Mining subsidence pools are water bodies formed by soil subsidence near mines. We studied the impact the surrounding coal production activities and power plants have on these waters by measuring the concentrations of ...Mining subsidence pools are water bodies formed by soil subsidence near mines. We studied the impact the surrounding coal production activities and power plants have on these waters by measuring the concentrations of harmful trace elements in these waters. The concentration of the four elements F, Hg, Se and As increased by 0.92%, 0.78%, 0.70% and 0.81%, respectively, in the Datong mining subsidence pool from November 2004 to November 2006. The four elements increased by 1.58%, 1.23%, 1.08% and 0.92%, respectively, in the Xie’er mining subsidence pool and 1.16%, 1.06%, 1.02% and 1.01%, respectively, in the Pansan mining subsidence pool over the same time period. The absolute levels of F, Hg, Se and As in the pool are related to the background levels of the elements. A close relationship between nearby coal mines and power plants and increasing levels of the measured elements is noted.展开更多
Wireless sensor networks (WSNs) are very important for monitoring underground mine safety. Sensor node deployment affects the performances of WSNs. In our study, a chain-type wireless underground mine sensor network (...Wireless sensor networks (WSNs) are very important for monitoring underground mine safety. Sensor node deployment affects the performances of WSNs. In our study, a chain-type wireless underground mine sensor network (CWUMSN) is first pre- sented. A CWUMSN can monitor the environment and locate miners in underground mines. The lowest density deployment strate- gies of cluster head nodes are discussed theoretically. We prove that the lifetime of CWUMSN with a non-uniform deployment strategy is longer than with a uniform deployment strategy. Secondly, we present the algorithm of non-uniform lowest density de- ployment of cluster head nodes. Next, we propose a dynamic choice algorithm of cluster head nodes for CWUMSN which can im- prove the adaptability of networks. Our experiments of CWUMSN with both non-uniform lowest density and uniform lowest den- sity deployments are simulated. The results show that the lifetime of CWUMSN with non-uniform lowest density deployment is almost 2.5 times as long as that of the uniform lowest density deployment. This work provides a new deployment strategy for wire- less underground mine sensor networks and then effectively promotes the application of wireless sensor networks to underground mines.展开更多
When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stra...When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.展开更多
In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When...In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.展开更多
It is very important to accurately recognize and locate pulverized and block coal seen in a coal mine's infrared image monitoring system. Infrared monitor images of pulverized and block coal were sampled in the ro...It is very important to accurately recognize and locate pulverized and block coal seen in a coal mine's infrared image monitoring system. Infrared monitor images of pulverized and block coal were sampled in the roadway of a coal mine. Texture statistics from the grey level dependence matrix were selected as the criterion for classification. The distributions of the texture statistics were calculated and analysed. A normalizing function was added to the front end of the BP network with one hidden layer. An additional classification layer is joined behind the linear layer. The recognition of pulverized from block coal images was tested using the improved BP network. The results of the experiment show that texture variables from the grey level dependence matrix can act as recognizable features of the image. The innovative improved BP network can then recognize the pulverized and block coal images.展开更多
The Wielandt-Hoffman theorem of the real symmetric matrix is extended into a plural matrix. On the basis of it, a similar theory about the trace of a matrix for the arithmetic mean, geometric mean inequality, Holder i...The Wielandt-Hoffman theorem of the real symmetric matrix is extended into a plural matrix. On the basis of it, a similar theory about the trace of a matrix for the arithmetic mean, geometric mean inequality, Holder inequality and Minkowski inequality is proved.展开更多
Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane f...Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane fouling were investigated and the measure was put forward for optimum operation of MBR. The measure is that 1) the parameters of activated sludge concentration (X) and membrane flux should be lower than the critical values of X and membrane flux respectively, and 2) the activated sludge should be discharged periodically. The experimental results show that the combination backwashing of gas and perme- ated effluent is better than single gas backwashing or single permeated effluent backwashing. This technique can remove the cake layer deposited on the membrane surface, decrease the membrane fouling, and recover the membrane flux effectively. So it is effective for prevention of membrane fouling.展开更多
