90897, which is completely different from the traditional conception that the interface resistance and capacitance are constants. And this phenomenon is ubiquitous in titanium alloys according to the study. So perhaps it is an innate characteristic of interface.
2003, vol. 10, no. 6, pp.
61-66.
Abstract:
The present study aims at developing the high speed steel (HSS) as roll materials to replace the traditional roll materials such as the alloy cast iron and powder metallurgical (PM) hard alloy. The HSS roll billet was formed by centrifugal casting, and the billet was rough machined after soften annealing heat treatment, then it was quenched and tempered to get suitable hardness and toughness. After that the HSS roll was finish machined to the final dimension of φ285 mm in the outer diameter, φ160 mm in the inner diameter and 120 mm in width and its surface hardness was tested. Finally the HSS roll was used in high speed wire rod mill. The test results show that a high and homogeneous hardness can obtain on the work surface of HSS rolls, the surface hardness is 63-65HRC and its variation is smaller than 2HRC. The impact toughness of this kind of HSS is about 16 J/cm2. The results of on-line service investigation in high speed wire rod mill indicate that the HSS rolls have excellent wear resistance, the steel rolling quantity per mm of HSS rolls is 3120 t, the service life-span of HSS rolls is 4 times longer than that of high chromium cast iron rolls and it is close to that of the PM hard alloy rolls. The manufacturing burden of HSS rolls is obviously lower than that of the PM hard alloy rolls, it is only 25% of that of the PM hard alloy rolls.
The present study aims at developing the high speed steel (HSS) as roll materials to replace the traditional roll materials such as the alloy cast iron and powder metallurgical (PM) hard alloy. The HSS roll billet was formed by centrifugal casting, and the billet was rough machined after soften annealing heat treatment, then it was quenched and tempered to get suitable hardness and toughness. After that the HSS roll was finish machined to the final dimension of φ285 mm in the outer diameter, φ160 mm in the inner diameter and 120 mm in width and its surface hardness was tested. Finally the HSS roll was used in high speed wire rod mill. The test results show that a high and homogeneous hardness can obtain on the work surface of HSS rolls, the surface hardness is 63-65HRC and its variation is smaller than 2HRC. The impact toughness of this kind of HSS is about 16 J/cm2. The results of on-line service investigation in high speed wire rod mill indicate that the HSS rolls have excellent wear resistance, the steel rolling quantity per mm of HSS rolls is 3120 t, the service life-span of HSS rolls is 4 times longer than that of high chromium cast iron rolls and it is close to that of the PM hard alloy rolls. The manufacturing burden of HSS rolls is obviously lower than that of the PM hard alloy rolls, it is only 25% of that of the PM hard alloy rolls.
2003, vol. 10, no. 6, pp.
67-71.
Abstract:
Finding the optimal algorithm between an efficient encoding process and the rate distortion is the main research in fractal image compression theory. A new method has been proposed based on the optimization of the Least-Square Error and the orthogonal projection. A large number of domain blocks can be eliminated in order to speed-up fractal image compression. Moreover, since the rate-distortion performance of most fractal image coders is not satisfactory, an efficient bit allocation algorithm to improve the rate distortion is also proposed. The implementation and comparison have been done with the feature extraction method to prove the efficiency of the proposed method.
Finding the optimal algorithm between an efficient encoding process and the rate distortion is the main research in fractal image compression theory. A new method has been proposed based on the optimization of the Least-Square Error and the orthogonal projection. A large number of domain blocks can be eliminated in order to speed-up fractal image compression. Moreover, since the rate-distortion performance of most fractal image coders is not satisfactory, an efficient bit allocation algorithm to improve the rate distortion is also proposed. The implementation and comparison have been done with the feature extraction method to prove the efficiency of the proposed method.
2003, vol. 10, no. 6, pp.
72-75.
Abstract:
Chaos synchronization has been applied in secure communication, chemical reaction, biological systems, and information processing. A new theorem to synchronization of unified chaotic systems via adaptive control is proposed. The consutructive theorem provides the design scheme for adaptive controller such that a respond system can synchronize with respect to an uncertain drive system. One example for discontinuous chaotic system is proposed to illustrate the effectiveness and feasibility.
Chaos synchronization has been applied in secure communication, chemical reaction, biological systems, and information processing. A new theorem to synchronization of unified chaotic systems via adaptive control is proposed. The consutructive theorem provides the design scheme for adaptive controller such that a respond system can synchronize with respect to an uncertain drive system. One example for discontinuous chaotic system is proposed to illustrate the effectiveness and feasibility.
2003, vol. 10, no. 6, pp.
76-79.
Abstract:
In order to provide a theoretic basis for the research of Ti(CxNy) thin films, the thermodynamic database of Ti-C-N ternary system is established and the phase diagram sections are calculated. In addition to the assessed thermodynamic properties of Ti-C-N system, the influence of the residual strain energy of Ti(CxNy) thin films on the phase equilibria is analyzed. The classical formula for calculating the elastic strain energy is expressed into a Redlich-Kister form in order to perform the thermodynamic and equilibrium calculations using the Thermo-Calc software. Isothermal sections at 900 and 1100 K are calculated with this database and compared with those calculated without considering the residual stress. As a result, with the addition of strain energy δ-fcc Ti(CxNy) phase area shrinks. It is therefore concluded that with the influence of the residual stress in Ti(CxNy) thin solid film, the precipitation of pure δ film requires more precise control of composition.
In order to provide a theoretic basis for the research of Ti(CxNy) thin films, the thermodynamic database of Ti-C-N ternary system is established and the phase diagram sections are calculated. In addition to the assessed thermodynamic properties of Ti-C-N system, the influence of the residual strain energy of Ti(CxNy) thin films on the phase equilibria is analyzed. The classical formula for calculating the elastic strain energy is expressed into a Redlich-Kister form in order to perform the thermodynamic and equilibrium calculations using the Thermo-Calc software. Isothermal sections at 900 and 1100 K are calculated with this database and compared with those calculated without considering the residual stress. As a result, with the addition of strain energy δ-fcc Ti(CxNy) phase area shrinks. It is therefore concluded that with the influence of the residual stress in Ti(CxNy) thin solid film, the precipitation of pure δ film requires more precise control of composition.
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