Mechanical Properties of Rock–Coal–Rock Composites at Different Inclined Coal Seam Thicknesses

A comprehensive understanding of the mechanical properties of coal and rock sections is necessary for interpreting the deformation and failure modes of such underground sections and for evaluating the potential dynamic hazards. However, most studies have focused on horizontal coal–rock composites and the mechanical properties of inclined coal–rock composites have not been considered. To explore the influence of different confining pressures and inclined coal seam thicknesses on the mechanical properties and failure characteristics of rock–coal–rock (RCR) composites, a numerical model based on the particle flow code was used to perform simulations on five inclined RCR composites at different confining pressures. The results show that the mechanical properties and failure characteristics of the RCR composites are affected considerably by the inclined coal seam thickness and the confining pressure. (1) When the inclined coal seam thickness is constant, the elasticity modulus of the inclined RCR composite increases nonlinearly with the confining pressure at first, and then remains constant. At the same confining pressure, the elasticity modulus of the inclined RCR composite decreases nonlinearly with the inclined coal seam thickness. (2) When the confining pressure is constant, the peak stress of the inclined RCR composite decreases with the increase of the inclined coal seam thickness. When the inclined coal seam thickness is constant, the peak stress increases with the confining pressure. (3) As the inclined coal seam thickness increases, the peak strain of the inclined RCR composite first decreases rapidly, and then remains constant when there is no confining pressure. When the confining pressure is between 5 and 20 MPa, the peak strain of the inclined RCR composite gradually increases. (4) In the absence of confining pressure, there are few microcracks in the rock at an inclined coal seam thickness of 10 mm, whereas all the other cracks are in the coal section. When the confining pressure ranges between 5 and 20 MPa, the failure modes of the RCR composite can be divided into Y- and X-types.

Performance Analysis of Natural γ-Ray Coal Seam Thickness Sensor and Its Application in Automatic Adjustment of Shearer’s Arms

The technology of coal-rock interface recognition is the core of realizing the automatic heightening technology of shearer’s rocker. Only by accurately and quickly identifying the interface of coal and rock can we realize the fully automatic control of shearer. As the only one used in the actual detection of coal mining machine drum cutting coal seam after the thickness of the remaining coal seam detection method, natural γ-ray has a very practical advantage. Based on the relationship between the attenuation of the natural γ-ray passing through the coal seam and the thickness of the coal seam, the mathematical model of the attenuation of the natural γ-ray penetrating coal seam is established. By comparing the attenuation intensity of γ-ray with or without brackets, it is verified that the hydraulic girders will absorb some natural γ-rays. Finally, this paper uses the ground simulation experiment and the field experiment to verify the correctness of the mathematical model and finally develop the natural γ-ray seam thickness sensor. The sensor has the function of indicating the thickness of the coal seam, measuring the natural γ-ray intensity, and storing and processing the data.

Ultrasonic welding of polymer fi lms

The choice of the method of ultrasonic welding of polymer fi lms is substantiated, its advantages over other welding methods are noted.It is shown that the parameters determining the performance of seam ultrasonic welding process for polymer fi lms are the amplitude of the waveguide oscillations, the welding static pressure and the speed of welding with a fi xed gap on a rotating support roller with self-stabilization of the welding seam thickness.

Coal Seam Thickness Prediction Based on Transition Probability of Structural Elements

Coal seam thickness prediction is crucial in coal mine design and coal mining. In order to improve the prediction accuracy, an improved Kriging interpolation method on the basis of efficient data and Radial Basis Function (RBF-Kriging) is firstly proposed to interpolate the cutting data that is obtained in pre-mining, especially at the edge of the geological surface of coal seam by taking into account the spatial structure and the efficient spatial range, ensuring the integrity of the edge data during the movement of structural elements. Subsequently, a structural element transition probability based Gaussian process progression (STTP-GPR) method is proposed to predict the coal seam thickness from the interpolated coal seam data. The experimental results demonstrated that the proposed STTP-GPR method has superior performance in coal seam thickness prediction. The average absolute error of thickness prediction for thin coal seams is 0.025 m, which significantly improves the prediction accuracy in comparison to the existing back propagation (BP) neural networks, support vector machine, and Gaussian process regression methods.

Influence of seam types on seam quality of outdoor clothing

Purpose The purpose of this paper is to propose a rational and complete design scheme of seam type of outdoor clothing, so as to improve the seam efficiency and appearance of outdoor clothing, as well as to provide an optimal seam base for the subsequent pressure adhesive process. Design/methodology/approach Four types of common outdoor fabrics and four seam types were selected. Seam strength and thickness were measured. Seam efficiency and seam thickness strain were calculated to evaluate seam quality. Multiple linear regression analysis was adopted to analyze the influence of seam type essential factors on seam strength. Findings Among the component factors of seam type, based on two stitches, seam strength was significantly affected by stitch distance, followed by fabric layer on the seam side. The increase of stitch and the interaction among fabrics can effectively improve the seam efficiency. The methods are as follows: the increase of stitches, stitch distance shortening, the increase of fabric layers, etc. The change of seam type had no significant influence on seam thickness strain. A seam-type design scheme of outdoor clothing with good mechanical and appearance properties was designed by choosing the seam types FX1, FX2 and FX4. Originality/value This paper designed a practical scheme of seam-type design of outdoor clothing, which has been applied in the industrial production process. It is important for guiding the improvement of seam quality and the production efficiency of outdoor clothing.