A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effecti...A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.展开更多
Seven schemes for the developing extension, four schemes for the mining of the whole field and five schemes for the parameter are put forward in this paper to rational choice of technical reform schemes of Mine No.1. ...Seven schemes for the developing extension, four schemes for the mining of the whole field and five schemes for the parameter are put forward in this paper to rational choice of technical reform schemes of Mine No.1. Pingdingshan Mining Bureau.On the basis of conventional technical analysis, an optimum economy-mathmetical model of the developing preparatory schemes is worked out and a synthetic optimum is carried out.展开更多
The basic principles of the Support Vector Machine (SVM) are introduced in this paper. A specific process to establish an SVM prediction model is given. To improve the precision of coal reserve estimation, a support v...The basic principles of the Support Vector Machine (SVM) are introduced in this paper. A specific process to establish an SVM prediction model is given. To improve the precision of coal reserve estimation, a support vector machine method, based on statistical learning theory, is put forward. The SVM model was trained and tested by using the existing exploration and exploitation data of Chencun mine of Yima bureau’s as the input data. Then coal reserves within a particular region were calculated. These calculated results and the actual results of the exploration block were compared. The maximum relative error was 10.85%, within the scope of acceptable error limits. The results show that the SVM coal reserve calculation method is reliable. This method is simple, practical and valuable.展开更多
The hydro-hammer sampler is a new type of sampler compared with traditional ones. An important part of this new offshore sampler is that the structure of the core cutter has a significant effect on penetration and cor...The hydro-hammer sampler is a new type of sampler compared with traditional ones. An important part of this new offshore sampler is that the structure of the core cutter has a significant effect on penetration and core recovery. In our experiments, a commercial finite element code with a capability of simulating large-strain frictional contact between two or more solid bodies is used to simulate the core cutter-soil interaction. The effects of the cutting edge shape, the diameter and the edge angle on penetration are analyzed by non-liner transient dynamic analysis using a finite element method （FEM）. Simulation results show that the cutter shape clearly has an effect on the penetration and core recovery. In addition, the penetration of the sampler increases with an increase in the inside diameter of the cutter, but decreases with an increase in the cutting angle. Based on these analyses, an optimum structure of the core cutter is designed and tested in the north margin of the Dalian gulf. Experiment results show that the penetration rate is about 16.5 m/h in silty clay and 15.4 m/h in cohesive clay, while the recovery is 68% and 83.3% resoectively.展开更多
Under the condition of weak anisotropy, the relation of P-wave anisotropy in direction to fractures of coal seams was researched in order to forecast the density and the direction of the fractures. Although the approx...Under the condition of weak anisotropy, the relation of P-wave anisotropy in direction to fractures of coal seams was researched in order to forecast the density and the direction of the fractures. Although the approximate solution by Rtiger is suitable for thick reservoirs, it has some limitations for the composite reflected wave from both roofs and floors of coal seams, as well as multiple reflections. So first, the phase velocity and group velocity as well as their travel time were calculated about the reflected P-wave of the coal seam. Then, the anisotropic coefficients of both roofs and floors were calculated by Rueger formulae and last, the section versus azimuth in fixed offset can be gotten by convolution. In addition, the relation of amplitude of the composite reflected wave to azimuth angle was discussed. The forward modelling results of the coal azimuth anisotropy show these： 1） the coal seam is the strong reflecting layer, but the change of the reflectivity caused by the azimuth anisotropy is smaller; 2） if the azimuth angle is parallel to the crack strike, the reflectivity reaches up to the maximum absolute value, however, if the azimuth angle is perpendicular to the crack strike, the absolute value of the reflection coefficient is minimum; and 3）the reflection coefficient is the cosine function of the azimuth angle and the period is π.展开更多
