A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations...A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations with working face advanc- ing was simulated by a new model.The results show that the maximum value of bed separations moved forward gradually along with the working face advancing;the maxi- mum value of bed separations is 0.31～0.50 times of mining thickness.The key strata have a great influence upon surface subsidence during the overburden movement process.The mechanics parameters of new experiment are fitted with results in fields perfectly.展开更多
Superconducting electrodynamic suspension (EDS) presents numerous advantages, including large suspension gaps, high lift-to-drag ratios, and lower requirements for track irregularities. Recent advancements in supercon...Superconducting electrodynamic suspension (EDS) presents numerous advantages, including large suspension gaps, high lift-to-drag ratios, and lower requirements for track irregularities. Recent advancements in superconducting materials have further enhanced the feasibility of this technology, and hence multiple research institutions are actively developing and improving this high-speed rail technology. Superconducting EDS achieves passive suspension and guidance by the interaction between ground null-flux coils and onboard superconducting magnets, forming an electromechanical coupled system. Thus, electromechanical coupling modeling and equivalent experimental methods are essential in evaluating and optimizing this system. This article reviews the research on dynamic characteristics analysis of superconducting EDS, focusing on modeling and experimental methods. Firstly, it revisits the development history of superconducting EDS and the new opportunities brought by advancements in superconducting materials. Secondly, it discusses various modeling approaches for the suspension system, emphasizing their benefits and limitations. Thirdly, it describes equivalent experimental methods and their respective application scenarios. Then, it reviews important conclusions and possible optimization methods related to dynamic performance and electromechanical coupling research. Additionally, the sliding window method is introduced to improve computational efficiency in vehicle dynamics modeling. This article provides insights into the current state and future directions of superconducting EDS research, serving as a valuable reference for researchers and engineers.展开更多
The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rh...The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rheological behaviour of the insulation material during extrusion.Considering the pre-cross-linking effect,this study investigates the influence of molecular structure on the extrusion temperature,viscosity and shear rate distribution of insulation materials through equivalence experiments and simulations.The results indicate that the maximum temperature of 143℃ occurs at the extrusion die land,where pressure and shear rate are highest.Furthermore,based on the optimised simulation model with experimental results,an empirical formula was established for predicting the maximum extrusion temperature of different insulation materials.This study reveals that although an increased terminal double-bond content in low-density polyethylene(LDPE)enhances the reactivity of insulation materials and reduces their shelf life,it also allows for a reduction in cross-linking agent content,thereby mitigating pre-cross-linking.Insulation materials with a higher long-chain branching degree and terminal double-bond content in LDPE,combined with a lower cross-linking agent content,are less susceptible to pre-cross-linking,which are more suitable for long-length submarine cables,whereas the reduced by-products also benefit the manufacture of DC cables;high-speed shear promotes the diffusion of the cross-linking agent dicumyl peroxide and enhances its interaction with the polyethylene chains.This research elucidates the influence of pre-cross-linking on the extrusion performance of insulation materials and develops an insulation material formulation more suitable for long-duration extrusion.展开更多
基金The National Natural Science Funds Committee(50174035)
文摘A new experiment was made on the developing of bed separations and mining subsidence from Tangshan T2192 working face by equivalent materials simulation.The overburden deformation and the developing of bed separations with working face advanc- ing was simulated by a new model.The results show that the maximum value of bed separations moved forward gradually along with the working face advancing;the maxi- mum value of bed separations is 0.31～0.50 times of mining thickness.The key strata have a great influence upon surface subsidence during the overburden movement process.The mechanics parameters of new experiment are fitted with results in fields perfectly.
基金China Postdoctoral Science Foundation(2024M752424)National Natural Science Foundation of China(52305133,52232013).
文摘Superconducting electrodynamic suspension (EDS) presents numerous advantages, including large suspension gaps, high lift-to-drag ratios, and lower requirements for track irregularities. Recent advancements in superconducting materials have further enhanced the feasibility of this technology, and hence multiple research institutions are actively developing and improving this high-speed rail technology. Superconducting EDS achieves passive suspension and guidance by the interaction between ground null-flux coils and onboard superconducting magnets, forming an electromechanical coupled system. Thus, electromechanical coupling modeling and equivalent experimental methods are essential in evaluating and optimizing this system. This article reviews the research on dynamic characteristics analysis of superconducting EDS, focusing on modeling and experimental methods. Firstly, it revisits the development history of superconducting EDS and the new opportunities brought by advancements in superconducting materials. Secondly, it discusses various modeling approaches for the suspension system, emphasizing their benefits and limitations. Thirdly, it describes equivalent experimental methods and their respective application scenarios. Then, it reviews important conclusions and possible optimization methods related to dynamic performance and electromechanical coupling research. Additionally, the sliding window method is introduced to improve computational efficiency in vehicle dynamics modeling. This article provides insights into the current state and future directions of superconducting EDS research, serving as a valuable reference for researchers and engineers.
基金supported by the Programme of Beijing Huairou Laboratory(Grant No.ZD2022003A).
文摘The rheological properties of cable insulation materials are critical to the long-term continuous extrusion performance of high-voltage cables,with the pre-cross-linking effect playing a key role in determining the rheological behaviour of the insulation material during extrusion.Considering the pre-cross-linking effect,this study investigates the influence of molecular structure on the extrusion temperature,viscosity and shear rate distribution of insulation materials through equivalence experiments and simulations.The results indicate that the maximum temperature of 143℃ occurs at the extrusion die land,where pressure and shear rate are highest.Furthermore,based on the optimised simulation model with experimental results,an empirical formula was established for predicting the maximum extrusion temperature of different insulation materials.This study reveals that although an increased terminal double-bond content in low-density polyethylene(LDPE)enhances the reactivity of insulation materials and reduces their shelf life,it also allows for a reduction in cross-linking agent content,thereby mitigating pre-cross-linking.Insulation materials with a higher long-chain branching degree and terminal double-bond content in LDPE,combined with a lower cross-linking agent content,are less susceptible to pre-cross-linking,which are more suitable for long-length submarine cables,whereas the reduced by-products also benefit the manufacture of DC cables;high-speed shear promotes the diffusion of the cross-linking agent dicumyl peroxide and enhances its interaction with the polyethylene chains.This research elucidates the influence of pre-cross-linking on the extrusion performance of insulation materials and develops an insulation material formulation more suitable for long-duration extrusion.
