The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel ...The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel geometry, which are generally not known in detail in priority. Hence, based on the field and laboratory data, various possible combinations should be analyzed to cater for the unforeseeable mining conditions. This paper discusses the use of numerical model for selecting an appropriate chock capacity based on the site-specific geological and geotechnical information and longwall panel geometry. The fracture mechanisms of immediate and main roofs are also discussed for various panel widths and support capacities. For the models considered, the chock convergence is predicted to increase by about 33% due to the increase in face width from 100 to 260 m. Similarly, the massive roof strata are found to yield higher chock convergence compared to bedded strata.展开更多
Ultraviolet(UV)radiation poses risks to both human health and organics.In response to the urgent demand for UV-shielding across various applications,extensive endeavors have been dedicated to developing UV-shielding m...Ultraviolet(UV)radiation poses risks to both human health and organics.In response to the urgent demand for UV-shielding across various applications,extensive endeavors have been dedicated to developing UV-shielding materials spanning from wide-bandgap semiconductors to organo-inorganic composite films.However,existing UV shielding materials,though suitable for daily use,cannot meet the demands of extreme conditions.In this work,we incorporated CeO_(2)as a UV absorber into Y_(2)O_(3)transparent ceramics for UV-shielding.The effect of CeO_(2)concentration on the optical,mechanical,and thermal properties of Y_(2)O_(3)ceramics was systematically investigated.These findings indicate that CeO_(2)serves not only as a UV absorber but also as an effective sintering aid for Y_(2)O_(3)transparent ceramics.The 5 at%Ce-doped Y_(2)O_(3)transparent ceramics exhibit the optimal optical quality,with in-line transmittance of~77%at 800 nm.The introduction of Ce shifted the UV cutoff edge of Y_(2)O_(3)transparent ceramics from 250 to 375 nm,which was attributed to the visible band absorption of Ce^(4+).This shift grants UV shielding capabilities to Y_(2)O_(3)transparent ceramics,resulting in 100%shielding for ultraviolet C(UVC,100-280 nm)and ultraviolet B(UVB,280-320 nm)and~95%shielding for ultraviolet A(UVA,320-400 nm).The service stability(optical properties)under various corrosive conditions(acid,alkali,UV irradiation,and high temperature)was investigated,confirming the excellent stability of this transparent ceramic UV-shielding material.A comparison of the performance parameters of transparent ceramics with those of traditional UV shielding materials such as glasses,films,and coatings was conducted.Our work provides innovative design concepts and an effective solution for UVshielding materials for extreme conditions.展开更多
文摘The selection of optimum chock (support) capacity is very crucial for a successful longwall mining. The selection of chock capacity depends on the site-specific geotechnical parameters, constraints and longwall panel geometry, which are generally not known in detail in priority. Hence, based on the field and laboratory data, various possible combinations should be analyzed to cater for the unforeseeable mining conditions. This paper discusses the use of numerical model for selecting an appropriate chock capacity based on the site-specific geological and geotechnical information and longwall panel geometry. The fracture mechanisms of immediate and main roofs are also discussed for various panel widths and support capacities. For the models considered, the chock convergence is predicted to increase by about 33% due to the increase in face width from 100 to 260 m. Similarly, the massive roof strata are found to yield higher chock convergence compared to bedded strata.
基金funded by the National Natural Science Foundation of China(Nos.U21A20441 and U22B2070).
文摘Ultraviolet(UV)radiation poses risks to both human health and organics.In response to the urgent demand for UV-shielding across various applications,extensive endeavors have been dedicated to developing UV-shielding materials spanning from wide-bandgap semiconductors to organo-inorganic composite films.However,existing UV shielding materials,though suitable for daily use,cannot meet the demands of extreme conditions.In this work,we incorporated CeO_(2)as a UV absorber into Y_(2)O_(3)transparent ceramics for UV-shielding.The effect of CeO_(2)concentration on the optical,mechanical,and thermal properties of Y_(2)O_(3)ceramics was systematically investigated.These findings indicate that CeO_(2)serves not only as a UV absorber but also as an effective sintering aid for Y_(2)O_(3)transparent ceramics.The 5 at%Ce-doped Y_(2)O_(3)transparent ceramics exhibit the optimal optical quality,with in-line transmittance of~77%at 800 nm.The introduction of Ce shifted the UV cutoff edge of Y_(2)O_(3)transparent ceramics from 250 to 375 nm,which was attributed to the visible band absorption of Ce^(4+).This shift grants UV shielding capabilities to Y_(2)O_(3)transparent ceramics,resulting in 100%shielding for ultraviolet C(UVC,100-280 nm)and ultraviolet B(UVB,280-320 nm)and~95%shielding for ultraviolet A(UVA,320-400 nm).The service stability(optical properties)under various corrosive conditions(acid,alkali,UV irradiation,and high temperature)was investigated,confirming the excellent stability of this transparent ceramic UV-shielding material.A comparison of the performance parameters of transparent ceramics with those of traditional UV shielding materials such as glasses,films,and coatings was conducted.Our work provides innovative design concepts and an effective solution for UVshielding materials for extreme conditions.