Patterns of ground movement and pore water pressure variation are obtained through a case study using a finite element method. With the progress of excavation, ground subsidence, ground inclination and horizontal disp...Patterns of ground movement and pore water pressure variation are obtained through a case study using a finite element method. With the progress of excavation, ground subsidence, ground inclination and horizontal displacement accelerates. Along the striking direction, a subsidence basin is formed on the ground surface induced by underground mining. The maximum subsidence is around 5.41m. The ratio of ground subsidence to the thickness of the coal seam is 1.08. The maximum inclination is 11.5 mm/m. The maximum horizontal displacement is 2.15 mm/m. At the time the coal has been excavated, the maximum pore water pressure reaches 25 kPa. In order to improve protection of structures lo- cated over the area with underground mining, the variation of additional stresses of a railway bridge induced by ground surface deformation is analyzed. The main effect of underground mining on the railway bridge is the tensile stress and the maximum value reaches as high as 4.29 MPa, which is greater than the concrete tensile strength.展开更多
In 3D urban visualization, large data volumes related to buildings are a major factor that limits the delivery and browsing speed in a web-based computer system. This paper proposes a new approach based on the level o...In 3D urban visualization, large data volumes related to buildings are a major factor that limits the delivery and browsing speed in a web-based computer system. This paper proposes a new approach based on the level of detail （LOD） technique advanced in 3D visualization in computer graphics. The key idea of LOD technique is to generalize details of object surfaces without losing details for delivery and displaying objects. This technique has been successfully used in visualizing one or a few multiple objects in films and other industries. However, applying the technique to 3D urban visualization requires an effective generalization method for urban buildings. Conventional two-dimensional （2D） generalization method at different scales provides a good generalization reference for 3D urban visualization, Yet, it is difficult to determine when and where to retrieve data for displaying buildings. To solve this problem, this paper defines an imaging scale point and image scale region for judging when and where to get the fight data for visualization. The results show that the average response time of view transformations is much decreased.展开更多
Problems in desulfurization of coal by electrochemical reduction is analyzed and calculated. The result shows that 1 ) the △rGm function of the reaction of pyrite into FeS and the modifying reaction decreasing the ox...Problems in desulfurization of coal by electrochemical reduction is analyzed and calculated. The result shows that 1 ) the △rGm function of the reaction of pyrite into FeS and the modifying reaction decreasing the oxygenous functions on coal surface is smaller than zero in a spontaneous reaction, and greater than zero in a non-spontaneous reaction; 2) the △rGm value can be adjusted by pH and the dosage of electrolyte to make it be greaterthan zero , which is favorable for the modifying reaction and useful for desulfurization of coal. The research has provided a theoretical foundation for determining reasonable technical parameters of desulfurization。展开更多
State-based models provide an attractive and simple approach to performance modeling. Unfortunately,this approach gives rise to two fundamental problems: 1) capturing the input loads to a system efficiently within suc...State-based models provide an attractive and simple approach to performance modeling. Unfortunately,this approach gives rise to two fundamental problems: 1) capturing the input loads to a system efficiently within such presentations; and 2) coping with the explosion in the number of states whtn system is compositionally presented. Both problems can be regarded as searching for some optimal representative state model with a minimal const. In this paper a probabilistic feedback search approach (popularly referred to as a genetic algorithm) was presented for locating good models with low (state) cost.展开更多
The thesis describes an advanced digital solution to mining digital image monitor system, which makes up the shortage of the traditional mining analog image monitor. It illustrates the system components and how to cho...The thesis describes an advanced digital solution to mining digital image monitor system, which makes up the shortage of the traditional mining analog image monitor. It illustrates the system components and how to choose the encoder bandwidth of the system. The problem of image multicast and its solution in LAN are also discussed.展开更多
The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the ...The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the conventionai types of mierostructure. The influence of the isothermal transformation temperatures on the mierostrueture and the mechanical properties of the steel bas been examined. Therefore, the strengthening meehanism of the new dual phase steel with ultra-high strength has been revealed.展开更多
