Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-c...Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-coal drawing test with shields and the controlled test without shields are performed in the condition without any boundary effect. Test results show that shields will cause reduction in drawing volume of coal in the LTCC mining. The deflection phenomenon of drawing body is also observed in the controlled test, which is verified that the deflection of drawing body is caused by shield. It is found that the deflection angle decreases with increasing caving height, with the maximum value of atailand the minimum value of 0. In addition, the formula to calculate the drawing volume is proposed subsequently.The deflection of drawing body is numerically simulated using particle flow code PFC3 Dand the proposed formula to calculate drawing volume in LTCC is also verified.展开更多
The development of self-powered water purification technologies for decentralized applications is crucial for ensuring the provision of drinking water in resource-limited regions. The elimination of the dependence on ...The development of self-powered water purification technologies for decentralized applications is crucial for ensuring the provision of drinking water in resource-limited regions. The elimination of the dependence on external energy inputs and the attainment of self-powered status significantly expands the applicability of the treatment system in real-world scenarios. Hybrid energy harvesters, which convert multiple ambient energies simultaneously, show the potential to drive self-powered water purification facilities under fluctuating actual conditions. Here, we propose recent advancements in hybrid energy systems that simultaneously harvest various ambient energies (e.g., photo irradiation, flow kinetic, thermal, and vibration) to drive water purification processes. The mechanisms of various energy harvesters and point-of-use water purification treatments are first outlined. Then we summarize the hybrid energy harvesters that can drive water purification treatment. These hybrid energy harvesters are based on the mechanisms of mechanical and photovoltaic, mechanical and thermal, and thermal and photovoltaic effects. This review provides a comprehensive understanding of the potential for advancing beyond the current state-of-the-art of hybrid energy harvester-driven water treatment processes. Future endeavors should focus on improving catalyst efficiency and developing sustainable hybrid energy harvesters to drive self-powered treatments under unstable conditions (e.g., fluctuating temperatures and humidity).展开更多
This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the ...This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the brief history and basic procedures of LTCC.The framework of research on the drawing mechanism,basic concepts,and some theoretical models of LTCC are detailed in sect.research framework of top coal drawingmechanism.The authors note that theTop coal drawbody(TCD),Top coal boundary(TCB)and Top coal recovery ratio(TCRR)are key factors in the drawingmechanism.TheBody-boundary-ratio(BBR)research system has been the classic framework for research over the last 20 years.The modified Bergmark-Roos model,which considers the effects of the supporting rear canopy,flowing velocity of top coal,and its shape factor,is optimal for characterizing the TCD.A 3Dmodel to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed.In sect.physical testing and numerical simulation,the physical tests and numerical simulations in the literature are classified for ease of bibliographical review,and classic conclusions regarding the drawing mechanism of top coal are presented and discussedwith elaborate illustrations and descriptions.The deflection of the TCDis noted,and is caused by the shape of the rear canopy.The inclined coal seam always induces a largerTCD,and a deflection in theTCDhas also been observed in it.The effects of the drawing sequence and drawing interval on the TCRR are reviewed,where a long drawing interval is found to lead to significant loss of top coal.Its flowing behavior and velocity distribution are also presented.Sect.practical applications of drawingmechanisms forLTCCmines 4 summarizes over 10 cases where the TCRRof LTCCmines improved due to the guidance of the drawing mechanism.The final section provides a summary of the work here and some open questions.Prospective investigations are highlighted to give researchers guidance on promising issues in future research on L展开更多
基金financially supported by the Coal Joint Funds of the National Natural Science Foundation of China(No.U1361209)the National Basic Research Program of China(973 Program)(No.2013CB227903)
文摘Based on the loose medium flow field theory, the loose top-coal drawing law of longwall top-coal caving（LTCC） mining technology is studied by using self-developed three-dimensional（3D） test device. The loose top-coal drawing test with shields and the controlled test without shields are performed in the condition without any boundary effect. Test results show that shields will cause reduction in drawing volume of coal in the LTCC mining. The deflection phenomenon of drawing body is also observed in the controlled test, which is verified that the deflection of drawing body is caused by shield. It is found that the deflection angle decreases with increasing caving height, with the maximum value of atailand the minimum value of 0. In addition, the formula to calculate the drawing volume is proposed subsequently.The deflection of drawing body is numerically simulated using particle flow code PFC3 Dand the proposed formula to calculate drawing volume in LTCC is also verified.
