A new method for calculating the permeability coefficient of coal seams

The permeability coefficient of coal seams is a key parameter that judges the difficulty of gas flow in coal seams. In the current calculation formula for the permeability coefficient of coal seams, the coefficient of the nonlinear partial differential equation with variable pressure is assumed to be a constant, which leads to significant errors in the theoretical derivation results and results in significant deviations in the permeability coefficient measured on site. To solve the inaccurate determination problem of the coal seam permeability coefficient, this paper derived the process of using the radial flow rate method to test the coal seam permeability coefficient, and pointed out the problems of this method during the derivation process. Based on the Langmuir's gas content and Darcy's law, a dimensionless model was established, and the model solution results were inverted and fitted. A new calculation formula for the coal seam permeability coefficient was obtained, which was verified by on-site drilling data. The current testing method for coal seam permeability coefficient was revised, and an accurate and reliable new method for calculating the coal seam permeability coefficient was proposed. The results indicate that using a parabolic equation to represent the coal seam gas content and treating variable p1.5 as a constant to derive the coal seam permeability coefficient calculation formula is equivalent to fitting the gas content into a proportional relationship with the square of pressure. There are theoretical problems and significant errors in actual calculations. Using the Langmuir dimensionless model to calculate Y' for inversion fitting can solve the shortcomings of current calculation methods. When the product of the adsorption constant b and the original gas pressure p0 (the dimensionless original gas pressure) is different, the function curve of the dimensionless gas emission velocity Y' and the dimensionless time Fo' is significantly different. Therefore, the permeability coefficient calculation formula containing the dimensionless original gas pressure was obtained. When the coal seam and drilling conditions are constant, the values of the coal seam permeability coefficient λ calculated from the gas emission volume at different times have a good reproducibility. The new on-site measurement method for the permeability coefficient of coal seams is completely the same as the current method without adding additional workload. However, the new calculating method is more accurate and reliable

Jørgensen’s Inequality and Algebraic Convergence Theorem in Quaternionic Hyperbolic Isometry Groups

We obtain an analogue of Jørgensen's inequality in quaternionic hyperbolic space. As an application, we prove that if the r-generator quaternionic Kleinian group satisfies I-condition, then its algebraic limit is also a quaternionic Kleinian group. Our results are generalizations of the counterparts in the n-dimensional real hyperbolic space

Flux regulation through glycolysis and respiration is balanced by inositol pyrophosphates in yeast

Although many prokaryotes have glycolysis alternatives, it\u27s considered as the only energy-generating glucose catabolic pathway in eukaryotes. Here, we managed to create a hybrid-glycolysis yeast. Subsequently, we identified an inositol pyrophosphatase encoded by OCA5 that could regulate glycolysis and respiration by adjusting 5-diphosphoinositol 1,2,3,4,6-pentakisphosphate (5-InsP7) levels. 5-InsP7 levels could regulate the expression of genes involved in glycolysis and respiration, representing a global mechanism that could sense ATP levels and regulate central carbon metabolism. The hybrid-glycolysis yeast did not produce ethanol during growth under excess glucose and could produce 2.68 g/L free fatty acids, which is the highest reported production in shake flask of Saccharomyces cerevisiae. This study demonstrated the significance of hybrid-glycolysis yeast and determined Oca5 as an inositol pyrophosphatase controlling the balance between glycolysis and respiration, which may shed light on the role of inositol pyrophosphates in regulating eukaryotic metabolism

Mining Safety of Longwall Top-coal Caving in China

Longwall top-coal caving technology has developed rapidly in China, in recent years. The application of longwall top-coal caving can double both the productivity and the efficiency of a working face and reduce the cost of production by 30 to 40%. Using standard longwall equipment, annual production can reach 3 million metric tons (Mt), and a maximum of 4.1 Mt has been obtained; many top-coal caving longwall working faces can obtain 200 tons per man-shift. Longwall top-coal caving is distinctly different from slice mining in thicken seam. Concerns of safety and productivity for this method have been raised in recent years. This paper will discuss the following: 1) how to recognize the law of firedamp emission, accumulation and outburst; 2) how to resolve the ventilation problem in a highly gassy working face; 3) how to recognize the law of spontaneous combustion of ignitable coal, and to avoid spontaneous combustion in gob area; and 4) How to control dust in longwall top-coal caving face