The pyrolysis kinetics of three different kinds of fresh biomass (grass: triple A, wheat straw, corn straw) in nitrogen flow were studied by thermogravimetric analysis at five different heating rates. The kinetic para...The pyrolysis kinetics of three different kinds of fresh biomass (grass: triple A, wheat straw, corn straw) in nitrogen flow were studied by thermogravimetric analysis at five different heating rates. The kinetic parameters of the pyrolysis process were calculated using the method of Ozawa-Flynn-Wall and the mechanism of reactions were investi- gated using the method of Popescu. It was found that the values of activation energy varied in different temperature ranges. The pyrolysis processes are well described by the models of Zhuravlev (Zh) and valid for diffusion-controlled between 200 ℃ and 280 ℃, by Ginstling-Brounshtein (G-B), valid for diffusion-control between 280 ℃ and 310 ℃, for first-order chemical reaction between 310℃ and 350 ℃, by Zhuravlev (Zh) valid for diffusion-control between 350 ℃ and 430 ℃ and by the one-way transport model when temperatures are over 430 ℃.展开更多
Aimed at the lack of self-tuning PID parameters in conventional PID controllers, the structure and learning algorithm of an adaptive PID controller based on reinforcement learning were proposed. Actor-Critic learning ...Aimed at the lack of self-tuning PID parameters in conventional PID controllers, the structure and learning algorithm of an adaptive PID controller based on reinforcement learning were proposed. Actor-Critic learning was used to tune PID parameters in an adaptive way by taking advantage of the model-free and on-line learning properties of reinforcement learning effectively. In order to reduce the demand of storage space and to improve the learning efficiency, a single RBF neural network was used to approximate the policy function of Actor and the value function of Critic simultaneously. The inputs of RBF network are the system error, as well as the first and the second-order differences of error. The Actor can realize the mapping from the system state to PID parameters, while the Critic evaluates the outputs of the Actor and produces TD error. Based on TD error performance index and gradient descent method, the updating rules of RBF kernel function and network weights were given. Simulation results show that the proposed controller is efficient for complex nonlinear systems and it is perfectly adaptable and strongly robust, which is better than that of a conventional PID controller.展开更多
基金Projects 070414168 supported by the Provincial University National Natural Science Foundation of Anhui2006KJ009A by the Key National Science Foundation of Anhui Province
文摘Mining subsidence pools are water bodies formed by soil subsidence near mines. We studied the impact the surrounding coal production activities and power plants have on these waters by measuring the concentrations of harmful trace elements in these waters. The concentration of the four elements F, Hg, Se and As increased by 0.92%, 0.78%, 0.70% and 0.81%, respectively, in the Datong mining subsidence pool from November 2004 to November 2006. The four elements increased by 1.58%, 1.23%, 1.08% and 0.92%, respectively, in the Xie’er mining subsidence pool and 1.16%, 1.06%, 1.02% and 1.01%, respectively, in the Pansan mining subsidence pool over the same time period. The absolute levels of F, Hg, Se and As in the pool are related to the background levels of the elements. A close relationship between nearby coal mines and power plants and increasing levels of the measured elements is noted.
基金Project 20070411065 supported by the China Postdoctoral Science Foundation
文摘Wireless sensor networks (WSNs) are very important for monitoring underground mine safety. Sensor node deployment affects the performances of WSNs. In our study, a chain-type wireless underground mine sensor network (CWUMSN) is first pre- sented. A CWUMSN can monitor the environment and locate miners in underground mines. The lowest density deployment strate- gies of cluster head nodes are discussed theoretically. We prove that the lifetime of CWUMSN with a non-uniform deployment strategy is longer than with a uniform deployment strategy. Secondly, we present the algorithm of non-uniform lowest density de- ployment of cluster head nodes. Next, we propose a dynamic choice algorithm of cluster head nodes for CWUMSN which can im- prove the adaptability of networks. Our experiments of CWUMSN with both non-uniform lowest density and uniform lowest den- sity deployments are simulated. The results show that the lifetime of CWUMSN with non-uniform lowest density deployment is almost 2.5 times as long as that of the uniform lowest density deployment. This work provides a new deployment strategy for wire- less underground mine sensor networks and then effectively promotes the application of wireless sensor networks to underground mines.