基金supported by the National Key R&D Program of China(No.2022YFC3205400)the National Natural Science Foundation of China(Grant No.52200079).
文摘The development of self-powered water purification technologies for decentralized applications is crucial for ensuring the provision of drinking water in resource-limited regions. The elimination of the dependence on external energy inputs and the attainment of self-powered status significantly expands the applicability of the treatment system in real-world scenarios. Hybrid energy harvesters, which convert multiple ambient energies simultaneously, show the potential to drive self-powered water purification facilities under fluctuating actual conditions. Here, we propose recent advancements in hybrid energy systems that simultaneously harvest various ambient energies (e.g., photo irradiation, flow kinetic, thermal, and vibration) to drive water purification processes. The mechanisms of various energy harvesters and point-of-use water purification treatments are first outlined. Then we summarize the hybrid energy harvesters that can drive water purification treatment. These hybrid energy harvesters are based on the mechanisms of mechanical and photovoltaic, mechanical and thermal, and thermal and photovoltaic effects. This review provides a comprehensive understanding of the potential for advancing beyond the current state-of-the-art of hybrid energy harvester-driven water treatment processes. Future endeavors should focus on improving catalyst efficiency and developing sustainable hybrid energy harvesters to drive self-powered treatments under unstable conditions (e.g., fluctuating temperatures and humidity).
基金This work is funded by the National Natural Science Foundation of China(Grant No.51934008,51674264 to Jiachen Wang,Grant No.51974320 to Shengli Yang)Fundamental Research Funds for the Central Universities(Grant No.06500182 to Zhengyang Song)Funds from State Key Laboratory of Coal Resources in Western China(SKLCRKF20-07 to Zhengyang Song).
文摘This review details the state of the art in research on top coal drawing mechanisms in Longwall top coal caving(LTCC)by examining the relevant literature over the last two decades.It startswith an introduction of the brief history and basic procedures of LTCC.The framework of research on the drawing mechanism,basic concepts,and some theoretical models of LTCC are detailed in sect.research framework of top coal drawingmechanism.The authors note that theTop coal drawbody(TCD),Top coal boundary(TCB)and Top coal recovery ratio(TCRR)are key factors in the drawingmechanism.TheBody-boundary-ratio(BBR)research system has been the classic framework for research over the last 20 years.The modified Bergmark-Roos model,which considers the effects of the supporting rear canopy,flowing velocity of top coal,and its shape factor,is optimal for characterizing the TCD.A 3Dmodel to describe the TCB that considers the thicknesses of the coal seam and roof strata is reviewed.In sect.physical testing and numerical simulation,the physical tests and numerical simulations in the literature are classified for ease of bibliographical review,and classic conclusions regarding the drawing mechanism of top coal are presented and discussedwith elaborate illustrations and descriptions.The deflection of the TCDis noted,and is caused by the shape of the rear canopy.The inclined coal seam always induces a largerTCD,and a deflection in theTCDhas also been observed in it.The effects of the drawing sequence and drawing interval on the TCRR are reviewed,where a long drawing interval is found to lead to significant loss of top coal.Its flowing behavior and velocity distribution are also presented.Sect.practical applications of drawingmechanisms forLTCCmines 4 summarizes over 10 cases where the TCRRof LTCCmines improved due to the guidance of the drawing mechanism.The final section provides a summary of the work here and some open questions.Prospective investigations are highlighted to give researchers guidance on promising issues in future research on L
