The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coe...The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coefficients in the simple airways have good agreement with the equation proposed by Taylor.However,for complex airways in operat- ing mines,the evaluated effective diffusion coefficients in the mines show higher values than that calculated by the Taylor's equation.A numerical simulation model using with movements of discrete particles dosed into ventilation flows has been developed to simu- late diffusion phenomena of gas or dust in mine airways.Numerical simulations had been conducted on distribution of tracers in single airways with ordinary profiles of mean velocity velocity fluctuations and Reynolds stress.As one of results,long band of diffused particles is obtained at the single airway of 600 m in length,and large effective diffusion coefficient is evaluated as 20 m^2/s.展开更多
This paper propoes the water level measuring method based on the image, while the ruler used to indicate the water level is stained. The contamination of the ruler weakens or eliminates many features which are require...This paper propoes the water level measuring method based on the image, while the ruler used to indicate the water level is stained. The contamination of the ruler weakens or eliminates many features which are required for the image processing. However, the feature of the color difference between the ruler and the water surface are firmer on the environmental change compare to the other features. As the color differeaces are embossed, only the region of the ruler is limited to eliminate the noise, and the average image is produced by using several continuous frames. A histogram is then produced on the height axis of the produced intensity average image. Local peaks and local valleys are detected, and the section between the peak and valley which have the greatest change is looked for. The valley point at this very moment is used to detect the water level. The detected water level is then converted to the actual water level by using the mapping table. The proposed method is compared to the ultrasonic based method to evaluate its accuracy and efficiency on the various contaminated environments.展开更多
If a geocentric 3D coordinate system is adopted in China to replace 2D non-geocentric coordinate system, the coordinates of the surface points will be changed accordingly. The influences on the current maps of China, ...If a geocentric 3D coordinate system is adopted in China to replace 2D non-geocentric coordinate system, the coordinates of the surface points will be changed accordingly. The influences on the current maps of China, especially the topographic maps, are discussed due to the replacement of the coordinate systems. Taking the replacement of Xi’an 80 coordinate system by GRS80 for a numerical example, this paper analyzes the changes of latitude, longitude, Gauss plane coordinates of the surface points, as well as the orientation and the length changes between the points on the map, including the changes of map border lines and sheet corner points.展开更多
基金the National Natural Science Foundation of China(50375026)
文摘The effective diffusion coefficients in mine ventilation-flows had been obtained as 4 to 200 m^2/s by matching the measured concentration-time curves with the advec- tion-diffusion equation.The turbulent diffusion coefficients in the simple airways have good agreement with the equation proposed by Taylor.However,for complex airways in operat- ing mines,the evaluated effective diffusion coefficients in the mines show higher values than that calculated by the Taylor's equation.A numerical simulation model using with movements of discrete particles dosed into ventilation flows has been developed to simu- late diffusion phenomena of gas or dust in mine airways.Numerical simulations had been conducted on distribution of tracers in single airways with ordinary profiles of mean velocity velocity fluctuations and Reynolds stress.As one of results,long band of diffused particles is obtained at the single airway of 600 m in length,and large effective diffusion coefficient is evaluated as 20 m^2/s.
基金supported by the Brain Korea 21 Project in 2010,the MKE(The Ministry of Knowledge Economy,Korea)the ITRC(Information Technology Research Center)support program(NIPA-2010-(C1090-1021-0010))
文摘This paper propoes the water level measuring method based on the image, while the ruler used to indicate the water level is stained. The contamination of the ruler weakens or eliminates many features which are required for the image processing. However, the feature of the color difference between the ruler and the water surface are firmer on the environmental change compare to the other features. As the color differeaces are embossed, only the region of the ruler is limited to eliminate the noise, and the average image is produced by using several continuous frames. A histogram is then produced on the height axis of the produced intensity average image. Local peaks and local valleys are detected, and the section between the peak and valley which have the greatest change is looked for. The valley point at this very moment is used to detect the water level. The detected water level is then converted to the actual water level by using the mapping table. The proposed method is compared to the ultrasonic based method to evaluate its accuracy and efficiency on the various contaminated environments.
文摘If a geocentric 3D coordinate system is adopted in China to replace 2D non-geocentric coordinate system, the coordinates of the surface points will be changed accordingly. The influences on the current maps of China, especially the topographic maps, are discussed due to the replacement of the coordinate systems. Taking the replacement of Xi’an 80 coordinate system by GRS80 for a numerical example, this paper analyzes the changes of latitude, longitude, Gauss plane coordinates of the surface points, as well as the orientation and the length changes between the points on the map, including the changes of map border lines and sheet corner points.