基金Projects 2005CB221503 supported by the National Basic Research Program of China70533050 and 50674089 by the National Natural Science Foundation of China2005BA813B-3-06 by the National Tenth 5-Year Key Scientific and Technological Project
文摘When an extremely thick rock bed exists above a protected coal seam in the bending zone given the condition of a mining protective seam, this extremely thick rock bed controls the movement of the entire overlying stratum. This extremely thick rock bed, called a ＂main key stratum＂, will not subside nor break for a long time, causing lower fractures and bed separations not to close and gas can migrate to the bed separation areas along the fractures. These bed separations become gas enrichment areas. By analyzing the rule of fracture evolution and gas migration under the main key stratum after the deep protective coal seam has been mined, we propose a new gas drainage method which uses bore holes, drilled through rock and coal seams at great depths for draining pressure relief gas. In this method, the bores are located at a high level suction roadway （we can also drill them in the drilling field located high in an air gateway）. Given the practice in the Haizi mine, the gas drainage rate can reach 73% in the middie coal group, with a gas drainage radius over 100 m.
基金Projects BK2007145 supported by the Jiangsu Natural Science Foundation of China NCET-04-0454 by the Program for New Century Excellent Talentsin Universities
文摘In order to examine the factors which affect the range of heat transfer in earth surrounding subways, FLAC3D was adopted in this study to analyze these factors, under different conditions, in a systematic manner. When we compare these numerical tests, the results show that the main factors, affecting the heat transfer range are the thermal properties of the surrounding earth, the initial ground temperature and the temperature in the tunnel. The heat transfer coefficient between air and linings has little effect on the temperature distribution around the tunnel. The current results can provide a reference for improving the thermal environment in subways and optimizing the design of subwav ventilation and air conditioning.
基金Project 20050290010 supported by the Doctoral Foundation of Chinese Education Ministry
文摘It is very important to accurately recognize and locate pulverized and block coal seen in a coal mine's infrared image monitoring system. Infrared monitor images of pulverized and block coal were sampled in the roadway of a coal mine. Texture statistics from the grey level dependence matrix were selected as the criterion for classification. The distributions of the texture statistics were calculated and analysed. A normalizing function was added to the front end of the BP network with one hidden layer. An additional classification layer is joined behind the linear layer. The recognition of pulverized from block coal images was tested using the improved BP network. The results of the experiment show that texture variables from the grey level dependence matrix can act as recognizable features of the image. The innovative improved BP network can then recognize the pulverized and block coal images.
文摘The Wielandt-Hoffman theorem of the real symmetric matrix is extended into a plural matrix. On the basis of it, a similar theory about the trace of a matrix for the arithmetic mean, geometric mean inequality, Holder inequality and Minkowski inequality is proved.
文摘Membrane fouling is the main problem of membrane bioreactors (MBR), which seriously influ- ences its wastewater treatment effect and running. The characteristics of microbiology and hydrodynamics concerning membrane fouling were investigated and the measure was put forward for optimum operation of MBR. The measure is that 1) the parameters of activated sludge concentration (X) and membrane flux should be lower than the critical values of X and membrane flux respectively, and 2) the activated sludge should be discharged periodically. The experimental results show that the combination backwashing of gas and perme- ated effluent is better than single gas backwashing or single permeated effluent backwashing. This technique can remove the cake layer deposited on the membrane surface, decrease the membrane fouling, and recover the membrane flux effectively. So it is effective for prevention of membrane fouling.
文摘A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.
文摘Seven schemes for the developing extension, four schemes for the mining of the whole field and five schemes for the parameter are put forward in this paper to rational choice of technical reform schemes of Mine No.1. Pingdingshan Mining Bureau.On the basis of conventional technical analysis, an optimum economy-mathmetical model of the developing preparatory schemes is worked out and a synthetic optimum is carried out.
基金Project 072400430420 supported by the Natural Science Foundation of Henan Province
文摘The basic principles of the Support Vector Machine (SVM) are introduced in this paper. A specific process to establish an SVM prediction model is given. To improve the precision of coal reserve estimation, a support vector machine method, based on statistical learning theory, is put forward. The SVM model was trained and tested by using the existing exploration and exploitation data of Chencun mine of Yima bureau’s as the input data. Then coal reserves within a particular region were calculated. These calculated results and the actual results of the exploration block were compared. The maximum relative error was 10.85%, within the scope of acceptable error limits. The results show that the SVM coal reserve calculation method is reliable. This method is simple, practical and valuable.