The Boundedness on Mixed Hardy Spaces

The boundedness of operators on Hardy spaces is usually given by atomic decomposition. In this paper, we obtain the boundedness of singular integral operators in mixed Journé class on mixed Hardy spaces by a direct method

Study on mathematical model of coal particles gas adsorption under different particle sizes and pressures

Gas adsorption experiment with coal particles is a basic means to study the gas flow mechanism of coal matrix. In order to explore the influence of coal particle shape on coal gas adsorption law, a constant temperature and pressure adsorption experiment was designed to obtain the adsorption characteristics of coal samples with four particle sizes under different gas pressures. Based on the gradient diffusion theory of free gas density in coal matrix, the mathematical models of constant pressure adsorption of cylindrical and spherical coal gas were established respectively, and solved by finite difference method, and the simulation results were verified by experimental data. It is found that the simulation results obtained by considering the coal particles as spherical or cylindrical have a good match with the experimental results, which proves the accuracy and reliability of the gradient diffusion theory of free gas density in coal matrix. The diffusion coefficient increases with the increase of coal particle size. The influence of gas adsorption pressure on the diffusion coefficient of micropore is small, and the diffusion coefficient of difference of surface area between the two shapes

A New Method of Boundary Treatment in Heat Conduction Problems with Finite Element Method

AbstractIn regards to the defect of respectively handling three conditions, this paper puts forward a new unified expression fitting for different boundary conditions. It also obtains the parameter values of expression in different boundary conditions. Take the infinite square cylinder putting into cold liquor as an example, it works out a program using the improved new boundary treatment to simulate cylinder temperature field. This paper gets distributions of temperature field at four different times. The results of simulation not only meet the physical situation, but also have high precision compared with the theoretical solutions. Since being easy to deal with complex boundary conditions, the new way makes the FEM useful again in engineering calculation and research

Numerical Simulation of Deformation and Failure Mechanism of Main Inclined Shaft in Yuxi Coal Mine, China

Disturbance stresses can cause deformation and damage to a tunnel’s rock, potentially threatening the mine’s safety. This paper investigates the effects of disturbance damage on the main inclined shaft due to the excavation of an electromechanical chamber in a deep inclined shaft at Yuxi Mine. Specifically, a numerical model was constructed using Midas GTX NX and Fast Lagrangian Analysis of Continua in Three Dimensions (FLAC3D) to match the actual engineering conditions, and to reveal the stresses and deformations in the surrounding rock of the main inclined shaft before and after the excavation of the main inclined shaft, the electromechanical chamber and the head chamber. The results revealed that the surrounding rock stress around the main inclined shaft is significantly influenced by excavation disturbance. The bottom bulge occurred due to the unstable vertical and shear stresses in the bottom coal bed moving into free space. After the excavation of the electromechanical chamber, the maximum displacement of the floor can be increased from 0.35468 m to 0.64301 m, nearly doubled, and a large area of surrounding rock deformation occurs in the inclined shaft falling roadway. Affected by excavation disturbance, the maximum deformation of floor can reach 1.06 m, with a wide fluctuation range. The main area of damage to the surrounding rock was identified, except for the main inclined shaft, which occurred near the intersection of the inclined shaft and the drop level location. This area is mainly affected by superimposed tensile stress damage, prone to large area floor heave and spalling. The research content is expected to provide certain theoretical support in taking measures to deal with the deformation and failure of the surrounding rock in a main inclined shaft

Dynamic Recrystallization Nucleation Mechanism and Precipitation Behavior of Homogeneous Al-Zn-Mg-Cu Alloy during Hot Deformation

The hot deformation behavior of Al-Zn-Mg-Cu alloy was investigated by flow stress curves in isothermal hot compression experiments with deformation temperatures of 350–450 °C and strain rates of 0.01 s−1 to 1 s−1, and the constitutive equation of homogeneous alloy was obtained. At the same time, the dynamic recrystallization and precipitation behavior during hot deformation and the relationship between them and the Z parameters were studied by using EBSD and TEM. DRV is the main mechanism of dynamic softening. With the decrease in Z parameter, the softening mechanism changes from dynamic recovery to discontinuous dynamic recrystallization or continuous dynamic recrystallization. At a higher Z parameter, the dislocation density and precipitated phase density are also higher because the high dislocation density provides heterogeneous nucleation sites of the precipitated phase. A large number of precipitates in the alloy also inhibit the nucleation and growth of dynamic recrystallization by hindering dislocation movement and grain boundary migration