The long-lasting expectation“the hotter the engine,the better”calls for the development of high-temperature metallic alloys.Although the high specific strengths of titanium alloys are compelling for such application...The long-lasting expectation“the hotter the engine,the better”calls for the development of high-temperature metallic alloys.Although the high specific strengths of titanium alloys are compelling for such applications,their deleterious softening beyond 600℃ imposes serious limitations.Much has been known for decades regarding the phase metallurgy for precipitation strengthening design in titanium alloys,however,the other facile strength promotion mechanism,dispersion strengthening,remains comparatively less-explored and unutilized.The present research concerns the multi-scale dispersion strengthening in titanium alloys,with mechanistic emphases on the critical plasticity micro-events that affect strength preservation.Due to the simultaneous introduction of intragranular dispersoids and intergranular reinforcers,the current titanium alloys present superior engineering tensile strength of 519 MPa at 700℃.Throughout the examined 25-800℃ temperature range,noticeable softening induced by the thermal activation occurs above 600℃,accompanied by evident strength loss.The temperature-dependence transition of dominated softening mechanisms from dynamic recovery to dynamic recrystallization has been clarified by theoretical calculations.Furthermore,the strengthening effect of multi-scale architectures is underpinned as the enhanced dislocation strengthening owing to the introduction of thermally-stable heterointerfaces,which could generically guide the design of similar heat-resistant titanium alloys.展开更多
Under the background of the rapid development of ground mobile communication,the advantages of high coverage,survivability,and flexibility of satellite communication provide air support to the construction of space in...Under the background of the rapid development of ground mobile communication,the advantages of high coverage,survivability,and flexibility of satellite communication provide air support to the construction of space information network.According to the requirements of the future space information communication,a software-defined Space-Air-Ground Integrated network architecture was proposed.It consisted of layered structure satellite backbone network,deep space communication network,the stratosphere communication network and the ground network.The Space-Air-Ground Integrated network was supported by the satellite backbone network.It provided data relay for the missions such as deep space exploration and controlled the deep-space spacecraft when needed.In addition,it safeguarded the anti-destructibility of stratospheric communication and assisted the stratosphere to supplement ground network communication.In this paper,algorithm requirements of the congestion control and routing of satellite backbone protocols for heterogeneous users’services were proposed.The algorithm requirements of distinguishing different service objects for the deep space communication and stratospheric communication network protocols were described.Considering the realistic demand for the dynamic coverage of the satellite backbone network and node cost,the multi-layer satellite backbone network architecture was constructed.On this basis,the proposed Software-defined Space-Air-Ground Integrated network architecture could be built as a large,scalable and efficient communication network that could be integrated into space,air,and ground.展开更多
A configurable U-Net architecture is trained to solve the multi-scale elliptical partial differential equations.The motivation is to improve the computational cost of the numerical solution of Navier-Stokes equations...A configurable U-Net architecture is trained to solve the multi-scale elliptical partial differential equations.The motivation is to improve the computational cost of the numerical solution of Navier-Stokes equations–the governing equations for fluid dynamics.Building on the underlying concept of V-Cycle multigrid methods,a neural network framework using U-Net architecture is optimized to solve the Poisson equation and Helmholtz equations–the characteristic form of the discretized Navier-Stokes equations.The results demonstrate the optimized U-Net captures the high dimensional mathematical features of the elliptical operator and with a better convergence than the multigrid method.The optimal performance between the errors and the FLOPS is the(3,2,5)case with 3 stacks of UNets,with 2 initial features,5 depth layers and with ELU activation.Further,by training the network with the multi-scale synthetic data the finer features of the physical system are captured.展开更多
天地一体化信息网络(space-ground integrated information network,SGIIN)作为未来信息获取、分发、传输和应用的核心基础设施,将对国民经济和社会发展起到非常大的作用。一体化网络的运行环境复杂和应用多样性,对一体化网络的网络架...天地一体化信息网络(space-ground integrated information network,SGIIN)作为未来信息获取、分发、传输和应用的核心基础设施,将对国民经济和社会发展起到非常大的作用。一体化网络的运行环境复杂和应用多样性,对一体化网络的网络架构和协议体系提出了重大挑战。在分析天地一体化网络特点的基础上,提出了两级组网体系,将一体化网络分为一级骨干网和二级接入网,给出了相应的体系架构。比较了不同的传输协议在空间环境下(如长时延、链路误码率高等特点)的性能,给出了量化分析结果;其次,在高度相同的卫星网络场景下,按照卫星网络传输任务的特点,分别从数据包转发、系统复杂度以及可移植性3个方面对不同的卫星网络路由算法进行性能分析。仿真和分析结果表明,基于CCSDS(consultative committee for space data systems)的协议体系可以作为未来天地一体化网络骨干网络的协议体系。展开更多
Railway power system is an inseparable part of the power system,therefore,the intelligent architecture of the railway power system should also be focused on.The unique power supply characteristics of the railway power...Railway power system is an inseparable part of the power system,therefore,the intelligent architecture of the railway power system should also be focused on.The unique power supply characteristics of the railway power system are analyzed and integrated railway smart grid architecture based on energy routers is proposed.Importantly,three corresponding resilient mode control methods are suggested for the proposed architecture.In the fourth section,a simulation model corresponding to the resilient control mode is built and the simulation results prove the feasibility of the proposed control mode.Equally,for the novel network-connected backbone router(NCBR),a 1000 kVA,27.5/10 kV NCBR engineering prototype is used to prove its effectiveness in practical applications.Finally,a differentiation analysis is given,followed by conclusions regarding the traditional power system and proposed system.展开更多
基金financially supported by the National Key R&D Program of China(No.2021YFB3701203)the National Natural Science Foundation of China(Nos.U22A20113,52261135543,52171137 and 52071116)the Heilongjiang Touyan Team Program,Heilongjiang Provincial Natural Science Foundation of China(No.TD2020E001).