基金Project 20002070005126 supported by the China Geological Survey
文摘The hydro-hammer sampler is a new type of sampler compared with traditional ones. An important part of this new offshore sampler is that the structure of the core cutter has a significant effect on penetration and core recovery. In our experiments, a commercial finite element code with a capability of simulating large-strain frictional contact between two or more solid bodies is used to simulate the core cutter-soil interaction. The effects of the cutting edge shape, the diameter and the edge angle on penetration are analyzed by non-liner transient dynamic analysis using a finite element method （FEM）. Simulation results show that the cutter shape clearly has an effect on the penetration and core recovery. In addition, the penetration of the sampler increases with an increase in the inside diameter of the cutter, but decreases with an increase in the cutting angle. Based on these analyses, an optimum structure of the core cutter is designed and tested in the north margin of the Dalian gulf. Experiment results show that the penetration rate is about 16.5 m/h in silty clay and 15.4 m/h in cohesive clay, while the recovery is 68% and 83.3% resoectively.
基金Projects 40574058 supported by National Natural Science Foundation of China and 2005cb221500 by the National Basic Research and Development (973)Program of China
文摘Under the condition of weak anisotropy, the relation of P-wave anisotropy in direction to fractures of coal seams was researched in order to forecast the density and the direction of the fractures. Although the approximate solution by Rtiger is suitable for thick reservoirs, it has some limitations for the composite reflected wave from both roofs and floors of coal seams, as well as multiple reflections. So first, the phase velocity and group velocity as well as their travel time were calculated about the reflected P-wave of the coal seam. Then, the anisotropic coefficients of both roofs and floors were calculated by Rueger formulae and last, the section versus azimuth in fixed offset can be gotten by convolution. In addition, the relation of amplitude of the composite reflected wave to azimuth angle was discussed. The forward modelling results of the coal azimuth anisotropy show these： 1） the coal seam is the strong reflecting layer, but the change of the reflectivity caused by the azimuth anisotropy is smaller; 2） if the azimuth angle is parallel to the crack strike, the reflectivity reaches up to the maximum absolute value, however, if the azimuth angle is perpendicular to the crack strike, the absolute value of the reflection coefficient is minimum; and 3）the reflection coefficient is the cosine function of the azimuth angle and the period is π.
基金Project 50574088 supported by the Nation Natural Science Foundation of China
文摘Patterns of ground movement and pore water pressure variation are obtained through a case study using a finite element method. With the progress of excavation, ground subsidence, ground inclination and horizontal displacement accelerates. Along the striking direction, a subsidence basin is formed on the ground surface induced by underground mining. The maximum subsidence is around 5.41m. The ratio of ground subsidence to the thickness of the coal seam is 1.08. The maximum inclination is 11.5 mm/m. The maximum horizontal displacement is 2.15 mm/m. At the time the coal has been excavated, the maximum pore water pressure reaches 25 kPa. In order to improve protection of structures lo- cated over the area with underground mining, the variation of additional stresses of a railway bridge induced by ground surface deformation is analyzed. The main effect of underground mining on the railway bridge is the tensile stress and the maximum value reaches as high as 4.29 MPa, which is greater than the concrete tensile strength.
基金Project 40471109 supported by the National Natural Science Foundation of China
文摘In 3D urban visualization, large data volumes related to buildings are a major factor that limits the delivery and browsing speed in a web-based computer system. This paper proposes a new approach based on the level of detail （LOD） technique advanced in 3D visualization in computer graphics. The key idea of LOD technique is to generalize details of object surfaces without losing details for delivery and displaying objects. This technique has been successfully used in visualizing one or a few multiple objects in films and other industries. However, applying the technique to 3D urban visualization requires an effective generalization method for urban buildings. Conventional two-dimensional （2D） generalization method at different scales provides a good generalization reference for 3D urban visualization, Yet, it is difficult to determine when and where to retrieve data for displaying buildings. To solve this problem, this paper defines an imaging scale point and image scale region for judging when and where to get the fight data for visualization. The results show that the average response time of view transformations is much decreased.
