为满足全球无缝覆盖、应急通信、物联网与航空海事等新兴业务需求,3GPP R19阶段对NTN进行了系统性增强。相比R18以透明转发为主的架构,3GPP R19 NR NTN首次引入星上再生处理架构,实现接入网与核心网功能在卫星上的灵活部署,显著降低端...为满足全球无缝覆盖、应急通信、物联网与航空海事等新兴业务需求,3GPP R19阶段对NTN进行了系统性增强。相比R18以透明转发为主的架构,3GPP R19 NR NTN首次引入星上再生处理架构,实现接入网与核心网功能在卫星上的灵活部署,显著降低端到端时延并提升系统容量,并对R18多个方面进行了增强和扩展,使得5G技术方案更加完整,技术能力进一步增强,为5G NR NTN商用提供了坚实的技术基础。以当前6G卫星互联网发展中面临的挑战作为出发点,重点围绕R19 NR NTN核心架构、空口与性能优化、移动性与服务连续性、终端与场景扩展等方面展开分析,最后对R20的技术发展进行了展望。展开更多
The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by ...The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.展开更多
This paper analyzes the oxidation law of metal particles and proposes a new oxidation reaction rate model,based on measurements of thermogravimetric-mass spectrometer(TG-MS),X-ray diffractometer(XRD)and scanning elect...This paper analyzes the oxidation law of metal particles and proposes a new oxidation reaction rate model,based on measurements of thermogravimetric-mass spectrometer(TG-MS),X-ray diffractometer(XRD)and scanning electron microscope(SEM).The model is named EBM(egg broken model)with a formula of exponential law.According to the model,the aluminum particles do not react in a spherical shape,but crack and the melted metal inside flows out to form a new nonspherical surface and the reaction rate is still determined by the surface area.The model is verified with heating rates of 5℃/min,10℃/min and 25℃/min,and with particle size of 1–2μm,8–9μm and 20–22μm.Many models are based on spherical hypothesis and the new model gives a different physical illustration to explain oxidation progress of metal particles.The new model gives an exponential law,which fits the experimental data well,and it may be useful to understand oxidation mechanism of metal particles.展开更多
文摘为满足全球无缝覆盖、应急通信、物联网与航空海事等新兴业务需求,3GPP R19阶段对NTN进行了系统性增强。相比R18以透明转发为主的架构,3GPP R19 NR NTN首次引入星上再生处理架构,实现接入网与核心网功能在卫星上的灵活部署,显著降低端到端时延并提升系统容量,并对R18多个方面进行了增强和扩展,使得5G技术方案更加完整,技术能力进一步增强,为5G NR NTN商用提供了坚实的技术基础。以当前6G卫星互联网发展中面临的挑战作为出发点,重点围绕R19 NR NTN核心架构、空口与性能优化、移动性与服务连续性、终端与场景扩展等方面展开分析,最后对R20的技术发展进行了展望。
基金supported by the National Natural Science Foundation of China (Grant No. 11072238)the 111 Project of China (Grant No. B07-033)
文摘The convection in an annular container with heated bottom,cooled top and insulated side walls are studied by both linear instability analysis and direct numerical simulation.The onset of convection is investigated by linear stability analysis and corresponding pattern selection mechanisms are discussed.The nonlinear evolution of different flow patterns and the convective heat transfer are simulated.The transition to oscillatory flow is also given by stability analysis where the base flow is a steady three dimensional flow.The stability predictions are in good agreement with the numerical simulations,including both the growth rate and the dimensionless frequency.
基金financially supported by the joint fund of National Natural Science Foundation and China Academy of Engineering Physics(NSAF)under grant No.U1530157。
文摘This paper analyzes the oxidation law of metal particles and proposes a new oxidation reaction rate model,based on measurements of thermogravimetric-mass spectrometer(TG-MS),X-ray diffractometer(XRD)and scanning electron microscope(SEM).The model is named EBM(egg broken model)with a formula of exponential law.According to the model,the aluminum particles do not react in a spherical shape,but crack and the melted metal inside flows out to form a new nonspherical surface and the reaction rate is still determined by the surface area.The model is verified with heating rates of 5℃/min,10℃/min and 25℃/min,and with particle size of 1–2μm,8–9μm and 20–22μm.Many models are based on spherical hypothesis and the new model gives a different physical illustration to explain oxidation progress of metal particles.The new model gives an exponential law,which fits the experimental data well,and it may be useful to understand oxidation mechanism of metal particles.
