在阵元数目一定的情况下,为了扩大阵列的孔径,本文采用非均匀稀疏对称阵列,其阵元间距不受四分之一载波波长的限制.为了避免由此带来的角度模糊问题和复杂的二维搜索,本文基于降秩思想,提出了近场源波达方向(DOA,Direction Of Arrival)...在阵元数目一定的情况下,为了扩大阵列的孔径,本文采用非均匀稀疏对称阵列,其阵元间距不受四分之一载波波长的限制.为了避免由此带来的角度模糊问题和复杂的二维搜索,本文基于降秩思想,提出了近场源波达方向(DOA,Direction Of Arrival)和距离的无模糊估计方法并且分析了角度估计的模糊性.此方法利用二阶统计量,只需进行一维搜索,且参数自动配对.因此,计算量大大地减少,且在阵元个数有限的情况下,大大地提高了空间分辨率.计算机仿真结果证实了此方法的有效性.展开更多
Land transport can no longer meet the requirements.European transport can be described by these words−crowded motorways and cities,dangerous emissions,ubiquitous traffic accidents,delays,expensive railways.Solutions a...Land transport can no longer meet the requirements.European transport can be described by these words−crowded motorways and cities,dangerous emissions,ubiquitous traffic accidents,delays,expensive railways.Solutions are being sought to transfer a large part of passengers and especially freight transport to(high-speed)rail,and efforts are moving towards electromobility,car-sharing,5G-connectivity,autonomous driving,MaaS(Mobility as a Service)-coordinated transport or hyperloop-type solutions.However,all these solutions have additional challenges and limitations.Solutions are not being searched where they really exist-in the mutual adaptation of road and rail vehicles and their deep cooperation.The ComplexTrans project shows that simply adapting the dimensions and functions of road and rail vehicles can eliminate(or at least significantly reduce)all the problems of existing land transport.The main features of the ComplexTrans system are sufficient parking spaces,reduction of urban and non-urban congestion,electric vehicles with unlimited range and cheaper than standard cars,cheaper and more accessible battery charging,“autonomous ride”,solving the overlap between passenger and freight rail transport and making it self-financing,transferring intercity freight transport to rail,replacing part of continental air transport and many others.The cost-effective and clustered individual transport and individualised public transport of the ComplexTrans system also bring very significant reductions in the risk of transmission of covid-19 and other contagious diseases during transport.展开更多
This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic spee...This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic speeds,the formed shock waves are smeared compared to a conical boattailed projectile.Also,there is a reduction of the wake region behind the triangular base and the rear stagnation point is nearer to the projectile base resulting in base drag reduction.Moreover,there is an improvement of the stability of the triangular boattailed projectile since a lower overturning moment is incurred.展开更多
文摘在阵元数目一定的情况下,为了扩大阵列的孔径,本文采用非均匀稀疏对称阵列,其阵元间距不受四分之一载波波长的限制.为了避免由此带来的角度模糊问题和复杂的二维搜索,本文基于降秩思想,提出了近场源波达方向(DOA,Direction Of Arrival)和距离的无模糊估计方法并且分析了角度估计的模糊性.此方法利用二阶统计量,只需进行一维搜索,且参数自动配对.因此,计算量大大地减少,且在阵元个数有限的情况下,大大地提高了空间分辨率.计算机仿真结果证实了此方法的有效性.
基金This research is partly supported by project SGS-2019-001The 3-D visualisations were prepared by students of University of West Bohemia or by professional designers.
文摘Land transport can no longer meet the requirements.European transport can be described by these words−crowded motorways and cities,dangerous emissions,ubiquitous traffic accidents,delays,expensive railways.Solutions are being sought to transfer a large part of passengers and especially freight transport to(high-speed)rail,and efforts are moving towards electromobility,car-sharing,5G-connectivity,autonomous driving,MaaS(Mobility as a Service)-coordinated transport or hyperloop-type solutions.However,all these solutions have additional challenges and limitations.Solutions are not being searched where they really exist-in the mutual adaptation of road and rail vehicles and their deep cooperation.The ComplexTrans project shows that simply adapting the dimensions and functions of road and rail vehicles can eliminate(or at least significantly reduce)all the problems of existing land transport.The main features of the ComplexTrans system are sufficient parking spaces,reduction of urban and non-urban congestion,electric vehicles with unlimited range and cheaper than standard cars,cheaper and more accessible battery charging,“autonomous ride”,solving the overlap between passenger and freight rail transport and making it self-financing,transferring intercity freight transport to rail,replacing part of continental air transport and many others.The cost-effective and clustered individual transport and individualised public transport of the ComplexTrans system also bring very significant reductions in the risk of transmission of covid-19 and other contagious diseases during transport.
文摘This paper presents a computational study of the air flow past a triangular boattailed projectile.The study shows that there is a single normal shock wave impinges the projectile at transonic speeds.At supersonic speeds,the formed shock waves are smeared compared to a conical boattailed projectile.Also,there is a reduction of the wake region behind the triangular base and the rear stagnation point is nearer to the projectile base resulting in base drag reduction.Moreover,there is an improvement of the stability of the triangular boattailed projectile since a lower overturning moment is incurred.