文摘The long-lasting expectation“the hotter the engine,the better”calls for the development of high-temperature metallic alloys.Although the high specific strengths of titanium alloys are compelling for such applications,their deleterious softening beyond 600℃ imposes serious limitations.Much has been known for decades regarding the phase metallurgy for precipitation strengthening design in titanium alloys,however,the other facile strength promotion mechanism,dispersion strengthening,remains comparatively less-explored and unutilized.The present research concerns the multi-scale dispersion strengthening in titanium alloys,with mechanistic emphases on the critical plasticity micro-events that affect strength preservation.Due to the simultaneous introduction of intragranular dispersoids and intergranular reinforcers,the current titanium alloys present superior engineering tensile strength of 519 MPa at 700℃.Throughout the examined 25-800℃ temperature range,noticeable softening induced by the thermal activation occurs above 600℃,accompanied by evident strength loss.The temperature-dependence transition of dominated softening mechanisms from dynamic recovery to dynamic recrystallization has been clarified by theoretical calculations.Furthermore,the strengthening effect of multi-scale architectures is underpinned as the enhanced dislocation strengthening owing to the introduction of thermally-stable heterointerfaces,which could generically guide the design of similar heat-resistant titanium alloys.
基金This work is supported by Fundamental Research Funds for the Central Universities of China(328201911)C.G.(Chao Guo),the Open Project Program of National Engineering Laboratory for Agri-product Quality Traceability,C.G.(Chao Guo)+2 种基金Beijing Technology and Business University(BTBU)No.AQT-2018Y-B4,C.G.(Chao Guo)Higher Education Department of the Ministry of Education Industry-university Cooperative Education Project,C.G.(Chao Guo)Education and Teaching Reform Project of Beijing Electronic and Technology Institute,C.G.(Chao Guo).
文摘Under the background of the rapid development of ground mobile communication,the advantages of high coverage,survivability,and flexibility of satellite communication provide air support to the construction of space information network.According to the requirements of the future space information communication,a software-defined Space-Air-Ground Integrated network architecture was proposed.It consisted of layered structure satellite backbone network,deep space communication network,the stratosphere communication network and the ground network.The Space-Air-Ground Integrated network was supported by the satellite backbone network.It provided data relay for the missions such as deep space exploration and controlled the deep-space spacecraft when needed.In addition,it safeguarded the anti-destructibility of stratospheric communication and assisted the stratosphere to supplement ground network communication.In this paper,algorithm requirements of the congestion control and routing of satellite backbone protocols for heterogeneous users’services were proposed.The algorithm requirements of distinguishing different service objects for the deep space communication and stratospheric communication network protocols were described.Considering the realistic demand for the dynamic coverage of the satellite backbone network and node cost,the multi-layer satellite backbone network architecture was constructed.On this basis,the proposed Software-defined Space-Air-Ground Integrated network architecture could be built as a large,scalable and efficient communication network that could be integrated into space,air,and ground.
文摘A configurable U-Net architecture is trained to solve the multi-scale elliptical partial differential equations.The motivation is to improve the computational cost of the numerical solution of Navier-Stokes equations–the governing equations for fluid dynamics.Building on the underlying concept of V-Cycle multigrid methods,a neural network framework using U-Net architecture is optimized to solve the Poisson equation and Helmholtz equations–the characteristic form of the discretized Navier-Stokes equations.The results demonstrate the optimized U-Net captures the high dimensional mathematical features of the elliptical operator and with a better convergence than the multigrid method.The optimal performance between the errors and the FLOPS is the(3,2,5)case with 3 stacks of UNets,with 2 initial features,5 depth layers and with ELU activation.Further,by training the network with the multi-scale synthetic data the finer features of the physical system are captured.
文摘天地一体化信息网络(space-ground integrated information network,SGIIN)作为未来信息获取、分发、传输和应用的核心基础设施,将对国民经济和社会发展起到非常大的作用。一体化网络的运行环境复杂和应用多样性,对一体化网络的网络架构和协议体系提出了重大挑战。在分析天地一体化网络特点的基础上,提出了两级组网体系,将一体化网络分为一级骨干网和二级接入网,给出了相应的体系架构。比较了不同的传输协议在空间环境下(如长时延、链路误码率高等特点)的性能,给出了量化分析结果;其次,在高度相同的卫星网络场景下,按照卫星网络传输任务的特点,分别从数据包转发、系统复杂度以及可移植性3个方面对不同的卫星网络路由算法进行性能分析。仿真和分析结果表明,基于CCSDS(consultative committee for space data systems)的协议体系可以作为未来天地一体化网络骨干网络的协议体系。
基金Supported by the Zhuhai City Industry-University-Research Project(ZH22017001200019PWC).
文摘Railway power system is an inseparable part of the power system,therefore,the intelligent architecture of the railway power system should also be focused on.The unique power supply characteristics of the railway power system are analyzed and integrated railway smart grid architecture based on energy routers is proposed.Importantly,three corresponding resilient mode control methods are suggested for the proposed architecture.In the fourth section,a simulation model corresponding to the resilient control mode is built and the simulation results prove the feasibility of the proposed control mode.Equally,for the novel network-connected backbone router(NCBR),a 1000 kVA,27.5/10 kV NCBR engineering prototype is used to prove its effectiveness in practical applications.Finally,a differentiation analysis is given,followed by conclusions regarding the traditional power system and proposed system.