基金National Natural Science Foundation of China(50174054)
文摘Problems in desulfurization of coal by electrochemical reduction is analyzed and calculated. The result shows that 1 ) the △rGm function of the reaction of pyrite into FeS and the modifying reaction decreasing the oxygenous functions on coal surface is smaller than zero in a spontaneous reaction, and greater than zero in a non-spontaneous reaction; 2) the △rGm value can be adjusted by pH and the dosage of electrolyte to make it be greaterthan zero , which is favorable for the modifying reaction and useful for desulfurization of coal. The research has provided a theoretical foundation for determining reasonable technical parameters of desulfurization。
文摘State-based models provide an attractive and simple approach to performance modeling. Unfortunately,this approach gives rise to two fundamental problems: 1) capturing the input loads to a system efficiently within such presentations; and 2) coping with the explosion in the number of states whtn system is compositionally presented. Both problems can be regarded as searching for some optimal representative state model with a minimal const. In this paper a probabilistic feedback search approach (popularly referred to as a genetic algorithm) was presented for locating good models with low (state) cost.
文摘The thesis describes an advanced digital solution to mining digital image monitor system, which makes up the shortage of the traditional mining analog image monitor. It illustrates the system components and how to choose the encoder bandwidth of the system. The problem of image multicast and its solution in LAN are also discussed.
文摘The microstructure characteristies of the dual phase strueture of austenite and bamite obtained in a silicon high carbon low-alloy steel,isothermally transformed, have been inverstigated and compared witb that of the conventionai types of mierostructure. The influence of the isothermal transformation temperatures on the mierostrueture and the mechanical properties of the steel bas been examined. Therefore, the strengthening meehanism of the new dual phase steel with ultra-high strength has been revealed.
基金Project 50474056 supported by the National Natural Science Foundation of China
文摘The pyrolysis kinetics of three different kinds of fresh biomass (grass: triple A, wheat straw, corn straw) in nitrogen flow were studied by thermogravimetric analysis at five different heating rates. The kinetic parameters of the pyrolysis process were calculated using the method of Ozawa-Flynn-Wall and the mechanism of reactions were investi- gated using the method of Popescu. It was found that the values of activation energy varied in different temperature ranges. The pyrolysis processes are well described by the models of Zhuravlev (Zh) and valid for diffusion-controlled between 200 ℃ and 280 ℃, by Ginstling-Brounshtein (G-B), valid for diffusion-control between 280 ℃ and 310 ℃, for first-order chemical reaction between 310℃ and 350 ℃, by Zhuravlev (Zh) valid for diffusion-control between 350 ℃ and 430 ℃ and by the one-way transport model when temperatures are over 430 ℃.
基金Projects 0601033B supported by the Science Foundation for Post-doctoral Scientists of Jiangsu Province, 0C4466 and 0C060093the Scientific and Technological Foundation for Youth of China University of Mining & Technology
文摘Aimed at the lack of self-tuning PID parameters in conventional PID controllers, the structure and learning algorithm of an adaptive PID controller based on reinforcement learning were proposed. Actor-Critic learning was used to tune PID parameters in an adaptive way by taking advantage of the model-free and on-line learning properties of reinforcement learning effectively. In order to reduce the demand of storage space and to improve the learning efficiency, a single RBF neural network was used to approximate the policy function of Actor and the value function of Critic simultaneously. The inputs of RBF network are the system error, as well as the first and the second-order differences of error. The Actor can realize the mapping from the system state to PID parameters, while the Critic evaluates the outputs of the Actor and produces TD error. Based on TD error performance index and gradient descent method, the updating rules of RBF kernel function and network weights were given. Simulation results show that the proposed controller is efficient for complex nonlinear systems and it is perfectly adaptable and strongly robust, which is better than that of a conventional PID controller.
